Abatis, M., Perin, R., Niu, R., van den Burg, E., Hegoburu, C., Kim, R., … & Stoop, R. (2024). Fear learning induces synaptic potentiation between engram neurons in the rat lateral amygdala. Nature Neuroscience, 27(7), 1309-1317. https://www.nature.com/articles/s41593-024-01676-6
Ex vivo simultaneous 12 cell patch clamping
Rat Lateral Amygdala
Previous experiments have shown that the strengthening of excitatory synapses from sensory areas onto Lateral Amygdala (LA) pyramidal neurons provides the specificity of a fear memory (e.g. Nabavi 2014). In this paper, Abatis et al. show how the strengthening of recurrent excitatory synapses among specific LA pyramidal neurons form an autoassociative attractor network which amplifies these inputs sufficiently to trigger the fear response. In their key experiment, they virally label LA engram cells which activated during the recall of a contextual fear memory. They subsequently performed ex vivo 12 cell patch clamp on these engram (and non-engram) cells to test their functional interconnectivity. They find a higher number of synaptic connections, and stronger synaptic connections, among engram cells. This result, combined with their electrophysiological analysis of baseline excitability, suggests that this strengthening of synaptic connectivity forms an autoassociative attractor network underlying the particular fear memory. The implication is that each LA memory is associated with such an attractor network.
“Fear conditioning specifically causes potentiation of synaptic connections between learning-recruited neurons. These findings of synaptic plasticity in an autoassociative excitatory network of the LA may suggest a basic principle through which a small number of pyramidal neurons could encode a large number of memories.”
