Keynote and Plenary Talks:
Presidential Lecture: Making up your mind: the intimate dependence and remarkable precision of cortical interneurons – Gordon Fishell, Harvard Medical School
Classic work from two decades ago demonstrated that inhibition is mediated through an array of over 50 discrete cortical cell types. Each of these possess unique shapes and properties, suggesting that they have specific roles in the brain. Despite this, our understanding of how such inhibitory neuron diversity is generated and assembled into functional cortical circuits is lacking. Parvalbumin and somatostatin interneurons, the two largest populations of inhibitory cortical cells are generated in a specialized region of the subcortex, known as the medial ganglionic eminence. Amazingly, both these cell types migrate during development across the brain to form canonical circuits with excitatory cortical cells. By studying their gene expression during their incorporation into cortical circuitry, we have discovered key regulators of their development, which provided us with the tools to interrogate the different subtypes and witness and perturb their development. These advances provided the tool kit to start tackling two big questions. How do these cells find their right excitatory cell partners in the brain and just how selective are these connections? In this talk, I will focus on the somatostatin populations, which we have recently found selectively connect to different excitatory populations, with one type targeting corticofugal cells and the other targeting intercortical relay neurons. Moreover, it seems these relationships depend on excitatory cells providing signals to the interneurons when they arrive in the cortex. The output and relay excitatory cells, which reside in different layers, appear to provide “instructions” to somatostatin cells as they settle within the cortex, allowing them to literally “learn on the job”. This indicates the existence of a lock and key specificity in connectivity that we are only beginning to understand.
Featured Plenary Speaker 1: Decoding Parkinson’s disease – Valina Dawson, John Hopkins
Institute of Institute for Cell Engineering, Departments of Neurology, Neuroscience and Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Parkinson’s disease is characterized by the pathologic accumulation of misfolded α-synuclein protein leading to intracellular inclusions (Lewy bodies and Lewy neurites). PD presents with both motor and non-motor symptoms, with the motor symptoms largely due to the loss connectivity within the motor circuit of dopamine neurotransmission from the substantia nigra par compacta leading to a rest tremor, slowness of movement, rigidity, and postural instability. The non-motor symptoms of anxiety, depression, sleep disorders, autonomic dysfunction, constipation, and cognitive impairment are related to pathologic α-synuclein affecting other peripheral neurons and brain circuits. Ultimately the devastating symptoms of Parkinson’s disease are due to loss of functional connectivity and neuronal cell death. The pathophysiology of Parkinson’s disease is complex involving mitochondrial dysfunction, disruption of cell signaling, neuronal cell death and neuroinflammation. We will discuss how pathologic misfolded α-synuclein activates and promotes pathogenic cellular processes and how identification of critical molecular pathways can reveal promising therapeutic interventions that could be that could be leveraged into disease-modifying therapies to prevent or slow neurodegeneration in Parkinson’s disease.
Brain Prize Lecture: From CADASIL to other cerebral small vessel diseases. How genetics can inform pathophysiological pathways – Elisabeth Tournier-Lasserve, Université Paris Diderot
Sponsored by the Lundbeck Foundation
Cerebral Small Vessel Disease (CSVD) is a leading cause of ischaemic and hemorrhagic stroke, and dementia. CSVD is caused by various pathological processes affecting cerebral small penetrating arteries, capillaries and/or venules. Two major risk factors, hypertension, and age, underpin most cases. However, the molecular pathways leading to small brain vessels lesions in common CSVD are still largely unknown. In addition to common CSVD, several rare monogenic CSVD have been identified in the last 25 years. The most frequent of them is CADASIL, an autosomal dominant condition caused by highly stereotyped mutations in NOTCH3. The identification of this gene, of the clinical phenotype and cellular/molecular basis of CADASIL was a breakthrough in the CSVD field, opening an avenue to decipher CSVD mechanisms. Later, the tremendous progress of molecular approaches allowed the identification of the genes involved in several additional monogenic CSVD, including HTRA1, COL4A1/COL4A2, CTSA, LAMB1, KCNA5 related CSVD. This continuously expanding group is highly heterogeneous both on a clinical and genetic point of view. There is also a great diversity in the proteins encoded by “CSVD” genes. However, several of these genes encode either extra cellular matrix structural proteins or proteins expressed in the vascular matrisome. In addition, various up- or down- regulating classes of mutations within a given matrisome gene lead to distinct CSVD. Interestingly, variants of some of these genes have been strongly associated with common CSVD. Altogether these data opened avenues to decipher CSVD mechanistic pathways. However, screening of all known CSVD genes in 2022 does not identify a causative mutation in familial cases. Novel network-based computational and statistical approaches using genome-wide data from unrelated CSVD patients are currently used to find the missing genes
Featured Plenary Speaker 2: Rescuing cerebral blood flow deficits in small vessel disease – Mark Nelson, University of Vermont
Cerebral small vessel diseases (SVDs) are a central link between stroke and dementia—two comorbidities without specific treatments. Despite the emerging consensus that SVDs are initiated in the endothelium, the early mechanisms remain largely unknown. Deficits in on-demand delivery of blood to active brain regions (functional hyperemia) are early manifestations of the underlying pathogenesis. The capillary endothelial cell strong inward-rectifier K+ channel Kir2.1, which senses neuronal activity and initiates a propagating electrical signal that dilates upstream arterioles, is a cornerstone of functional hyperemia. Here, using a genetic SVD mouse model, we show that impaired functional hyperemia is caused by diminished Kir2.1 channel activity. We link Kir2.1 deactivation to depletion of phosphatidylinositol 4,5-bisphosphate (PIP2), a membrane phospholipid essential for Kir2.1 activity. Similar results were obtained using an Alzheimer’s disease (5xFAD) mouse model (Mughal, Function, 2021) Systemic injection of soluble PIP2 rapidly restored functional hyperemia in SVD mice, suggesting a possible strategy for rescuing functional hyperemia in brain disorders in which blood flow is disturbed (Dabertrand, PNAS, 2021).
Keynote Lecture: Mechanisms of Axon Growth and Regeneration – Frank Bradke, German Center for neurodegenerative diseases
Sponsored by SickKids Neurosciences & Mental Health Research Program AND the SickKids Garry Hurvitz Centre for Brain & Mental Health
In this lecture, Frank Bradke will discuss his research on how neurons initially polarize to generate and extend their axon. He will then show how his group exploits the underlying developmental mechanisms to elicit axon regeneration in the adult after a spinal cord injury.
Almost everybody who has seen neurons under a microscope for the first time is fascinated by their beauty and their complex shape. Early on during development, however, neurons look round and simple without signs of their future complexity. How do neurons develop their sophisticated structure? How do they initially generate domains that later have distinct functions within neuronal circuits, such as the axon? And can a better understanding of the underlying developmental mechanisms help us in pathological conditions, such as a spinal cord injury, to induce axons to regenerate?
Here, I will talk about the cytoskeleton as a driving force for initial neuronal polarization and axon growth. I will then explore how cytoskeletal changes help to reactivate the growth program of injured CNS axons to elicit axon regeneration after a spinal cord injury. Finally, I will discuss whether axon growth and synapse formation could represent mutually excluding processes. Following this developmental hypothesis helps us to generate a novel perspective on regeneration failure in the adult CNS and to envisage new paths to overcome it. Thus, this talk will describe how we can exploit developmental mechanisms to induce axon regeneration in the adult after a spinal cord injury.
Featured Plenary Speaker 3: Surprising Origins of Sex Differences in the Brain -Margaret McCarthy, University of Maryland
It’s not easy being male. Male fetuses die at a higher rate, are more likely to be born prematurely, more likely to suffer a birth injury, and if they do will fare far worse than females. Postnatally boys are diagnosed with autism spectrum disorders more often than girls, have on average more severe and earlier onset schizophrenia, experience markedly higher rates of attention and hyperactivity disorders and are three times as likely to have language and learning disabilities. This marked gender bias so early in life compels us to understand the biological origins of sex differences in the brain. Animal models free of the complicating influences of gender bias offer the best hope for identifying cellular and molecular mechanisms by which sex differences are established and maintained.
Sex differences abound throughout the brain and range from the macro-, size of entire regions, to the micro-, the average density of synapses along a dendrite, to the mini-, transcriptomic profiles. Androgens derived from the fetal testis drive the sex differentiation process, resulting in a masculinized brain phenotype that will endure across the lifespan. Identifying the mechanisms of androgen mediated masculinization of the brain has been a long-standing goal with recent advances highlighting surprising roles for inflammatory signaling molecules and immune cells. Moreover, membrane derived signaling molecules such as endocannabinoids and prostaglandins play central roles in modulating the behavior of non-neuronal cells such as microglia. Exposure to exogenous substances that intersect with these systems, including cannabis and NSAIDs, can derail normal developmental trajectories if exposure occurs during a critical window. Lastly, inflammation during pregnancy is a major risk factor for development of neuropsychiatric and neurological disorders in the offspring. In this talk recent findings on how the immune system sculpts enduring sex differences in the healthy brain will be reviewed and the implications for disease risk discussed.
New Investigator Award: Boris Bernhardt, McGill University
Sponsored by Neuroscience and Mental Health Institute (University of Alberta)
Plenary symposium 1: Mitochondrial function and dysfunction in Parkinson’s disease: insights from native and model cells
Mechanisms of metabolic dysfunction in synucleinopathies – Scott Ryan, University of Guelph
Neuronal loss in Parkinson’s Disease (PD) is associated with aberrant energy homeostasis and impaired proteostasis in dopaminergic (DA) neurons. Linking these two pathologies is a major hurdle in developing new therapies for PD. It has been proposed that the interaction of α-syn with anionic membranes is critical for neurotransmitter release and vesicle recycling. We thus asked whether a pathophysiological connection between dopamine transmission, metabolic dysfunction and proteostasis exists in PD that centers on the ability of α-syn to interact with mitochondrial and/or synaptic membranes. We utilized a patient-derived human pluripotent stem cell model (hPSC) of PD that allows for comparison of A53T-SNCA mutant neurons against isogenic mutation-corrected controls. Following a floor plate-derived differentiation paradigm to DA neurons, we determined that A53T neurons have decreased levels of dopamine coupled to increased levels of oxidized dopamine in the form of DA-protein adducts leading to increased mitochondrial and proteostatic stress. Using an unbiased -syn-interactome approach we found that in control neurons, α-syn interacts with enzymes important for flux through the pentose phosphate pathway and that this interaction occurs on synaptic vesicles. Moreover, we found that this interaction is lost in the context of A53T-SNCA mutant neurons resulting in a depletion of NADPH and subsequent depletion of glutathione (GSH), a major antioxidant that scavenges DA-radicals. N-acetyl cysteine (NAC) is GSH precursor that is clinically approved and has recently shown benefits in clinical trials against PD. We show that NAC might offer therapeutic benefit in synucleinopathy with respect to normalizing DA levels by increase GSH synthesis. In addition to informing on the mechanism of α-syn mediated toxicity, our data offer insight into protective mechanisms that may offer therapeutic benefit.
Mitochondrial dysfunction in idiopathic Parkinson’s disease, what can patient-derived induced neurons tell us? Janelle Drouin-Ouellet, Université de Montréal
90% of Parkinson’s disease (PD) cases are idiopathic. Although highly heterogenous in their clinical presentation, idiopathic PD cases share a single most important risk factor, which is age. The stem cell-based patient-derived models of PD currently available do not maintain the aging signature at a molecular level, hindering our understanding of this specific aspect of idiopathic PD pathophysiology as these cases are not caused by monogenic mutations and usually develop later in life as compared to familial cases. Recently, we developed a method allowing the direct conversion of skin fibroblasts of PD patients to induced dopaminergic neurons (iDANs), the neuronal type the most affected in PD. Directly reprogrammed neurons maintain critical aspects of the age signature of the donor, including age-related changes in the transcriptome, the reactive oxygen species (ROS) levels, DNA damage, autophagy impairment and mitochondrial dysfunction. As these cellular changes are suspected to play crucial roles in the development of idiopathic PD, we use this model to explore pathophenotypes related to mitochondrial dysfunction in PD patient-derived iDANs. This is done with the aim to provide a new system in which molecular-based stratification of the idiopathic PD patient population can be achieved, with the long-term goal of refining patient selection for clinical trials and for the development of iDAN-based personalized medicine.
Mitochondrial dysfunction in dopamine neurons in Parkinson’s disease: at the interface of cell-autonomous and non-cell autonomous mechanisms – Louis-Eric Trudeau, Université de Montréal
Although some of the key motor symptoms of Parkinson’s disease are known to result from gradual age-related loss of dopamine neurons located in the substantia nigra, the root causes of this cell loss are still unclear. Multiple lines of evidence suggest that mitochondrial dysfunction can act as one of the triggers of this neurodegeneration. This presentation will examine the relationship between mitochondrial dysfunction and neuronal loss in Parkinson’s disease from two different angles. First, evidence will be presented suggesting that the unique morphological and bioenergetic characteristics of nigral dopamine neurons makes them uniquely vulnerable to mitochondrial dysfunction in the context of a cell-autonomous pathological mechanism. Second, this link will be reexamined in the context of very recent work highlighting the possible implication of non-cell autonomous mechanisms initiated by disinhibition of immune responses in genetically susceptible mouse models of Parkinson’s, leading to the attack of dopamine and other vulnerable neurons.
