Dr. Jung Hoon Jung, Hospital for Sick Children, University of Toronto
Scientific publication
Jung JH, Wang Y, Mocle A J, Zhang T, Köhler S, Frankland P. W, Josselyn S. A. Examining the engram encoding specificity hypothesis in mice. Neuron 111(11): 1830-1845. (20230607)
Study of memory recall reveals biological basis of encoding specificity in the brain
In humans, psychology research has shown that memory retrieval, the process of accessing previously stored information, depends on retrieval conditions. Memory is best recalled by retrieval cues that overlap with training cues. This is called the encoding specificity hypothesis (first articulated by Canadian cognitive neuroscientist, Endel Tulving) and is also observed in other animals.
Memories are encoded by “engram” neurons, which are specific and sparse groups of neurons that store and participate in the memory encoding process. To test the encoding specificity hypothesis, Jung Hoon Jung and colleagues investigated the activation and reactivation of neurons in the engram ensemble mediated by different ways of changing the encoding versus retrieval conditions (both with pharmacological/internal cues and external retrieval cues).
In this study, researchers applied three different engram visualization systems to verify whether recall cues that closely overlap with training cues mediate strong memory retrieval via high engram reactivation. They found that maximal engram reactivation (same learning-involved neurons activating at memory recall) and memory recall occur when retrieval conditions closely matched training conditions. These findings provide a biological basis for the encoding specificity hypothesis and highlight that memory recall involves an interaction between stored information (engram) and information available at retrieval (the memory retrieval cue).
Insights into the basic mechanisms of how neuronal activity codes for a memory trace may provide core knowledge crucial to the development of next-generation treatments in human conditions associated with a breakdown in the optimal structuring of information in various neurological disorders, such as autism spectrum disorder, post-traumatic stress disorder, and Alzheimer’s disease. These neuronal disorders show abnormal memory processes during acquisition, storage, generalization, and even memory extinction. In addition to better understanding the mechanisms behind memory and learning, these findings contribute to our understanding of how to overcome memory and learning abnormalities in various neurological disorders in humans. Only by understanding how the brain functions in normal circumstances can we hope to understand how to fix it when dysfunction occurs.
About Dr. Jung Hoon Jung
Dr. Jung Hoon Jung performed this research as a post-doctoral fellow in the Sheena Josselyn / Paul Frankland laboratory at the Hospital for Sick Children in Toronto, in collaboration with Stefan Kohler’s lab at the University of Western Ontario. Jung Hoon Jung is a neurobiologist specializing in investigating molecular and circuit mechanisms underlying memory in normal and pathological conditions.
His academic training and research experience have provided him with an excellent background in multiple biological disciplines including molecular neuroscience, electrophysiology, behavioral science, genetics, and optogenetics. His goal is to become a principal investigator leading a laboratory to investigate psychiatric disorders and his training and strong publication record has provided him with a strong foundation to accomplish this goal.
Sources of funding
This work was supported by grants from the National Research Foundation (NRF) of Republic of Korea funded by the Ministry of Education, the National Institute of Mental Health (NIMH), the Brain Canada Foundation, the Canadian institutes of Health Research and the Natural Sciences and Engineering Research Council of Canada.
