High-speed connections

Armen Saghatelyan

Armen Saghatelyan

Researchers find a mechanism that allows the brain to reconfigure connections between neurons in mere minutes.

A team from the Quebec Mental Health Institute – Université Laval has discovered a mechanism that allows the brain to rapidly reconfigure connections between its neurons. According to the researchers, whose findings were published in a recent issue of the journal Nature Communications, this mechanism plays a central role in brain plasticity.

The mechanism affects key structures called dendritic spines, which are microscopic protuberances found on dendrites. If neurons were trees, dendrites would be branches and dendritic spines would be twigs. Like dendrites, dendritic spines make connections with neighboring neurons. “However, they are 100 to 1000 times more abundant than dendrites. They therefore play a very important role in neuronal connections in the brain,” says Armen Saghatelyan, who led the study published in Nature Communications.

The number of connections offered by dendritic spines peaks during embryogenesis and in early life, a period scientists call a critical phase of brain development. “Environmental stimuli cause some of these connections to stabilize, while others disappear. Once the critical period of development is over, formation of new dendritic spines is greatly reduced in the brain, “says Professor Saghatelyan.

The researcher and his team have now shown that the connections made by dendritic spines are not static. Indeed, applying an electrophysiological stimulation to a neuron located near a dendritic spine can cause the spine to detach from the neurons to which it was connected and to form a new connection with the neuron that has been stimulated. “The stimulated neuron releases two factors – glutamate and BDNF – which are detected by a kind of antenna, called filopodium, found on the dendritic spine, explains the researcher. Both factors induce mobility and directional movement of dendritic spine towards the stimulated neuron. ”

This reconfiguration of the connections can occur, for example, when a mouse is exposed to a smell, researchers have shown. “We observed that new connections were formed in 10 to 15 minutes. This is fast considering that the formation of a new spine requires several hours or even days. So this is a mechanism that allows rapid reorganization of neuronal networks in response to sensory stimulation. ”

In addition to its fundamental value, this discovery suggests applications long confined to science fiction. Indeed, some mental health problems such as autism spectrum disorders and fragile X syndrome, as well as neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases are associated with an alteration of dendritic spines and the connections they establish. “The mechanism we have discovered opens up the possibility of modifying neural connections by stimulating target neurons. This is not for tomorrow, insists Armen Saghatelyan, but techniques of optogenetics, which allow the stimulation of specific neurons using light, already exist. ”

Other authors of the article published in Nature Communications are Vincent Breton Provencher, Karen Bakhshetyan, Delphine Hardy, Rodrigo Bammann, Marina Snapyan and Daniel Côté, Université Laval, and Francesco Cavarretta and Michele Migliore, Yale University.

Source of text: Le Fil – Université Laval

Translation: CAN-ACN

Original research article:

Breton-Provencher V, Bakhshetyan K, Hardy D, Bammann RR, Cavarretta F, Snapyan M, Côté D, Migliore M, Saghatelyan A. Principal cell activity induces spine relocation of adult-born interneurons in the olfactory bulb. Nat Commun. 2016 Aug 31;7:12659. doi: 10.1038/ncomms12659.