Plenary symposium 2: Neurovascular coupling in health and disease: what we know and what we need to know
Inter-pericyte tunneling nanotubes: at the heart of neurovascular dysfunction in optic neuropathies – Adriana Di Polo, Université de Montréal
Reduced blood flow and impaired neurovascular coupling are recognized features of glaucoma, the leading cause of irreversible blindness worldwide, but the mechanisms underlying these defects are unknown. Retinal pericytes regulate microcirculatory blood flow and coordinate neurovascular coupling through inter-pericyte tunneling nanotubes (IP-TNTs). Using two-photon microscope live imaging of the mouse retina, we found reduced capillary diameter and impaired blood flow at pericyte locations in eyes with high intraocular pressure, the most important risk factor to develop glaucoma. We show that IP-TNTs are structurally and functionally damaged by ocular hypertension, a response that disrupted light-evoked neurovascular coupling. Pericyte-specific inhibition of excessive Ca2+ influx rescued hemodynamic responses, protected IP-TNTs and neurovascular coupling, and enhanced retinal neuron function as well as survival in glaucomatous retinas. Our study identifies pericytes and IP-TNTs as potential therapeutic targets to counter ocular pressure-related microvascular deficits and provides preclinical proof of concept that strategies aimed to restore intrapericyte calcium homeostasis rescue autoregulatory blood flow and prevent neuronal dysfunction
Neurovascular coupling and functional connectivity in Alzheimer’s disease mice: Effects of pharmacotherapy – Edith Hamel, McGill University
Alzheimer’s disease (AD) is a multifactorial disease with cerebrovascular alterations detected before brain structural changes and clinical evidence of dementia. Brain imaging techniques using hemodynamic signals as proxy for neuronal activity during neurovascular coupling (NVC) and functional connectivity are increasingly used for detecting altered brain function related to cognitive deterioration. Using hemodynamic signals of whisker-evoked NVC and resting-state functional connectivity (Rsfc) measured longitudinally together with cognitive testing, we studied disease onset, progression, and response to therapy (simvastatin, SV) in a transgenic mouse model of AD (APP mice). APP mice displayed age-dependent NVC deficits and early alterations in Rsfc in regions associated with the sensory-motor and default-mode (DMN) networks. An increase in Rsfc strength within the DMN was first observed, which was followed by a decrease as disease evolved. SV restored NVC and cognitive decline, and prevented AD-specific alterations within the DMN. The findings, which show reversal of cognitive deficits and altered connectivity by early pharmacotherapy, will be discussed together with effects of a cerebrovascular pathology on both NVC and Rsfc.
Optical dissection of brain pericytes and capillary function during aging – Andy Shih, Seattle Children’s Hospital
Deterioration of brain capillary flow and architecture is a hallmark of dementia. Clinical studies show marked loss of brain pericytes, but whether this is a cause or consequence of capillary defects remains unclear. We conducted cause-and-effect studies in mice by optically ablating pericytes in vivo. Focal pericyte loss in adult and aged mice caused capillary dilation without overt blood-brain barrier disruption. These abnormal dilations altered the distribution of blood cells at capillary junctions, and increased capillary flow heterogeneity in affected areas. Flow disturbance also caused capillary regression and enduring loss of vascular structure. In adult mice, pericyte contact and vascular tone could be restored within days through synergistic remodeling of neighboring pericytes. However, pericyte remodeling was slower in the aged brain, resulting in persistent capillary dilation. These findings establish a link between pericyte loss and disruption of capillary flow and structure. They also suggest that pericyte remodeling is a therapeutic target to preserve capillary function.
Plenary symposium 3: Cannabinoids and endocannabinoids in the context of neurological and psychiatric disorders
Synaptic dysfunction and altered plasticity in Huntington disease: Role of endocannabinoids – Lynn Raymond, University of British Columbia
Synaptic dysfunction underlies early sensorimotor and cognitive deficits and precedes neurodegeneration in a variety of disorders, including Alzheimer, Parkinson and Huntington disease (HD). A monogenic inherited disorder, HD manifests with cognitive, motor and mood disorders associated with progressive degeneration pf striatal spiny projection neurons and cortical pyramidal neurons. Cortico-basal ganglia-thalamic loops regulate movement selection and motor learning, which are impaired early in HD. Skilled motor learning is mediated in part by plasticity at cortico-striatal synapses, including endocannabinoid-mediated, high-frequency stimulation induced long-term depression (HFS-LTD). We found impaired HFS-LTD in pre-manifest HD mouse models, as a result of deficits in HFS-stimulated endocannabinoid synthesis. Inhibition of endocannabinoid degradation rescued HFS-LTD in brain slice recordings and improved skilled motor learning on a rotarod task. These results suggest novel targets for mitigating early symptoms of HD, And support the need for clinical trials to test the efficacy of modulating the endocannabinoid system in treatment of HD.
Supported by the CIHR Fdn-143210 and Huntington Society of Canada
Endocannabinoids, Astrocytes and the Social Transmission of Stress – Jaideep Bains, University of Calgary
Survival requires organisms respond effectively to challenges or stressors. Exposure to stress also leaves a lasting imprint on the brain that may be important in fine-tuning future responses to stress. We have previously shown that stress, as well as the lasting imprint on key synapses in the brain, is transmitted, through social interactions, to others. How this occurs, is not known. Here we show that CB1Rs in the mitochondria of astrocytes in the olfactory bulb are a critical hub for guiding behaviors related to detection of negative affective states and the social transmission of stress.
Endocannabinoids, the Amygdala and the Regulation of Stress and Anxiety – Matthew Hill, University of Calgary
Endocannabinoids are well known to attenuate behavioral and neuroendocrine responses to stress, however the neural circuits through which they exert these effects have not been well established. Work from our lab has identified the amygdala as an important hub for endocannabinoids to modulate stress-related processes. Prompted by this, we have employed a combination of anatomical, chemogenetic and pharmacological approaches to establish amygdala circuits which regulate the stress response and how endocannabinoid signaling is integrated into these circuits. As endocannabinoid based drugs move forward for the treatment of stress-related psychiatric diseases, understanding the mechanisms by which endocannabinoids regulate these processes is essential.
Parallel Symposium 1: Novel Sources of neurogenesis in vivo and in response to neurological injury
PS1.1 Direct neuronal reprogramming by temporal identity factors
Camille Boudreau-Pinsonneault¹, Awais Javed¹, Michel Fries¹, Pierre Mattar², Michel Cayouette¹
¹Institut de recherches cliniques de Montreal, ²Ottawa Health Research Institute
Temporal identity factors are sufficient to reprogram developmental competence of neural progenitors, but whether they can also reprogram the identity of fully differentiated cells is unknown. To address this question, we designed a conditional gene expression system combined with genetic lineage tracing that allows rapid screening of potential reprogramming factors in the mouse retina. Using this assay, we report that co-expression of the early temporal identity transcription factor Ikzf1, together with Ikzf4, another Ikaros family member, is sufficient to directly convert adult Müller glial cells into neuron-like cells, without inducing a proliferative progenitor state. Using genetic lineage tracing, histological, immunohistochemical and scRNA-seq analyses in vivo, we show that the reprogrammed cells arise from Müller glia and share morphological and transcriptional signatures with cone photoreceptors, as well as bipolar cells. Furthermore, we show that co-expression of Ikzf1 and Ikzf4 can reprogram mouse embryonic fibroblasts to induced neurons in culture by rapidly remodeling chromatin and promoting a neuronal gene expression program. This work uncovers general neuronal reprogramming properties for temporal identity factors in differentiated cells, opening new opportunities for cell therapy development.
PS1.2 Recruiting quiescent neural stem cells in the injured spinal cord
Catherine-Alexandra Grégoire¹, Jorge Barreto², Olivier Tastet, Louis-Charles Levros, Loic Cochard, Brianna Goldenstein, Sandra Joppé, Anne Aumont³, Steve Lacroix⁴, Karl Fernandes³
¹Université de Montréa, ²Université Laval, ³Université de Sherbrooke, ⁴CHUL
A central aim of adult stem cell research is to strengthen the regenerative responses of endogenous precursors. In the injured spinal cord, this goal is confounded by the heterogeneous and dynamic nature of the post-injury microenvironment. Here, we identify TGFB1 signaling as an endogenous, injury-induced suppressor of proliferation for ependymal cells, a central canal cell type having the properties of quiescent neural stem cells (NSCs). FoxJ1-expressing ependymal cells undergo complex spatiotemporal changes in proliferation after spinal cord injury (SCI), implying the presence of multiple yet-unidentified regulators. RNA-sequencing of FoxJ1-expressing cells from the intact versus lesioned spinal cord revealed transcription factors and broad classes of transcriptional programs involved in the early responses of ependymal cells to injury. Upstream regulator analysis of these SCI-induced transcriptomic changes suggested a prominent regulatory role for several inflammatory regulators, including TGFB1. Direct administration of TGFB1 to spinal cord stem cells, both in vitro and in vivo, led to a loss of colony-forming ability, identifying TGFB1 is a potent negative regulator of spinal NSC proliferation. Consistent with this, pharmacological inhibition of TGFB1 signaling after contusion SCI restored proliferation in the central canal niche at the lesion epicentre, indicating that endogenous TGFB1 suppresses ependymal cell recruitment at the injury site. These findings provide insight into the regulatory mechanisms controlling ependymal cell responses to SCI and support the concept of targeting specific features of the post-injury microenvironment as a component of strategies to enhance NSC recruitment.
PS1.3 Direct lineage reprogramming strategies for CNS repair
¹University of Toronto
BACKGROUND AND AIM: Direct lineage reprogramming (DLR) is an emerging technology for central nervous system (CNS) repair. DLR aims to replace cells lost to injury or disease by the conversion of other mature cells in the parenchyma. Neuronal loss is characteristic of many types of neurological disease and injury, and therefore DLR strategies aimed at restoring these cells are of significant clinical interest. While there have been many reports of astrocyte to neuron DLR, surprisingly few studies have focused on functional outcomes. With the goal of developing clinically relevant DLR therapies, here we examined the outcomes of astrocyte to neuron DLR in a preclinical model of stroke. METHODS: Ectopic expression of Neurod1, a transcription factor important for neuronal development, was used for DLR in the endothelin-1 mouse model of sensory motor stroke. Adeno associated delivery (AAV5) of Neurod1 and Cre-based cell tracking was used to monitor DLR and the types of neurons produced. In addition, behavioural tests for motor function were performed to assess functional outcomes and compared to rehabilitation (environmental enrichment), the gold standard for stroke therapy. RESULTS: Newly converted neurons (iNs) expressed pan-neuronal markers and expressed appropriate cortical neuron layer markers based on their anatomical position. Importantly, ectopic expression of Neurod1 led to an improvement in motor function, similar to what is seen with rehabilitation paradigms. CONCLUSIONS: We have demonstrated that ectopic expression of Neurod1 in astrocytes leads to functional improvement following stroke. These findings highlight the use of single factor DLR for CNS repair.
PS1.4 Ischemic injury induces reprogramming and local neural regeneration in the adult brain
Margarita Lui¹, Ayden Gouveia¹, Charvi Syal¹, Timal Kannangara², Jean-Claude Béïque², Diane Lagace², Baptiste Lacoste¹, Ling He³, Fredric Wondisford⁴, Jing Wang¹
¹Ottawa Hospital Research Institute, ²University of Ottawa, ³Johns Hopkins Medical School, ⁴Rutgers-Robert Wood Johnson Medical School
Background: Direct in vivo cellular reprogramming has gained much attention for its therapeutic potential to replace lost neural cells in situ following stroke-related brain injury. To translate this new concept into clinical application, it is critical to develop pharmacological approaches that can enhance the in vivo cellular reprogramming process to generate sufficient numbers of mature neurons locally, thus improving the regenerative potential of the damaged brain. Here, we identified that ischemia-activated pericytes (a-pericytes) from the stroke infarct region can be reprogrammed into induced-neural precursors (i-NPCs) both in culture and in vivo, further producing induced-neurons (i-neurons). In addition, we showed that pharmacological approaches targeting a signaling-directed epigenetic pathway, an atypical protein kinase C (aPKC)-mediated Ser436 phosphorylation of CREB Binding Protein (CBP), can modulate the reprogramming/differentiation process. Methods: we used endothelin-1/L-NAME induced focal cortical stroke model, together with multiple tracing tools, to identify local i-NPCs derived from a-pericytes within the stroke lesion site. Results: Using NeuroTrace 500/525 dye (specifically labelling pericytes) and genetic lineage tracing mouse lines (Nestin-cre-ERT2/YFPflx, TBX18-cre-ERT2/YFPflx, NG2-cre-ERT2/YFPflx), we showed that a local population of Sox2+ i-NPCs within the lesion 3 days post-stroke was derived from a-pericytes (NeuroTrace 500/525 dye+, NG2-YFP+ or Tbx18-YFP+), but not from SVZ Nestin-YFP+ NPCs. In addition, we found that permanent deletion of the aPKC-CBP pathway using CBPS436A knock-in mice significantly increased the transient population of Sox2+ i-NPCs shortly after stroke but impaired vascular remodeling and perturbed motor recovery during the chronic phase of stroke. Intriguingly, we identified that compound C, an AMPK inhibitor, was able to facilitate reprogramming efficiency of a-pericytes into i-NPCs both in vivo and in vitro, reminiscent of CBPS436A mice’s phenotype. We further demonstrated that sequential treatment of compound C and metformin in pericyte reprogramming culture can significantly enhance the i-neuron production from pericytes. Conclusion: These findings suggest that targeting the aPKC-CBP pathway to promote reprogramming/differentiation of pericytes into i-neurons is a potential therapeutic approach to regenerate the stroke-damaged brain.
