How memories are formed and encoded in the brain network?

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A few months ago, a new neuroscientist professor was appointed at ESPCI Paris to strengthen the Brain Plasticity Unit: Gisella Vetere. After a PhD in Italy and a postdoc in Toronto where she worked on memory consolidation in mice, she decided to join the school.

“Students here at ESPCI are very competitive and I am eager to teach them how the brain works and how new techniques, combining engineering, optics and physics knowledge are changing the way neuroscientists today learn about the brain”. In her new team C4 (Cerebral Codes and Circuits Connectivity) she will use cutting-edge techniques such as optogenetics, chemogenetics, graph theory analysis of whole-brain networks and in vivo imaging using miniaturized microscope to discover how the mouse brain encode, process and store external information.
In a previous paper she found that the neural substrate of fear memory is based on distributed network interactions and that regions of the brain highly connected with the rest of the brain are needed to remember (Vetere et al, 2017, Neuron).

The C4 team is interested in understanding how memories are recalled later in time. The recall of a memory is supported by the coordinated activity of a distributed network of brain regions. GV found that some of the “nodes” of the network play a more important role in the recall of the memory if they are strongly connected with the rest of the network.

In these days, her last work from the Sick Kids Hospital in Toronto has been published in the prestigious journal Nature Neuroscience. Here, Gisella and her colleagues replaced external stimuli (i.e. an odor, a fear or reward experience) with the optogenetic stimulation of its corresponding pattern of neuronal activity, inducing the formation of a memory of an event never experienced before. This was the first demonstration that, simply knowing the patterns of activity generated by distinct external representations, we can reverse engineer a memory by artificially creating these patterns of activity in the absence of a sensory experience.
She implanted an artificial odor memory that was neurally and behaviourally comparable to a real one: both real and implanted memories were overlapping brain circuits.

To implant an artificial memory in the brain in absence of external experiences, GV and colleagues used the olfactory system (in the picture are showed the olfactory bulbs of a mouse) where specific glomeruli (in green in the picture) are know to respond to specific odors. The use of optogenetics allowed the researchers to artificially activate them without the presentation of the real odor.

Associated publications:

Vetere et al., Chemogenetic Interrogation of a Brain-wide Fear Memory Network in Mice, Neuron, 2017
Vetere et al., Memory formation in the absence of experience, Nature Neuroscience, 2019.


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