Parallel Symposium 2: The amygdala and the response to reward cues
Sponsored by CERVO Brain Research Centre
PS2.1 Acetylcholine dynamics in the BLA during reward learning
Marina Picciotto¹, Richard Crouse¹
The basolateral amygdala (BLA) is densely innervated by cholinergic fibers from the nucleus basalis of Meynert (NBM). It is increasingly clear that the BLA is important not only for behaviors related to fear learning, but also for learning cue-reward outcomes, and acetylcholine (ACh) has been shown to be important for BLA plasticity and multiple types of learning. We therefore used fiber photometry to measure real-time ACh release in the BLA using a GRABACh sensor as mice learned a cue-reward association in an operant task. We found that reward-related events initially were associated with a peak of ACh release that shifted toward the cue as animals learned the task. We then used an optogenetic strategy to stimulate ACh terminals in BLA and found that it improved cue-reward learning. Surprisingly, stimulation did not have to be contingent with the reward outcome to improve performance, suggesting that the ACh release was not signaling a reward prediction error. This study demonstrates that BLA ACh signaling is important for cue-reward learning, and suggests that ACh release induces plasticity in the structure that does not require release timed to a rewarding event.
PS2.2 Approach behaviours and instrumental pursuit triggered by appetitive cues: role of the basolateral amygdala
Anna Samaha¹, Alice Servonnet¹
¹Université de Montréal
BACKGROUND AND AIM: Environmental stimuli paired with rewards guide animals towards rewards essential for survival such as food, water and safety. These conditioned stimuli (CSs) direct behaviour in two major ways. First, they evoke approach responses, preparing animals to engage with imminent rewards. Second, CSs can become attractive themselves, such that animals will learn new instrumental actions simply to obtain them. Through these effects, cues exert control over psychology and behaviour, promoting reward-seeking actions when the reward is not immediately available. However, when CSs acquire too much control over behaviour, they can promote pathological reward pursuit, as in eating disorders or drug addiction. In a 1st experiment, we examined how the basolateral nucleus of the amygdala (BLA) modulates 1) CS-triggered conditioned approach responses, and 2) the ability of CSs to support the learning of a new instrumental action. In a 2nd experiment we examined how BLA projections to the nucleus accumbens (NAc) core contribute to these effects. METHODS: During Pavlovian conditioning sessions, water-restricted male rats learned to associate a light-tone cue (CS) with water (UCS) delivery into a dish. In Experiment 1 we determined how optogenetic stimulation of ChR2-expressing BLA neurons influences 1) CS-evoked approach behaviors during Pavlovian conditioning and 2) the capacity of the CS to reinforce learning of a new instrumental action (lever pressing). In Experiment 2, we determined how stimulation of ChR2-expressing BLA→NAc core neurons influences these effects. RESULTS: In Experiment 1, during Pavlovian conditioning, pairing CS presentation with stimulation of BLA neurons potentiated CS-evoked water dish visits. This indicates enhanced conditioned approach and appetitive conditioning. During instrumental conditioning sessions, where rats could press a lever to obtain CS presentation (without water), pairing CS presentation with stimulation of BLA neurons also intensified responding for the CS. This suggests enhanced CS incentive value. In Experiment 2, pairing CS presentation with stimulation of BLA→NAc core neurons also potentiated CS-evoked water dish visits during Pavlovian conditioning, but it did not change instrumental responding for the CS. CONCLUSIONS: Increased activity in BLA neurons intensifies CS control over behavior, and this involves 2 dissociable mechanisms. First, by enhancing CS-UCS associative learning. This increases CS-triggered conditioned approach behaviors, preparing animals to engage with the forthcoming UCS. Second, by amplifying incentive motivation to pursue the CS. Furthermore, increased activity in BLA→NAc core neurons specifically is sufficient to promote Pavlovian approach behaviours, without effects on motivation to pursue the CS. The findings reveal new behavioural and psychological mechanisms through which the BLA and its projections mediate the response to reward-predictive cues.
PS2.3 Optogenetic excitation of central amygdala amplifies ‘wanting’ but not ‘liking’ for sucrose reward
Shelley Warlow¹, Daniel Castro², Kent Berridge³
¹University of California San Diego, ²Washington University School of Medicine in St. Louis, ³University of Michigan
The central nucleus of amygdala (CeA) mediates both positively-valenced reward motivation as well as fear. BACKGROUND AND AIM: We have previously found that pairing reward delivery (either a sucrose pellet or intravenous cocaine reward) with optogenetic stimulations of central amygdala amplifies motivation for the paired reward at the expense of an alternative, unpaired reward. We further demonstrate that pairing CeA stimulation with touching an aversive shock rod paradoxically increases shock rod approaches and interactions. But does higher ‘wanting’ imply higher ‘liking’? Evidence so far has been weak. METHODS: To test whether CeA stimulation enhances reward ‘liking’, we used the affective taste reactivity test, in which volume and rate of sweet or other tastes are controlled via intraoral cannula delivery into the mouth of rats. RESULTS: CeA ChR2 laser excitation failed to enhance positive hedonic orofacial reactions or ‘liking’ (e.g., tongue protrusions, paw licking) elicited by sucrose taste, despite enhancing ‘wanting’ in breakpoint measures and narrowly focusing motivation onto the laser-paired sucrose option in a 2-choice task. CeA ChR2 stimulation similarly failed to suppress negative ‘disgust’ reactions to bitter quinine (e.g., gapes, headshakes). CONCLUSIONS: Overall, these findings confirm that CeA ChR2 excitation selectively magnifies incentive motivation and focuses ‘wanting’ narrowly on a laser-paired reward, without enhancing hedonic impact or ‘liking’ for the same sweet reward.
PS2.4 Amygdala mechanisms distinguishing addiction vulnerability phenotypes
Anna Samahah, Shelley Warlow¹, Marina Picciotto²
¹University of California San Diego, ²Yale University
While not all individuals who try recreational drugs develop Substance Use Disorder (SUD), those that do are vulnerable to specific triggers that drive drug seeking even in the face of negative consequences. Preclinical evidence in rats suggests that sign- and goal-tracking individual differences predict differences in drug relapse vulnerability to discrete and contextual cues. These unique relapse vulnerabilities persist despite negative consequences of drug seeking actions. We focus on behavioral flexibility differences of sign- and goal-tracking rats, which are evident both before and after drug experience. We have established that discrete cue-triggered relapse vulnerable sign-tracking rats are less flexible than goal-tracking rats even before drug experience. While extended Pavlovian training promotes sign-trackers’ ability to use state-dependent information to appropriately guide responding to cues, sign-trackers’ persistent flexibility deficits relate to their inability to use cues to infer current outcome value based on prior experience. We’ve recently found basolateral amygdala (BLA) communication with the nucleus accumbens core (NAcC) prevents flexible behavior in sign-tracking rats. When we use chemogenetics to inhibit BLA-NAcC communication, sign-tracking rats show greater flexibility after outcome devaluation. The same manipulation has the opposite effect in goal-tracking rats that rely on BLA-NAcC communication to optimally express their flexible behavioral phenotype. We had originally hypothesized the flexibility of goal-trackers would be mediated by amygdala-cortical projections, and while we find a necessary role for find BLA-insular cortex (IC) communication in the expression of sign- and goal-tracking behaviors, this pathway does not support the behavioral flexibility of goal-tracking rats. In contrast, chemogenetic inactivation of BLA-IC also promotes flexibility in sign-tracking rats, similar to manipulations that disrupt amygdala-striatal communication. Together these results inform our understanding of the brain circuits driving sign- and goal-tracking differences before drug experience, which may aid in circuit investigation of sign- and goal-trackers’ distinct relapse vulnerabilities observed after drug experience.
Parallel Symposium 3: The diverse roles of glia in stress and metabolic disorders
Sponsored by the BRaIN Program at the RI-MUHC
PS3.1 Astroglial endozepines in the hypothalamic control of energy homeostasis
¹CRCHUM-Université de Montréal
In the brain, the hypothalamus plays a key role in the control of appetite and body weight. This control relies on neuronal populations that sense circulating metabolic signals including lipids and activate neuroendocrine and behavioral responses to maintain body weight. Glial cells are now recognized for their key roles in brain energetics, neuronal activity and plasticity. Astrocytes, the most abundant glial cells, are implicated in complex and fundamental behaviours such as breathing and sleeping, and have recently emerged as key players in energy homeostasis. However, the mechanisms by which hypothalamic astrocytes affect energy balance neurocircuitry remain largely unknown. We identified Acyl-CoA Binding Protein (ACBP), also known as Diazepam Binding Inhibitor, as a protein strongly expressed in hypothalamic astrocytes where it regulates the intracellular metabolism of unsaturated fatty acids. ACBP is also secreted and cleaved to generate endozepines including the octadecaneuropeptide which modulate GABAA receptor signaling. We found that hypothalamic ACBP expression is regulated by the metabolic states in a circadian manner. Using targeted ACBP loss-of-function in GFAP astrocytes, we demonstrated that astroglial ACBP deficiency affected meal pattern and body weight without changing total calorie intake in ad libitum fed or refeeding conditions. ACBP KO in astrocytes promoted diet-induced hyperphagia and obesity in both male and female mice, an effect prevented by genetic rescue of ACBP in arcuate astrocytes. Interestingly, mice with astroglial ACBP deficiency were unresponsive to the anorectic effect of oleic acid. The ACBP-derived octadecaneuropeptide selectively activated anorectic/catabolic pro-opiomelanocortin neurons in the arcuate nucleus via a GABAa-independent mechanism and supressed feeding while increasing carbohydrate utilization via the melanocortin system, and induced weight loss in obese mice. These findings uncovered ACBP as a hypothalamic gliopeptide playing a key role in energy balance and exerting strong anorectic effects via the central melanocortin system.
PS3.2 The role of astrocytes in stress-induced cognitive dysfunction
¹Université de Montréal
While stress is essential for survival and adaptation, intense or unrelenting stress particularly when experienced during development can have long-lasting negative effects. Indeed, stress experienced as a child has been shown to increase the susceptibility to anxiety and depression years later, as an adult. This is believed to be due to rewiring of neural circuits, heightening sensitivity to stress and increasing susceptibility to anxio-depressive disorders. While much has been studied regarding the effects of early-life stress on neurons, the contribution of non-neuronal cells which comprise over 50% of all brain cells remains poorly defined. To investigate the effects of early-life stress on astrocytes we used a clinically translatable stress paradigm mimicking maternal neglect during a critical neurodevelopmental window. We show that early-life stress results in persistent modifications in memory as adults, specifically emotional memory. Early-life stress induced a persistent increase in blood glucocorticoids associated with profound changes in astrocyte structure and function into adulthood. Targeting glucocorticoid signalling on astrocytes, we were able to ameliorate the effects of stress on behaviour, underlining the importance of these cells in mediating the central effects of stress. Our data underscore the importance of studying astrocytes in the context of stress to identify new therapeutic targets to treat stress disorders.
PS3.3 Role of the leptin receptor expressing pericyte in energy balance and beyond
Liliia I. Butiaeva¹, Maia V. Kokoeva¹
Our lab recently discovered that a large portion of vessel-enwrapping hypothalamic pericytes express the leptin receptor (LepR) and that selective ablation of pericytic LepR leads to overeating and insensitivity of hypothalamic LepR neurons to circulating leptin. Importantly, we found that intravenously injected fluorescently tagged leptin was specifically retained at LepR pericytes and this retention was attenuated in mice that were deficient in pericytic LepR. Collectively, our data supports the view that LepR pericytes regulate blood vessel permeability in a leptin dependent manner. We now wish to delineate the precise mechanism of how LepR pericytes are engaged in creating localized leaks in the blood brain barrier to facilitate leptin access to hypothalamic LepR neurons and explore the consequences of hyperleptinemia on LepR pericyte function. Ultimately, we expect LepR pericyte to emerge as key link between obesity and certain comorbidities.
PS3.4 Hypothalamic astrocytes in the neuroendocrine control of metabolism
¹Helmholtz Center Munich
BACKGROUND AND AIM: While decades of focused investigations have resulted in major insights into how hypothalamic neurons govern feeding behavior and systemic metabolism, recent work suggest that glial cells such as astrocytes play also active roles in regulating whole-body energy homeostasis. Thus, my research work is focusing on highlighting this emerging paradigm shift in researching how hypothalamic control of systemic metabolism relies on an appropriate functioning of hypothalamic astrocytes. Specifically, I investigate how impairments in the functionality of hypothalamic astrocytes results in pathological astroglia-neuronal communication leading to a dysregulation in neuronal network activity and impairing the control of metabolism, inducing an overall mishandling of energy that favors metabolic diseases such as obesity. METHODS: To investigate whether hypothalamic feeding circuits require a precise finely-tuned and coordinated communication between astrocytes and neurons for maintaining a balanced control of food intake, body weight and metabolism, I am using the most advanced neuroscience and molecular biological technologies based on: novel transgenic designer receptor mouse models, single cell transcriptomics, hypothalamic cell type specific loss- and gain- of function via adeno-associated viruses, combined with patch-clamp recordings, using transgenic models offering fluorescence-based lineage tracing. RESULTS: So far, my recent findings indicate that hypothalamic astrocytes are responsible for transducing afferent metabolic cues into neuroendocrine actions for the control of systemic metabolism. In this regard, I observed that hypothalamic astrocytes (i) influence the activity of hunger-sensing neurons to adjust feeding; (ii) regulate the accessibility of metabolic cues from the periphery into the brain for controlling systemic hormone sensitivity; (iii) exhibit diverse responses to hypercaloric diets that might be defined by their functional heterogeneity in the control of metabolism; and (iv) are key for the regulation of pre-autonomic hypothalamic centers to modulate peripheral organ function. CONCLUSIONS: Overall, my findings support that hypothalamic astrocytes are key elements in the neuroendocrine control of metabolism and represent potential cellular targets to inspire and enable novel therapeutic strategies to fight obesity.
Parallel Symposium 4: Neuronal dynamics underlying memory in the input and output structures of the hippocampus.
PS4.1 Not just a compass: the role of the head-direction system in learning and memory during sleep
The head-direction (HD) signal is a crucial piece of information for navigation. It is processed by a population of HD neurons each coding for a specific direction of the head, the population of HD neurons thus being akin to a compass for the brain. This signal is conveyed from the anterodorsal nucleus (ADN) of the thalamus to the spatial navigation system in the entorhino-hippocampal region where spatial signals are represented, for example, by place and grid cells. During sleep, hippocampal place cells reactivate patterns that form with spatial learning, a phenomenon that is instrumental for memory consolidation. However, whether inputs to the hippocampus such as HD cells influence hippocampal activity during sleep remains unknown. Here, I will show that, during sleep, the HD cell population remains organized as during wakefulness in the ADN. In addition, the ADN-HD cell population reactivates coactivation patterns that form during recent spatial learning and this organized population activity influences downstream structures in the entorhino-hippocampal system. In conclusion, these findings shed light on subcortical processes at play for long-term memory formation.
PS4.2 A cross-network oscillatory motif underpinning cocaine-paired memory retrieval
¹University of Oxford
Memories of drug experience invigorate behavioural actions biased towards drug-paired stimuli. These maladaptive memories engage many brain regions; however, the patterns of inter-region coordination that relate to cocaine-paired memory retrieval remain elusive. In this talk, I will be presenting ongoing work reporting a brain-distributed motif of cooperative network oscillations that underlies dynamic retrieval of cocaine-paired memory. By simultaneously recording oscillatory activity in the prefrontal cortex, nucleus accumbens, amygdala, hippocampus and ventral tegmental area of the mouse brain, I will describe a higher-order, cross-network pattern of beta-band oscillatory activities that report initial recall of cocaine-paired memory, and its subsequent renewal following extinction. I will further discuss evidence that such beta-specific patterns of oscillatory coordination are organised by ventral tegmental area 4-Hz oscillations. Binding together a set of distributed brain networks in this manner may underlie the robustness of drug-paired memories, and hence the resilient nature of drug seeking behaviour.
PS4.3 Prefrontal neuronal dynamics supporting memory integration and transformation
¹University of Toronto
BACKGROUND AND AIM: As memories become old, incidental details unique to each memory are mostly forgotten, whereas common latent patterns are retained. This process is thought to build generalizable knowledge of the external world, which allows for predicting adaptive behaviour in a similar new situation. Recent evidence in humans and rodents suggests that the integration and prediction processes critically depend on the medial prefrontal cortex (mPFC); however, how these processes are implemented in real-time neuronal ensemble dynamics remains unknown. METHODS: We recorded spiking activity in the prelimbic region of the mPFC while rats underwent context-dependent differential associative learning tasks. RESULTS: In the first study, the rats learned two distinct stimulus associations across several weeks. During this period, firing patterns of mPFC neurons became less selective for sensory features unique to each association while becoming more selective for their common relational feature. Notably, the patterns of increased relational coding followed time courses different from those of decreased sensory coding, implying that building abstraction is not merely a product of selective forgetting. We then conducted the second study to investigate the utility of the abstract, gist-like representations in the mPFC. Rats initially learned a “rule” that one of two neutral conditioned stimuli (CS1, 2) preceded eyelid shock in each of two rooms. On the test day, the divider between the two rooms was removed for the first time, allowing the rats to move between the rooms freely. When one of the CS was presented in a block, the rats successfully avoided the shock by moving to the room where the current CS had not been paired with the shock. This new goal-directed behaviour was not observed in other rats that did not learn the rule beforehand, suggesting that it arose from the transformation of the learned rule but not from the real-time acquisition of place aversion. Furthermore, immediately before the rats expressed the new goal-directed behaviour, mPFC neuron ensembles spontaneously reactivated the firing patterns associated with the learned rule. The timing of this spontaneous reactivation was tightly coupled with the initiation of the goal-directed behaviour. CONCLUSIONS: These findings suggest that the mPFC network possesses a unique coding property that allows extracting commonality across multiple experiences and transforming it to infer new adaptive behaviour.
Parallel Symposium 5: Alternative splicing in the health and disease of the mammalian brain
PS5.1 Cell-specific epigenetic control of calcium ion channel splicing and function
- Javier Lopez Soto¹, Diane Lipscombe²
¹North Carolina State University, ²Robert J. and Nancy D. Carney Institute for Brain Science. Brown University
BACKGROUND AND AIM: Voltage gated CaV2.2 channels are crucial gatekeepers between peripheral detection of noxious stimuli and central perception of pain. They are located at points of sensory detection in nociceptors and control transmission of noxious stimuli at nociceptor termini in the dorsal horn spinal cord. CaV2.2 channels are the targets of many drugs and neurotransmitters that activate G-protein coupled receptors to down regulate nociception. Nociceptors express a unique form of the CaV2.2 channel, through alternative splicing, which influences the sensitivity of CaV2.2 channels to inhibition by μ-opioid receptors. Our goal is to elucidate the mechanism of cell-specific alternative splicing of Cacna1b, the gene encoding CaV2.2 channels, exon 37a to allow the expression of a unique isoform of CaV2.2 in nociceptors that confers high sensitivity to morphine. METHODS: We investigate binding of CTCF to DNA using the electrophoretic mobility shift assay and chromatin inmunoprecipitation (ChIP) followed by qPCR. We use F11 cells and dorsal root ganglia (DRG) cells from the TRPV1tdTomato mouse strain, and quantify exon expression and DNA methylation by qPCR and bisulfite sequencing in nociceptors. RESULTS: We find that cell and exon-specific DNA hypomethylation permits CTCF binding, the master regulator of mammalian chromatin structure, which, in turn, controls splicing in the DRG-derived F11 cell line. We identify that CTCF binds Cacna1b exon 37a in several human and mouse cell lines. By electrophoretic mobility shift assay, we confirm that recombinant CTCF binds exon 37a, but not the neighboring homologous exon 37b. We have applied several methods to show that CTCF promotes Cacna1b exon 37a inclusion in Trpv1-lineage nociceptors during alternative splicing. In F11 cells, we show: 1) by ChIP-qPCR, that CTCF binds in exon 37a of Cacna1b in vivo, but not in exon 37b; 2) CTCF overexpression increases, and CTCF siRNA knockdown decreases exon 37a inclusion; 3) pharmacological inhibition of gDNA methylation, with 5-azacitine, increases exon 37a expression; and 4) CTCF siRNA knockdown occludes 5-azacitidine exon 37a increase. In mice, we show that DRG Trpv1-lineage nociceptors express exon 37a and have less methylation in locus 37a compared to DRG neurons that do not express Trpv1. Additionally, we find that following peripheral nerve injury exon 37a inclusion is reduced and methylation levels increased in comparison with sham controls. CONCLUSIONS: Our results show that hypomethylation of exon 37a, specifically in Trpv1-lineage nociceptors, likely permits CTCF binding and expression of CaV2.2 channel isoforms with increased opioid sensitivity in mice. Following nerve injury, exon methylation is increased and splicing is disrupted. Our studies define the molecular mechanisms of cell-specific alternative splicing of a functionally validated exon in normal and disease states and reveal a potential target for the treatment of chronic pain.
PS5.2 Gain control of LTP and learning by alternative splicing of the GluN1 subunit of NMDA receptors
Ameet Sengar¹, Michael Salter¹
¹Hospital for Sick Children
NMDA receptors are crucial ionotropic glutamate receptors playing key roles in developmental, physiological and pathological processes in the central nervous system. These receptors are heterotetramers comprised of two glycine-binding GluN1 subunits and two glutamate-binding GluN2 subunits. GluN1 is encoded by a single gene, GRIN1, with 8 splice variants. Conventional wisdom is that GluN1 subunits do no more than bind glycine as a co-agonist with glutamate and are necessary for the proper assembly and surface delivery of the receptors. Although the splice variants were identified shortly after GRIN1 was discovered, the biological function of alternative splicing of GRIN1 remained unresolved. Recently, dysregulation of splicing of GRIN1 transcripts containing the alternatively spliced exon 5, which encodes a highly conserved 21-amino acid cassette (called N1 cassette), has been reported in individuals with autism spectrum disorder. To explore the function of splice variants of GluN1 in vivo, we generated mice lacking exon 5 (GluN1a mice) or constitutively expressing this exon (GluN1b mice). GluN1a and GluN1b mice are viable and develop normally. Ligand potency, magnesium block at -60 mV, Zn2+ inhibition and pH sensitivity were not different by genotype in cultured primary neurons from these mice. But, the presence of the N1 cassette did alter allosteric regulation. Namely, spermine increased NMDA evoked currents in GluN1a neurons whereas currents were reduced by spermine in GluN1b neurons. Similarly, 10 mM Mg2+ increased NMDA evoked currents at +60 mV in GluN1a neurons whereas Mg2+ reduced NMDA currents in GluN1b neurons. Using iPSC-derived neurons generated from an individual with autism spectrum disorder, we also observed increased Mg2+ potential of NMDA evoked currents which was consistent with the results from mouse neurons lacking the GluN1 N1 cassette. To explore the role of the N1 cassette in synaptic NMDA receptors, we recorded field excitatory postsynaptic potentials (fEPSPs) at Schaffer collateral – CA1 synapses using hippocampal slices from GluN1a and GluN1b mice. We found that fEPSP amplitude responses to increasing stimulation intensity, paired pulse ratio and NMDA:AMPA receptors ratios were all not different by genotype. However, long-term potentiation induced by theta burst stimulation was significantly lower in GluN1b slices. To assess if the N1 cassette might also affect NMDA receptor dependent learning and memory, we tested each genotype in the Morris water maze. GluN1a mice learned more quickly and had significantly better recall than did GluN1b mice. Unexpectedly, GluN1a mice performed better than wild type mice. Thus, our report answers a long-standing question in neuroscience by demonstrating a biological function of alternative splicing of GRIN1. Funding from CIHR, Ontario Brain Institute and the Simons Foundation for Autism Research.
PS5.3 Alternative splicing of AMPA receptor signalling complexes
Amanda Perozzo¹, Derek Bowie¹
BACKGROUND AND AIM: AMPA-type ionotropic glutamate receptors (AMPARs) are fundamental for fast excitatory neurotransmission across all brain regions. These cation-permeable channels consist of four pore-forming subunits, each of which can be alternatively spliced. Alternative splicing occurs in the ligand-binding domain (LBD) at a region called the ‘flip/flop cassette’, generating two splice variants: flip and flop. The expression pattern of flip and flop in the CNS is highly controlled, both spatially and temporally. Furthermore, flip and flop isoforms exhibit distinct pharmacological and kinetic properties and also differ in their responsiveness to allosteric modulators. Recent work from our lab has shown that alternative splicing of AMPARs unexpectedly dictates the intrinsic nanoscale mobility of the apo state. In the absence of agonist, flop receptors are inherently more mobile than flip receptors, which underlies differences in the time course of channel activation and sensitivity to allosteric regulation. In the brain, AMPARs do not act alone; they form signalling complexes with auxiliary proteins which modify their functional behaviour. Given this, we wondered whether AMPAR alternative splicing can also impact modulation by auxiliary subunits. METHODS: For recombinant experiments, we transiently co-expressed alternatively spliced AMPA receptor pore-forming subunits and auxiliary subunits in HEK293 cells. For native experiments, we prepared acute sagittal slices of mouse cerebellar vermis. We then performed electrophysiological recordings on excised membrane or nucleated patches using a fast perfusion system to measure channel gating properties. RESULTS: We find that one of the most prominent auxiliary subunits, transmembrane AMPAR regulatory protein gamma-2 (TARP γ2) is unable to regulate the time course of desensitization of flop receptors. In contrast, another important auxiliary subunit, Cornichon-3 (CNIH-3) is completely unaffected by alternative splicing. Our data suggest that this distinction can be explained by both structural and kinetic mechanisms. TARPs and CNIHs target different AMPAR gating modes, where TARPs act to slow desensitization via LBD interactions, while CNIHs primarily affect deactivation via the transmembrane region. Since alternative splicing also targets the AMPAR LBD to regulate desensitization, the flip/flop cassette dominates and acts as a master switch to selectively override TARP function. In addition, we show that other auxiliary protein families, namely GSG1L and CKAMP44, are unaffected by alternative splicing. Importantly, we extend our findings to the native system and demonstrate that the flip/flop cassette regulates fully- and partially-TARPed AMPARs in the cerebellum. CONCLUSIONS: Altogether, this work establishes that AMPA receptor alternative splicing is a complex regulatory mechanism that, in coordination with auxiliary subunit association, fine-tunes and diversifies synaptic transmission.
PS5.4 A splicing code reveals an expanded landscape of brain microexons with direct genetic links to autism
Hannes Bretschneider¹, Guillermo Parada¹, Jack Li¹, Ulrich Braunschweig¹, Mingkun Wu¹, Brett Trost², Stephen Scherer³, Quaid Morris⁴
¹University of Toronto, ²The Hospital for Sick Children, ³The Hospital for Sick Children and University of Toronto, ⁴Memorial Sloan Kettering Cancer Centre
BACKGROUND AND AIM: Alternative, neural 3-27 nt-long microexons have emerged as a critical regulatory hub in nervous system development and higher order cognitive functioning that is frequently disrupted in neurological disorders. Previously, neural microexons were largely detected using RNA-seq data from intact brain tissue. As such, microexons spliced in relatively rare cell types or weakly expressed genes may have been missed. Moreover, cis-elements important for microexon splicing have not been systematically defined, and whether these elements are directly disrupted by variants with causative roles in neurodevelopmental disorders has not been determined. METHODS: We have developed a machine learning model that reliably predicts neural microexons from input genomic sequence. We have combined this predictive code with MicroExonator, an RNA-Seq analysis tool for the de novo discovery and quantification of microexons. By performing in silico saturation mutagenesis, we have further used the code model to pinpoint sequences critical for splicing of known and novel microexons, as well as autism-associated variants that disrupt these elements. RESULTS: Applying MicroExonator to thousands of brain RNA-Seq datasets confirms more than 1,600 code-predicted novel microexons in human, most of which are detected in brain single cell RNA-Seq data. This expanded repertoire includes numerous examples that have neural cell type-specific splicing patterns, and many that elicit mRNA turnover and are controlled by previously unknown regulatory mechanisms. Applying the code to predict the impact of autism-linked variants compiled from the Simons Simplex Collection indicates that probands have a significantly higher burden of rare singleton microexon-associated variants than unaffected siblings. Remarkably, many proband-specific variants disrupt the splice sites of microexons, as well as critical RNA binding recognition motifs located distally from splice sites, both in autism-linked genes and genes not previously known to have causative roles in neurological disorders. CONCLUSIONS: Our results provide a greatly expanded atlas of brain microexons, demonstrate a direct impact of autism-associated genetic variation on this splicing program, and further uncover new genes and mechanisms linked to neurological disorders.
Parallel Symposium 6: Understanding dynamic neural circuit activity during defensive behavior with optical recording methods
Sponsored by CERVO Brain Research Centre
PS6.1 Serotonergic modulation of ventral hippocampus underlies sex-related differences in anxiety
Bénédicte Amilhon¹, Félix Perreault¹, Fiona Henderson¹, Anne-Sophie Simard¹, Suzanne van der Veldt¹, Guillaume Ducharme¹
¹Université de Montréal / CHU Sainte-Justine Research Center
BACKGROUND AND AIM: Anxiety disorders disproportionately affect women, yet the neural substrates underlying sex-related differences in anxiety have been largely understudied. Our work focuses on the ventral hippocampus network and serotonergic neurons from the raphe nuclei, two key players in the modulation of anxiety levels. METHODS: Using retrograde viral vectors, we targeted the expression of fluorescent reporters, optogenetic tools or calcium sensors to the sub-population of serotonergic neurons that send monosynaptic projections to the ventral hippocampus. RESULTS: We show that selective optogenetic activation of ventral hippocampus-projecting serotonergic neurons increases anxiety levels in female, but not male mice. I will discuss the dynamics of serotonergic neuron activity in relation to aversive environment exploration, measured using fiber photometry. In addition, I will also present some of our recent results addressing the effects of serotonin on ventral hippocampus theta rhythm, a network state related to anxiety-like behavior. CONCLUSIONS: These studies highlight sexual dimorphism in the raphe-ventral hippocampus serotonergic pathway and provide novel insight about the neural circuits underlying increased vulnerability to anxiety in females.
PS6.2 Sex differences in neural representation of threat in ventral hippocampal and prefrontal cortical projections to nucleus accumbens
Jessie Muir¹, Eshaan Iyer¹, Karen Wassef¹, Sarah Gostlin¹, Rosemary Bagot¹
BACKGROUND AND AIM: Although fear is essential for survival, excessive fear is implicated in a range of neuropsychiatric disorders. The nucleus accumbens (NAc) plays a role in learning about and behaviorally responding to appetitive and aversive stimuli by integrating input from several brain regions including the ventral hippocampus (vHIP) and prefrontal cortex (PFC). Here we investigate how neural activity in these projections is shaped by aversive experiences and how it guides defensive behavior in response to threat. METHODS: Using frame-projected independent fiber photometry (FIP) to image in vivo calcium activity in male and female mice, we recorded PFC and vHIP NAc-projecting neurons during a Pavlovian fear conditioning paradigm in which mice encountered both threat cues (CS+) predicting shock and neutral cues (CS-) with no outcome. RESULTS: Neural activity in both the vHIP-NAc and PFC-NAc encodes foot-shock and differentiates threat-predictive from neutral cues in a sex specific manner. Foot-shock increased activity in both pathways with response in PFC-NAc augmented in females compared to males. These projections showed pathway and sex specific increases at cue onset with vHIP -NAc being elevated in males but not females and PFC-NAc being elevated in females but not males while both pathways exhibited suppression in anticipation of shock. Although both pathways respond to and discriminate threat predicting and neutral cues, neural representations did not predict freezing behavior. Consistent with this lack of relationship, pathway-specific chemogenetic inhibition did not impair cue-induced freezing. Given the role of the NAc in shaping motivated behavior, we examined if these NAc inputs might contribute to suppression of reward seeking by fear conditioned cues. Using a conditioned suppression paradigm in which aversive cues were presented while mice lever press for reward, we found that pathway-specific chemogenetic inhibition attenuated suppression of lever pressing by the CS+ in a sex-specific manner. CONCLUSIONS: Our findings suggest that both the vHIP and PFC convey information about threat prediction to the NAc medial shell to guide ongoing behavior with pathway-specific sex differences in neural encoding that may relate to sex differences in threat processing and risk for psychiatric disorders such as anxiety and depression.
PS6.3 Synaptic transmission at the lateral habenula neural outputs in normal and pathological conditions
The lateral habenula (LHb) is an important part of the reward circuit as it provides ‘negative value’ signals: when an animal receives a reward that is less than expected (i.e. is disappointed) or anticipates punishment (i.e. expects something bad), the LHb is active. This information is thought to be used to shape future behavior so as to maximize reward and avoid unpleasant events. An individual with overly active LHb, such as in major depression, would be expected to be easily or continually disappointed and generally expect bad outcomes. The LHb receives inputs from the basal ganglia and the limbic system, and projects to aminergic midbrain centers including the serotoninergic dorsal raphe nucleus (DRN) and the dopaminergic ventral tegmental area (VTA), and also to the rostromedial tegmental nucleus (RMTg), a GABAergic nucleus strongly inhibiting dopamine centers. However, the contribution of individual LHb inputs and outputs in signal processing to control behavior, and how their dysfunctions may contribute to major depression is still elusive. Our previous work has shown that the pathway from the LHb to the RMTg plays an important role in motivational control, where its activation reduces motivation to exert effort. To examine potential alteration in synaptic transmission in this pathway in depression, we examined how chronic stress may impact synaptic transmission at this pathway. To this aim, we expressed ChR2 in the LHb, submitted mice to chronic social defeat stress (CSDS), and characterized synaptic transmission in the RMTg from control and stressed mice using whole-cell recordings. Similar approach has been used to also characterize transmission at the DRN and VTA pathways. At the LHb-RMTg synapses, CSDS increased presynaptic transmission (decreased paired-pulse ratio) compared to control mice. At the LHb-DRN synapses, chronic stress did not change presynaptic transmission (PPR) but increased postsynaptic transmission (increased evoked AMPAr/NMDAr ratio) in susceptible mice. A large fraction of the potentiated neurons in the DRN were serotoninergic and clustered in a specific anteromedial subdivision of the DRN. Finally, at the LHb-VTA synapses, CSDS decreased AMPAr/NMDAr ratio in susceptible mice while no change was observed for the PPR. Interestingly, we also found that VTA-projecting neurons were less active in susceptible mice suggesting a hypofunctional reward circuit encompassing the LHb-VTA pathway. Taken together, these results suggest that the LHb neural outputs are differently altered following CSDS, and these synaptic changes may have distinct contribution to the development of maintenance of symptoms found in depressive disorders.
PS6.4 Dorsal hippocampus neuronal activity during context fear discrimination
¹University of Toronto – Scarborough
BACKGROUND AND AIM: Assessing an environment as safe or dangerous is critical for our survival and impairments in this process are a central criterion of post-traumatic stress disorder (PTSD). To develop treatments for PTSD, an understanding of the neuronal circuit activity that supports spatial representations and fear expression are necessary. METHOD: Here we investigate context fear discrimination using single-photon in vivo microendoscope calcium imaging in freely behaving mice during a novel context retrieval task. Using a cylindrical LED screen as a conditioning apparatus, we presented different visual contexts while mice remained in the same physical space. Mice were fear conditioned to visual context A in the AM and presented neutral context B in the PM. During the context memory retrieval test, mice were placed in the apparatus and context A and B presentations were repeatedly alternated while hippocampal activity and fear behaviour were recorded. RESULTS: We report three primary findings. During context fear memory formation, the hippocampal spatial map for context A is altered. Furthermore, “teleporting” mice between threatening context A and neutral context B is associated with dynamic alterations in the hippocampal spatial map. Finally, as spatial maps for threatening and neutral contexts become more distinct, context fear discrimination becomes stronger. CONCLUSIONS: Together these findings illustrate the dynamic hippocampal activity associated with context fear discrimination and provide a framework to understand how spatial representations are linked to emotional behaviors.
Parallel Symposium 7: Cueing Factors in Addiction
Sponsored by the Djavad Mowafaghian Centre for Brain Health
PS7.1 Morphine learned as an interoceptive stimulus causes sex- and task-dependent alterations in subsequent morphine reinforcement and reward in rats.
Jennifer Murray¹, Allyson Andrade¹, Caitlin Nolan¹, Adiia Stone¹
¹University of Guelph
Introduction: Research on drugs of abuse typically focuses on their reinforcing or rewarding effects and how surrounding proximal and distal cues can trigger drug seeking and taking behaviours. However, drugs also elicit internally perceived (interoceptive) stimuli that can be used as cues to guide appropriate behaviour, including how and when to seek food. Our research program investigates how such interoceptive cue-dependent learning with the mu opioid receptor agonist morphine can alter the subsequent value of that drug. Methods: Morphine is trained to disambiguate when a discrete exteroceptive auditory conditioned stimulus (CS) is predictive of a sucrose unconditioned stimulus (US). Male and female rats are injected with morphine or saline 15min before each 20min session. Every session contains 8 CS presentations. For feature positive (FP) training, morphine (3.2mg/kg) indicates when the CS-US contingency is active; on intermixed saline sessions, the US does not follow the CS. For feature negative (FN) training, the contingencies are reversed. Rats learn to seek sucrose during the CS presentations on appropriate sessions. Three recent studies have built on this effect: First, following discrimination training, we assessed the effects of the learning on morphine reinforcement by fitting rats with IV catheters to self-administer morphine (0.5mg/kg/infusion). Second, in a separate cohort, following discrimination, we assessed the effects of the learning on morphine reward by then shifting them to place conditioning. Under the standard discrimination training procedure, contingency learning can only be assessed on the first trial of each session, obfuscating the pattern of learning across the remaining trials. Therefore, in the third study, rats assigned to FP or FN groups underwent one-trial training in which a single CS was presented in each session. Results: In all standard discrimination training studies, rats were able to disambiguate morphine from saline conditions. Following training, FP male, but not female, rats self-administered more morphine, sought more morphine under extinction conditions, and showed greater reinstatement than FN rats. Conversely, there was no development of morphine conditioned place preference in FN female, but not male, rats. Finally, when assessing the development of the discrimination on a trial-by-trial basis, we are so far observing few differences between training contingency based on sex. Implications: These findings indicate that a prior appetitive or explicitly non-appetitive learning history with the stimulus effects of a drug of abuse can alter its subsequent reinforcement and rewarding value in a sex-dependent manner. Particularly in the case of opioid analgesics, such a finding has important implications for how such interoceptive stimuli may be differentially processed following drug experience in humans.
PS7.2 Interoceptive correlates of acute alcohol administration and future clinical avenues
Mateo Leganes-Fonteneau¹, Jennifer Buckman¹, Marsha Bates¹
Interoception, the integration of bodily states in the brain, is hypothesized to support alcohol-related behaviors. However, there is little evidence on how cardiac interoceptive processes are affected by acute alcohol administration. Two sets of published studies examined how alcohol-induced changes in interoception shape alcohol-related responses. In two experiments (n=50, n=31) we found that alcohol modulates participants’ ability to feel their own hearts, and that these changes correlate with perceived alcohol effects and mood changes. Further, changes in interoception correlate with anticipated effects of alcohol, as an index of alcohol expectancies. We propose that alcohol-induced interoceptive experiences build, over the course of drinking history, an expectancy about alcohol effects. These expectancies are in turn crucial for future drinking behaviors. Heart-rate variability indices allow studying the strength of heart-brain communication as a measure of interoceptive signaling. In an initial study (n=168) we found that, in participants with a family history of alcohol use disorder, cardiac signals and memories for alcohol stimuli correlated after alcohol administration. In a second study (n=31) we found that changes in cardiovascular states after alcohol administration correlate with alcohol attentional biases. This implies that alcohol effects on interoception support alcohol priming. These combined results build evidence for different interoceptive pathways underlying positive reinforcement mechanisms in addiction, and can help develop novel treatment and diagnostic tools within the growing field of embodiment and cognition.
PS7.3 Differences in alcohol cue reactivity based on the social context
Samuel Acuff¹, Bruce Bartholow², Jeffrey Sable³, James MacKillop⁴, James Murphy¹
¹The University of Memphis, ²The University of Missouri, ³Christian Brothers University, ⁴McMaster University
BACKGROUND AND AIM: Drinking typically occurs in social settings, and emerging adults are more likely report binge drinking on nights with friends compared to nights when they are alone. However, those who report more solitary drinking episodes tend to have greater problems and an increased risk for alcohol use disorder. Behavioral economics suggests that heavy alcohol use may be most likely when the value of alcohol outweighs the costs. It is important to understand social effects on alcohol value, in addition to individual differences, which may explain variations in patterns of solitary drinking. Previous research found a 50% increase in alcohol value, using behavioral economic demand curves measured with alcohol purchase tasks, in a social, compared to solitary, drinking condition. Further, the difference in value across conditions predicted alcohol problems. It is unclear whether these findings correspond with underlying biomarkers of reward, creating a barrier in understanding behavioral and biological risk pathways. One biomarker candidate is the event-related potential known as the P3, which is thought to reflect the incentive value of the eliciting stimuli. Harmful alcohol use is associated with greater P3 reactivity to alcohol than to neutral cues. However, no study has examined relations with alcohol demand, and little work has examined P3 reactivity to alcohol under social conditions compared to alcohol alone. METHODS: Mr. Acuff will present data from emerging adults (current n=37; anticipated N=60) who completed an oddball task during an EEG session and a solitary and social alcohol purchase task. RESULTS: Consistent with previous research, demand intensity (consumption at zero cost) for the solitary scenario (M=4.69, SD=2.41) was significantly lower than intensity for the social scenario (M=6.26, SD=3.42; Cohen’s d=.66). Further, demand Omax (maximum monetary expenditure during the task) for the solitary scenario (M=20.60, SD=19.54) was significantly lower than Omax for the social scenario (M=27.86, SD=25.17; Cohen’s d=.43). Preliminary analyses of available EEG data suggests greater P3 reactivity to social alcohol cues than to alcohol alone (Cohen’s d=.30), but similar P3 reactivity to social alcohol cues and social nonalcohol (i.e., people hanging out, Cohen’s d=.04). Relations between alcohol demand indices and P3 reactivity to social and nonsocial alcohol cues will be examined in the context of multilevel modeling. CONCLUSIONS: The results suggest that P3 may serve as a biomarker for changes in value that aggregates both alcohol and social value. P3 reactivity across cue conditions was consistent with alcohol demand data, which suggested that alcohol value is greater when drinking with peers than when alone. Additionally, P3 data revealed no difference in reactivity when removing alcohol from a social condition, suggesting that, much of the reward from drinking with friends may come primarily from peer connection.
PS7.4 Contribution of cues to concurrent decision-making
Justin Strickland¹, William Stoops², Cecilia Bergeria¹, Katherine Marks²
¹Johns Hopkins University School of Medicine, ²University of Kentucky
Research on drug-related cues has historically focused on how cue exposure impacts measures related to substance use such as drug craving. Less studied in this context is how drug-related cues may impact decision-making between non-drug reinforcers made in events outside of drug-taking episodes. Clinically, changes in decision-making resulting from the presence of drug-related stimuli may help explain cascades of behavior in substance use disorder leading to high-risk activities and negative consequences that were otherwise considered disadvantageous without the addition of a discriminative cue for drug reinforcement. This talk will review recent studies evaluating a novel concurrent choice task designed as a laboratory model of cue-based decision-making. These studies collectively show how choice is a systematic and reliable predictor of substance use risk (e.g., severity of use and use-relate consequences), is specific to drug-cue contexts, and may help identify individual difference variables for individualized treatment. Future research will also be described using these methods in treatment contexts to determine how the value of drug-related cues is altered throughout the course of treatment, and how different treatment modalities may impact changes in value. An interactive demonstration of the task with the audience will be conducted through the use of a mobile compatible task variation.
Parallel Symposium 8: Balancing Tensions between Proprietary Research, Open Neuroscience, and Human Rights
Sponsored by Vision: Science to Applications (VISTA) York University
PS8.1 Primer on patenting of neurotechnologies from the Canadian perspective
Zelma Kiss¹, Ari Rotenberg², Stacey Anderson-Redick¹, Judy Illes²
¹University of Calgary, ²University of British Columbia
Patents turn innovations into protected property to balance the interests of inventors and the public to encourage innovation. The invention must fit into four subject matter categories of process, machine, manufacture, or composition of matter. The innovation must be novel, useful, and non-obvious. It must enable a person of knowledge in the relevant field to practice the innovation; if it is vague such that a practitioner of ordinary skill could not use the information contained therein, and the knowledge common to the profession, to realize the promised useful result, then the patent is invalid. Natural phenomena, abstract ideas, and mental processes cannot be patented. Even if substantial work is put into the discovery of a mathematical formula or a new role for a brain region, neither by itself is patentable. In 2017 we performed a patent landscape analysis that identified brain regions in their claims. We discovered a large increase in such patents granted over recent years, as well as some with unreasonable and overly broad claims. The study led to a larger initiative examining patenting internationally, as part of an ERA-NET (Research Projects on Ethical, Legal and Social Aspects of Neuroscience) NEURON (Network for European Funding for Neuroscience Research) CIHR funded grant called The International Neuroethics Patent Initiative. According to the OECD, between 2008 and 2016, 16,273 patents representing a health-related neurotechnology were filed worldwide, with 58% being filed in the US and 63% about devices/methods for performing neuromodulation. While pure medical methods, or techniques without an associated novel device, are ineligible for patent protection in Canada and most other countries, they are patentable in the US. This has led to many international inventors patenting in the US, including Canadians. Examples will be discussed in the presentation. Medical method patenting may have ramifications on several groups: physicians by restricting the therapeutic tools available to them, patients by slowing release of and preventing access to new treatments, and researchers by limiting the scientific principles they may investigate. Neuroethical considerations are many: a patent that covers all or many practical ways of detecting and modulating the activity of a brain region runs the risk of being a patent on the brain region itself; protecting patent rights prior to proof of scientific validity encourages a patent-first ask-questions-later mentality; inventions that are likely to be most profitable may be developed before those that may do more good; and, using patents as security allows them to devolve to companies that do not necessarily have an interest in health promotion. A system for patenting and marketing new invasive and non-invasive neurotechnologies that balances medical and commercial value, autonomy, and human use protections is critical. Proactive guidance from within the field is essential to achieve this balance.
PS8.2 Insights from the DMCBH Open Science Initiative: an open science buy-in project in action
Jeffrey LeDue¹, Judy Illes¹, Timothy Murphy¹, Paul Pavlidis¹
¹University of British Columbia
The UBC Djavad Mowafaghian Centre for Brain Health (DMCBH) Open Science Initiative is funded by McGill’s Tanenbaum Open Science Institute as an open science “buy-in” project. The initiative launched Dec 1, 2021 and will run for 1 year with the objective to explore local support for open science and a framework that will align the DMCBH with Open Science initiatives at the McGill Neuro, Hotchkiss Brain Institute, Douglas Research Centre, and Western University. The Initiative at UBC is divided into 6 activities that marshal our Centre’s existing strengths in open science and provide the basis and opportunity for iterative consultation, education, and planning. The 6 activities are: 1. A quarterly seminar series 2. Assessments, surveys, and town halls 3. Assessment of the impact of IP and attitudes toward Open Science 4. Open Research training and facilitation, including customized student-driven Databinge events 5. Engagement with university leadership 6. Development of the principles and an implementation plan Activities 1-4 are on-going and will inform Activities 5 and 6 in the second half of the project. Here, we provide an update on Activities 2 and 4. The Initiative’s Open Scholarship Survey is designed for all members of the DMCBH research community regardless of area of specialization, and allows us to capture attitudes, behaviour and perceived norms with respect to key open science practices such as data sharing, code sharing, materials sharing, use of preprints, and open access publishing. Specific questions are posed about the perceived advantages and disadvantages of open science, including the approach to IP. Early results suggest that our community perceives open science as particularly important for neuroscience and is more focused on the perceived benefits to brain health stakeholders than any positive or negative impacts on IP. The ongoing Open Science Practices Needs Assessments are modelled after assessments undertaken in 2019 at UBC to create a resource to assist labs with Data Management and Data Sharing. The assessments consist of guided conversations with key personnel from individual labs (faculty, staff and students) and cover a range of questions from day-to-day data management practices to the active model for data stewardship including ethical, legal and intellectual property concerns. Results support the adoption and enhancement of open science practices through the student driven, data-centric Databinge forum. Overall, we expect a hybrid approach to Open Science at DMCBH that embraces open principles while maintaining individual freedom to pursue some level of IP protection for certain elements of neuroscience progress.
PS8.3 Neuromodulation Patents: a landscape analysis from 2016 through 2020
Ari Rotenberg¹, Anna Nuechterlein¹, Ashley Lawson¹, Stacey Anderson-Redick², Zelma Kiss², Judy Illes¹
¹University of British Columbia, ²University of Calgary
We aimed to analyze the progress of trends in patent construction first characterized by Roskams-Edris et al. (2017) for neuromodulation methods patents granted from 2016 through 2020. We developed a novel, customized search algorithm to scrape Lens.org, an open-access patent database designed to track trends in innovation and return patents in neuromodulation methods. Our approach was based on the presence of combinations of terms associated with the nervous system or its modulation in the text of claims. We applied a content analytical procedure to facilitate a standard review of the claims of each meeting inclusion criteria pertaining to nervous tissue and health-related applications. Results on patents with Canadian inventors, applicants, or owners are reported here. Overall, the algorithm returned 3,065 patents filed with the United States Patent and Trademark Office and European Patent Office. Of the 155 Canadian-driven patents in the sample, 26 met criteria for in-depth evaluation of medical feasibility and ethical considerations. These patents covered a range of techniques in stimulation, ablation, device installation, thermotherapy, and alternative medicine purporting to assess, treat, and monitor an underlying condition with varying degrees of invasiveness. We identified 76 direct references to regions of the nervous system and 136 references to underlying conditions. The terminology of these references did not adhere to any standardized labeling system, causing considerable ambiguity in some cases as to which particular regions or conditions were implicated in the method at hand. The majority of references in both categories were attributed to a small subset of the patents reviewed; one patent alone was responsible for 64 [47%] of references to underlying conditions. Results suggest that while proprietary overreach may be infrequent, it is extreme when it occurs.
PS8.4 Perspectives on intellectual property protections and open neuroscience
Ashley Lawson¹, Ari Rotenberg¹, Anna Nuechterlein¹, Paul Pavlidis¹, Jeffrey LeDue¹, Judy Illes¹
¹University of British Columbia
Patents protect the intellectual property (IP) of innovators for the purpose of establishing unique rights to a product, and enabling widespread adoption and investments for financial gain. In health care, patents conventionally protect innovations involving methods and devices, but protections of naturally occurring products such as human tissue and brain regions have encroached on this domain over the past few years (Roskams-Edris et al., 2017). The principles and intentions of Open Science (OS) may challenge such protections in terms of benefit to research and clinical care, return of value to investors from the public sector such as government agencies, and even opportunities for training new generations of neuroscience leaders and inventors. Here we examined intersections between patenting and OS as perceived by neuroscience researchers, and specifically sought their insights into strategies for non-restrictive IP needed to resolve emerging tensions before they forestall progress. To gather these perspectives, we conducted a series of focus groups with researchers from the Centre for Brain Health at the University of British Columbia. We developed a semi-structured interview guide that covered three major areas: patents in general, patents and open science, patents in neuroscience. Six focus groups and three interviews were conducted in-person and virtually to accommodate researchers’ schedules and University COVID requirements (N=29, 20 men, 9 women). Focus groups were organized according to the patent experience of participants: 11 were patent-experienced; 18 had little or no patent experience. All focus groups and interviews were recorded, transcribed professionally, and de-identified. We used the method of grounded theory to extract major themes Major emergent themes for IP were: advantages of IP, drawbacks of IP, changing IP landscape, conditionally appropriate use of IP, and current IP practices; for OS: advantages of OS, drawbacks of OS, current OS practices, impact of change, and potential for the coexistence of IP/OS; and for Ethical Considerations: cognitive integrity, neuro-exceptionalism, justice, responsibility, and virtue. All told, the data to date suggest that while IP is essential to many researchers, the benefits conferred by OS are significant. Participants suggest that there is no need to eliminate IP within OS, and emphasize potential avenues for hybridization between IP and OS that could mitigate the disadvantages of highly restrictive brain patents. References Roskams-Edris, D., Anderson-Redick, S., Kiss, Z. H., & Illes, J. (2017). Situating brain regions among patent rights and moral risks. Nature Biotechnology, 35(2), 119-121. https://doi.org/10.1038/nbt.3782
Parallel Symposium 9: Systemic Inflammation and the Brain: Interactions with Glia and Neurons
Sponsored by the Djavad Mowafaghian Centre for Brain Health
PS9.1 The danger of brain infections: Microglia cell death is required for optimal immunity to Toxoplasma gondii in the CNS
Samantha Batista¹, Isaac Babcock¹, Maureen Cowan¹, Katherine Still¹, Tajie Harris¹
¹University of Virginia
Control of infection within the central nervous system (CNS) is necessary to protect from damage that is often irreversible. The protozoan parasite Toxoplasma gondii causes a chronic infection of the brain that requires constant immune pressure to control parasite replication. Within the brain, T. gondii transitions to a dormant cyst form. For reasons that are not well-understood, cysts reactivate sporadically endangering neighboring cells. We find evidence of cell death in regions of cyst reactivation and a loss of CNS resident glia. We find that immune cells accumulate in these regions, suggesting that dying cells release factors that attract immune cells to specific locations in the brain. We specifically explored the importance of IL-1α, an alarmin that is expressed by microglia and monocyte-derived macrophages following T. gondii infection. We find that ASC specks form in microglia during infection, consistent with inflammasome activation. Moreover, microglia release IL-1α ex vivo while macrophages do not. The release of IL-1α is dependent on the pore forming protein gasdermin-D and the activity of caspase-1, supporting a role for microglia death by pyroptosis. Mice lacking IL-1α, IL-1R1, caspase-1/11, or gasderminD have higher parasite burdens and defects in the immune response to T. gondii in comparison to wildtype mice. Similarly, we find that deletion of caspase-1 from CX3CR1-expressing cells impacts host control of the parasite in the brain. Together, these results demonstrate that the detection of microglia cell death/damage is necessary to mount an immune response to a pathogen in the CNS.
PS9.2 The potential contribution of systemic inflammation in neuropathic pain
Ji Zhang¹, Wen Bo Sam Zhou¹, Xiang Qun Shi¹, Younan Liu¹, Simon Tran¹, Francis Beaudry²
¹McGill University, ²Universite de Montreal
Background: Neuropathic pain is a complex, debilitating disease that results from injury to the somatosensory nervous system. The presence of systemic chronic inflammation has been observed in chronic pain patients, but whether it plays a causative role remains unclear. Methods: We assessed the protein profile in the serum of mice following the partial sciatic nerve ligation (PSNL) or sham surgery using mass spectrometry-based proteomic analysis. We transferred PSNL or sham serum to naïve mice via intravenous injection and assessed mechanical and cold sensitivity by von Frey and acetone tests. To target a myriad of inflammatory mediators at once, we treated PSNL mice with bone marrow cell extracts (BMCE), having established broad anti-inflammatory properties. Results: Proteomic analysis of mouse serum at 1-day and 1-month following partial sciatic nerve injury (PSNL) or sham surgery revealed that nerve injury resulted in a long-lasting alteration of serum proteome, where the majority of differentially expressed proteins were in inflammation related pathways, involving cytokines/chemokines, autoantibodies and complement factors. While transferring sham serum to naïve mice did not change their pain sensitivity, PSNL serum significantly lowered mechanical thresholds and induced cold hypersensitivity in naïve mice. The treatment of PSNL mice with BMCE not only partially restored serum proteomic homeostasis, but also significantly ameliorated PSNL-induced mechanical allodynia. Serum from BMCE-treated PSNL mice no longer induced hypersensitivity in naïve mice. Conclusions: These findings clearly demonstrate that nerve injury has a long-lasting impact on systemic homeostasis, and nerve injury associated systemic inflammation contributes to the development of neuropathic pain.
PS9.3 The role of ependymal cells in regulating CNS inflammation
Adam Groh¹, Nina Caporicci-Dinucci¹, Brianna Lu¹, Jo Stratton¹
¹Montreal Neurological Institute
Multiple Sclerosis (MS) is the most common demyelinating disease and is characterized by inflammatory and neurodegenerative components, where progressive neurological deficits currently represents the main source of disability. It is now recognized that the grey matter is profoundly impacted, and loss of volume (or atrophy) in deep grey matter (DGM) structures are the most consistent correlates of disease progression. A critical observation is that DGM is subject to atrophy that is more pronounced in areas exposed to cerebrospinal fluid (CSF), suggesting that factors from CSF, such as cytokines, might contribute to DGM damage. As an ECR, my research platform focuses on understanding CSF-associated drivers of neurodegeneration with an emphasis on understanding the involvement of cells that line CSF exposed brain regions, known as ependymal cells in the ventricular system. We have performed advanced single cell transcriptomics and identified several ligand-receptor binding partners relevant to disease. We have also demonstrated that ependymal cells are particularly vulnerable to acute and chronic inflammatory insults, including undergoing gliosis and losing barrier functions. Importantly, we have developed in vitro and in vivo assays to determine which inflammatory factors may be underling these effects. By better understanding the mechanisms underlying disease progression, we aim to discover novel therapy targets to better treat MS.
PS9.4 Versican as a potential inhibitor of remyelination: proposed mechanisms through impeding oligodendrocytes and promoting Th17 cytotoxic neuroinflammation
Samira Ghorbani¹, Emily Jelinek¹, Rajiv Jain¹, Cenxiao Li¹, Brian Lozinski¹, Susobhan Sarkar¹, Deepak Kaushik¹, Yifei Dong¹, Thomas Wight², Soheila Karimi-Abdolrezaee³, Geert Schenk⁴, Jeroen Geurt⁴, Eva Strijbis⁴, Chang-Chun Ling¹, V.Wee Yong¹
¹University of calgary, ²Benaroya Research Institute, ³University of Manitoba, ⁴MS Center Amsterdam
Remyelination failure in multiple sclerosis (MS) contributes to progression of disability. The deficient repair results from neuroinflammation and deposition of inhibitors including chondroitin sulfate proteoglycans (CSPGs). Which CSPG member is repair-inhibitory or alters local inflammation to exacerbate injury is unknown. Here, we correlate high versican-V1 expression in MS lesions with deficient premyelinating oligodendrocytes, and highlight its selective upregulation amongst CSPG members in experimental autoimmune encephalomyelitis (EAE) lesions that model MS. In culture, purified versican-V1 inhibits oligodendrocyte precursor cells (OPCs) and promotes T helper 17 (Th17) polarization. Versican-V1-exposed Th17 cells are particularly toxic to OPCs. In NG2CreER:MAPTmGFP mice illuminating newly formed GFP+ oligodendrocytes/myelin, difluorosamine (peracetylated,4,4-difluoro-N-acetylglucosamine) treatment from peak EAE reduces lesional versican-V1 and Th17 frequency, while enhancing GFP+ profiles. We suggest that lesion-elevated versican-V1 directly impedes OPCs while it indirectly inhibits remyelination through elevating local Th17 cytotoxic neuroinflammation. We propose CSPG-lowering drugs as dual pronged repair and immunomodulatory therapeutics for MS.
Parallel Symposium 10: Sleep perturbations in Alzheimer’s disease patients and animal models
PS10.1 Cognitive, histological, and transcriptional correlates of sleep fragmentation in older adults
¹University of Toronto
BACKGROUND AND AIM: Sleep and circadian rhythm disruption are common in older adults and may have a bidirectional relationship with cognitive impairment and dementia. Here, I will review some of our data relating sleep disruption to dementia-associated brain changes in community-dwelling older adults. METHODS: We studied 1080 older adults from 2 community-based cohort studies of aging. We quantified antemortem sleep and circadian rhythmicity using multi-day wrist accelerometry and cognitive function using a battery of 21 neuropsychological tests spanning 5 domains and then related this to postmortem dementia-related histological findings, and to gene expression in the dorsolateral prefrontal cortex assessed by bulk tissue RNA-seq. RESULTS: Greater antemortem sleep fragmentation is associated with more rapid antemortem cognitive decline, and a higher risk of incident Alzheimer’s disease. As well, it is associated with a higher burden of arteriolosclerosis, a higher burden of neurodegenerative pathologies like levy bodies and neurofibrillary tangles, and greater expression of genes characteristic of aged microglia and activated astrocytes. CONCLUSIONS: Sleep fragmentation is associated with more rapid cognitive decline and multiple dementia-associated neurodegenerative, vascular, and transcriptional brain changes in older adults. Sleep disruption may be a contributor, or marker of, key dementia-associated brain changes.
PS10.2 Ambulatory EEG sleep monitoring in Alzheimer disease: A Pilot Study
Amelia Casciola¹, Meghan Chen¹, Penny Slack¹, Ali Kazemi², Maryam Mirian¹, Jason Valerio¹, Martin McKeown¹, Howard Feldman³, Haakon Nygaard¹
¹University of British Columbia, ²Univ. of California, Davis, ³University of California San Diego
BACKGROUND AND AIM: Sleep disturbances are common in Alzheimer’s disease (AD), with estimates of prevalence as high as 65% across AD and Mild Cognitive Impairment (MCI). A major limitation to a formal, qualitative assessment of sleep in these populations is the requirement for inpatient polysomnography (PSG), which is often not well tolerated in patients with dementia. We have recently developed a deep learning model to reliably analyze lower quality EEG data obtained from a simple, 2-lead EEG headband. This methodology allows for ambulatory assessment of sleep, with the potential for more widespread sleep staging particularly in vulnerable populations. Here we present a pilot study of ambulatory EEG sleep assessment in patients with AD and non-demented control subjects. METHODS: A total of 23 AD patient and 22 age-matched, non-demented control subjects underwent ambulatory EEG. Each subject wore the headband for up to 3 nights. A deep learning model was previously developed by our group in healthy volunteers undergoing both PSG as well as headband EEG recordings. RESULTS: AD patients were shown to have less N3 sleep than control subjects (p<0.05, t-test). No differences were found in N2 or REM sleep stages. Actigraphy supplementing the EEG will be presented. CONCLUSIONS: We show that ambulatory EEG is feasible in patients with AD. Moreover, using a deep learning model, relatively low quality, 2-lead EEG headband data can stage sleep in an ambulatory setting. Similar to studies using PSG, we find that N3 sleep is reduced in patients with AD. Our findings suggest that ambulatory EEG is a promising approach for future studies addressing sleep quality in patients with dementia.
PS10.3 Potential role of orexin receptor antagonists in the treatment of sleep disorders associated with Alzheimer’s disease
Jane Yardley¹, Jocelyn Cheng²
¹Eisai, Ltd, ²Eisai, Inc.
BACKGROUND AND AIMS: Many patients with Alzheimer’s disease (AD) display circadian rhythm and sleep-wake disturbances. Even in those at risk for AD, worse subjective sleep quality, more sleep problems, and daytime sleepiness have been associated with greater AD pathology (increased Aβ and tau). In turn, the disturbed sleep can exacerbate cognitive difficulties associated with AD. As AD progresses, the common sleep disorder is Irregular Sleep-Wake Rhythm Disorder (ISWRD), in which sleep is fragmented, and unplanned naps occur during waketime. These disturbances often lead to a decision to institutionalize. METHODS: There are no pharmacologic treatments currently approved specifically to treat the sleep disturbances associated with AD. The American Academy of Sleep Medicine (AASM) strongly recommends against the use of sedative hypnotics in these patients because of safety concerns, including increased risk of falls. To address the unmet medical need, investigations began regarding the potential use of an alternative class of sleep-promoting drugs, the dual orexin receptor antagonists (DORA), lemborexant and suvorexant, in patients with AD and ISWRD or with insomnia, respectively. RESULTS: These studies followed the findings from animal models that chronic sleep restriction accelerates Aβ plaque burden, while enhancing sleep via orexin receptor blockade markedly inhibits Aβ plaque accumulation. While few mouse AD models exhibit the sleep-wake fragmentation observed in ISWRD, lemborexant has been studied in senescence-accelerated mouse prone-8 (SAMP8) mice, which are a model for these disturbances in AD, and which display several aspects of sleep-wake and rhythm disturbances in AD, notably mistimed activity. CONCLUSIONS: In this presentation, the evidence for the role of orexin in the neuropathological changes associated with AD will be discussed, as well as the use of orexin receptor antagonists as potential therapeutic options.
PS10.4 Alterations in wakefulness and sleep quality in animal models of amyloid-beta derived neurodegeneration
Jonathan Brouillette¹, Audrey Hector¹, Chloé Provost¹, Karl Fernandes², Valérie Mongrain¹
¹CIUSSS-NIM, ²Université de Sherbrooke
Amyloid-beta oligomers (Aßo) derived from Aß1-42 peptides are the most neurotoxic species and correlate extensively with memory deficits in AD patients and animal models. Soluble Aßo begin to accumulate in the human brain approximately 10 to 15 years before any clinical symptoms of the disease and are implicated in synapse and neuronal losses at the onset of AD. Although we know that sleep perturbations are among the first clinical symptoms of AD, the specific impact of soluble Aßo on sleep features remains to be determined. Here, we performed chronic hippocampal injections of soluble Aß1-42 oligomers in rats to determine the progressive impact of amyloid pathology on sleep architecture and on the various oscillatory activities of the brain using electroencephalographic (EEG) measurements. We found that Aßo-injected rats and control rats injected with scrambled Aß spent the same amount of time in wakefulness, slow-wave sleep (SWS) and paradoxical sleep. Interestingly, Aßo increased slow-wave activity (SWA) and low-beta activity during wakefulness, and decreased theta and alpha activity during SWS. These differences were significant for the frontal cortex but not for a central recording site. Analyses are underway to determine if these changes are also observed in the transgenic 3xTg-AD mouse model, and if these alterations can be reversed by a lipid-modulating pharmacological treatment. Identifying the specific signature of Aßo on sleep features might serve as a non-invasive and cost-effective marker for the diagnosis of early AD, and as an outcome measure for new AD therapies that would be efficient before neurodegeneration causes permanent brain damage and severe memory losses.
Parallel Symposium 11: Canadian Cannabis and Psychosis Research Team (CCPRT): Multi-disciplinary investigations of the underlying neurobiology of the link between cannabis and psychosis
PS11.1 Impact of cannabis use on brain maturation in a Canadian longitudinal cohort
Jeremy Watts¹, Xavier Navarri¹, Patricia Conrod²
¹CHU Sainte-Justine/University de Montreal, ²Université de Montreal
Adolescence is a time of behavioural change, brain maturation and of increasing incidence of psychiatric illnesses. Adolescent exposure to cannabis is associated with increased risks for numerous adverse mental health outcomes including elevated risk for development of psychotic disorders. The impact of adolescent cannabis exposure on brain maturation is poorly understood. Cross-sectional studies and follow-up designs provide evidence for changes in brain structure of adolescent cannabis users but reports vary in the direction of such changes. Few studies have examined brain structure and cannabis use at more than two time points, however additional time points permit us to examine, in the same individuals, differences in brain structure in the presence of absence of a given risk factor such as cannabis use. We used a longitudinal design and participants from a population-based cohort study (n=3871) to study substance use, mental health symptoms, and brain maturation. Participants completed assessments for substance use, psychiatric symptoms for 5 years starting at age 13. Participants in the neuroimaging sub-cohort (n=150) completed structural MRI scans at three time points for each participant (at ages 13, 15, and 17). MRI images were processed using the ENIGMA consortium’s Freesurfer longitudinal neuroimaging pipeline to quantify cortical thickness and the volumes of subcortical structures. Substance use was assessed using the DEP-ADO and timeline follow-back. We applied random intercept cross-lagged panel models to investigate temporal precedence in the relationship between cannabis and changes in brain structure. This presentation will discuss preliminary analyses of this cohort examining the relationship between cannabis use and brain structure, including roles of sex and age of cannabis exposure. This talk will also discuss follow-up analyses designed to answer questions about the relevance of these findings to our understanding of the impact of cannabis exposure on mental health and brain maturation.
PS11.2 Sexually dimorphic effects of THC in adolescence: from dysregulation of dopamine guidance cues to changes in cognitive control
Giovanni Hernandez¹, Tanya Capolicchio², Katherina Estrada², Emelie Dubé², Cecilia Flores³
¹Douglas Research Institute, ²McGill University, ³Douglas Research Institute/McGill University
Cannabis is one of the most consumed substances among adolescents in North America. Its regular use during this developmental period is linked to an increased risk of cognitive impairments and psychiatric disorders later in life. However, the cellular and molecular processes underlying these effects, particularly the developing adolescent mesocorticolimbic dopamine system, remain unknown. Dopamine maturation in adolescence is mediated by the Netrin-1 guidance cue receptor, DCC, whose expression is controlled by the microRNA, miR-218. In previous research, adolescent male mice exposed to an abuse-like dose of amphetamine showed an upregulation of miR218 and a concomitant reduction of Dcc mRNA levels in the ventral tegmental area (VTA). These changes disrupt mesocorticolimbic dopamine development and cognitive control in adulthood. Here we assessed whether tetrahydrocannabinol (THC), the main psychoactive component of cannabis, alters the miR-218/DCC system in both male and female adolescent mice. Adolescent male and female C57/Bl6 mice (postnatal day 22) received intraperitoneal injections of THC, either 0, 2.5, 5, or 10 mg/kg, once every other day, for 10 days. One week after the last injection, miR-218 and Dcc mRNA expression were measured in the VTA using quantitative PCR (qPCR). In males, exposure to 5 and 10, but not 2.5 mg/kg THC, downregulated miR-218 in the VTA, inducing a concomitant increase in VTA Dcc mRNA levels. These changes are associated with improved stop impulsivity in the Go/No Go task in adulthood, similar to previous findings with a therapeutic-like dose of amphetamine. In contrast, THC did not alter miR-218 expression in females, but an increased Dcc mRNA level was observed following 5 and 10mg/kg dose. Females did not show changes in stop impulsivity in adulthood. In both males and females, THC exposure leads to dose-specific deficits in waiting impulsivity, wherein males pretreated with THC 5mg/kg show an increase in premature responses, females show similar results when pretreated with THC 2.5 mg/kg. Taken altogether, these results indicate that THC during adolescence impacts the molecular mechanisms controlling the development of mesocorticolimbic dopamine neurons in a sex-specific manner. In males, the epigenetic process by which THC mediates the netrin-1/Dcc system is via miR-218, the process for females remains to be elucidated. The effects of THC, in males cognitive control are dissociable, wherein there is an improvement in stop impulsivity but a deficit in waiting impulsivity.
PS11.3 Anxiety mediates the relationship between cannabis use frequency and psychotic-like experiences in emerging adult females
Haley Bernusky¹, Philip Tibbo¹, Fakir Yunus¹, Patricia Conrod², Matthew Keough³, Kara Thompson⁴, Marvin Krank⁵, Sherry Stewart¹
¹Dalhousie University, ²Université de Montreal, ³York University, ⁴St. Francis Xavier University, ⁵University of British Columbia Okanagan
BACKGROUND AND AIM: Cannabis is commonly used by Canadian emerging adults (18-25 years), many of whom attend post-secondary education. Frequent cannabis use has been linked with psychotic-like experiences (PLEs); the exact nature of this relationship remains unclear. Anxiety is prevalent in emerging adults and has been independently linked with both cannabis use and PLEs. Females are more susceptible to anxiety and males to both cannabis use and PLEs. We evaluated whether anxiety mediates the relationship between cannabis use frequency and PLEs in emerging adult undergraduates. We also tested for moderation of this anxiety mediational model by biological sex. We had 3 hypotheses: H1) more frequent cannabis use would be associated with more anxiety which, in turn, would be associated with greater PLEs; H2) this anxiety-mediated path would prove stronger in females; and H3) the direct path from frequent cannabis use to PLEs would be stronger in males. METHODS: A sample of 1,507 first- and second-year emerging adult university students (mean [SD] age = 19.2 [1.52] years; 67% female) were recruited. Cross-sectional, self-report survey data were collected in fall 2021 from 5 Canadian universities as part of the UniVenture study. Validated measures capturing demographics, cannabis use frequency, anxiety, and PLEs were used. RESULTS: A mediation model with cannabis use frequency as the predictor, PLEs as the outcome, and anxiety as the mediator was tested, followed by a moderated mediation model with biological sex moderating the paths from frequent cannabis use to anxiety and from frequent cannabis use to PLEs. Models were tested using the SPSS PROCESS macro with bootstrapping and 95% confidence intervals. In the first model, consistent with H1, we found evidence of a significant indirect effect of cannabis use frequency on PLEs via anxiety (a-path p < .001; b-path p < .001; 95% CI [.016, .048]); no direct effect was found (c’-path p = .946) suggesting the relationship of cannabis to PLEs is fully mediated by anxiety. In the second model, significant moderated mediation was found (95% CI [.005, .060]). More frequent cannabis use was associated with increased anxiety among females only. According to conditional indirect effects, mediation through anxiety was significant for females (95% CI [.020, .056]), but not males (95% CI [-.015, .028]), consistent with H2. No significant sex moderation was found for conditional direct effects of cannabis on PLEs: the direct effect was not significant for either males (p = .667) or females (p = .907). Thus, contrary to H3, the cannabis use frequency to PLEs path was not stronger for males than females. CONCLUSIONS: Assuming replication in prospective research, results highlight anxiety as an important intervention target in frequent cannabis users, particularly females, to potentially prevent PLEs, and in turn psychosis, in emerging adults.
Parallel Symposium 12: Arousal related brain circuits and their role in sensory processing and behaviour.
Sponsored by CERVO Brain Research Centre
PS12.1 Spatiotemporal dynamics and targeted functions of locus coeruleus norepinephrine
The locus coeruleus (LC) serves as the primary source of norepinephrine (NE) in the brain with a highly divergent set of projections to cortical and subcortical areas. The LC-NE system has been generally linked to sleep and arousal, and stress-related behaviors, in addition, at least two distinct roles have emerged with respect to learned behavior. LC activity controls action and sensory gain, and LC activity is linked with learning. Whether and how LC-NE activation facilitates these different components of learned behavior is unknown. Here, I will discuss our recent results showing that LC-NE activity displays distinct spatiotemporal dynamics to support separate functions during learned behavior. To do so, we used a behavioral task in mice with graded auditory stimulus detection and task performance. Optogenetic inactivation of the LC demonstrated that LC-NE activity was causal for both task execution and optimization. Targeted recordings of LC-NE neurons using photo-tagging, two-photon micro-endoscopy and two-photon output monitoring, showed that transient LC-NE activation preceded behavioral execution and followed reinforcement. These two components of phasic activity were heterogeneously represented in LC-NE cortical outputs, such that the behavioral response signal was higher in the motor cortex and facilitated task execution, whereas the negative reinforcement signal was widely distributed among cortical regions and improved response sensitivity on the subsequent trial. With this study, we demonstrate two concurrently encoded functions for the LC-NE system, namely task execution and performance optimization. Furthermore, we provide the first direct evidence that, at the level of LC-NE outputs, functional modularity exists and supports, at least partially, distinct aspects of learned behavior.
PS12.2 The role of hypocretin/orexin neurons in social behaviour
¹University of Calgary
Intraspecific social interactions are integral for survival and maintenance of society among all mammalian species. Yet, our understanding of the neural systems and mechanisms involved in the establishment of social connectedness and the consequences of the detrimental effects of social isolation are limited. Since their initial discovery as regulators of sleep/wakefulness and appetite in the brain, the hypocretin/orexin neurons have also been shown to play an essential role in modulating energy homeostasis, motivated and emotional behaviour. These neurons are located exclusively in the hypothalamus that regulates complex and goal-directed behaviours. The hypothalamus has previously been shown to play an important role in the modulation of social behaviour by encoding internal states. My lab investigates how the hypothalamic hypocretin/orexin neurons and their downstream circuits participate in social behaviour. We identified hypocretin/orexin neurons to exhibit a robust increase in activity in response to social interaction. We demonstrate that the activity of hypocretin/orexin neuron population is differentially encoded during interaction between familiar and stranger conspecifics. Moreover, the optogenetic inhibition of hypocretin/orexin neuron activity during social behaviour or systemic injection of hypocretin/orexin receptor antagonist prior to social behaviour leads to a reduction in the amount of time mice are engaged in social interaction. Together, these data situate the hypocretin/orexin system as the part of a larger network that plays an integral role in the modulation of social behaviour. Here, we will additionally discuss the implications of these findings in an animal model of chronic social isolation that develops long-term social impairments.
PS12.3 Interneuron contributions to state-dependent sensory processing
Katie Ferguson¹, Jenna Salameh¹, Jessica Cardin¹
BACKGROUND AND AIM: Visual information from the environment is rapidly and dynamically processed by a complex network of cortical neurons. Cortical activity patterns reflect not only changing sensory inputs, but also behavioral state (e.g., quiet wakefulness vs. active locomotion). Several lines of evidence suggest that inhibitory GABAergic interneurons (INs) may be key regulators of flexible cortical function. However, cortical GABAergic INs comprise several reciprocally connected, highly diverse subpopulations that are differentially activated during distinct states. One prominent model for state-dependent activation of cortical pyramidal neurons involves their disinhibition via arousal-activated vasoactive intestinal peptide-expressing INs (VIP-INs). These cells are hypothesized to suppress the activity of downstream INs (primarily somatostatin -expressing interneurons, or SST-INs), and consequently disinhibit pyramidal neurons. However, SST-INs are also activated by arousal, and target other IN populations. Thus, this dis-inhibitory model largely fails to account for the complex and context-dependent interactions among IN populations, leaving the role of distinct IN populations within the active cortical network largely unexplored. METHODS: We use two-photon calcium imaging in the primary visual cortex of awake behaving mice to identify cell type-specific GABAergic IN contributions to sensory processing, and to determine how behavioral state modulates the impact of GABAergic inhibition. To examine the state- and context-dependent role of IN-IN interactions, we used intersectional genetic tools to target two distinct IN populations simultaneously, focusing on the interactions between VIP-INs and its postsynaptic targets, SST-INs and pyramidal neurons. Furthermore, through both chronic and acute manipulations, we assessed the role of VIP-INs in perceptual learning using a visual detection task. RESULTS: Our data suggest a complex spatiotemporal pattern of IN-IN interactions within the local cortical circuit. We find that VIP-INs contribute to state-dependent regulation of functional connectivity and make an unanticipated contribution to SST-IN visual response properties. Our findings suggest that the unidirectional linear dis-inhibitory circuit model is not sufficient to explain the impact of VIP-IN activity on the network during visual encoding. Furthermore, we find that VIP-INs play an important role in enhancing state-dependent visual perception. CONCLUSIONS: By examining IN-IN interactions in awake behaving mice, we uncover a complex role for VIP-INs in regulating large-scale changes to sensory processing and visual perception across behavioral states.
PS12.4 Investigating the role of the claustrum in the control of behavioral state
Jesse Jackson¹, Alison Do¹, Brian Marriott¹
¹University of Alberta
The claustrum is a small hyper-connected subcortical brain region. Despite intensive investigation, the precise function of the claustrum remains unclear. Excitatory outputs of the claustrum are topographically organized, with different neurons projecting to different cortical regions. We monitored the activity of these different claustrum outputs in head-fixed mice running on a treadmill and during sleep, using fiber photometry and two-photon calcium imaging. We found that separate claustrum output pathways are differentially recruited by transitions between rest and locomotion. Using pathway specific optogenetic activation, we also found that stimulation of claustrum neurons projecting to different cortical regions produces different changes in locomotor behavior and arousal as measured by pupil diameter. Our data indicate that discrete sets of claustrum neurons may have dissociable or complimentary roles in shaping the control of behavioral state.