UNTANGLING THE CONTRIBUTION OF BASOLATERAL AMYGDALA CELL SUBPOPULATIONS TO MIXED EMOTIONAL MEMORY ENGRAM

How do we categorise experiences? Why does one remember the same event in a different light than another? Those questions relate to the brain’s computation of the emotional values of experiences, positive or negative, which allows us to make decisions, by remembering the outcome of past choices. The basolateral amygdala (BLA) is a hub region for emotional memory. In particular, some BLA neurons respond preferentially to either positive or negative events. However, there is no consensus about how these cells are recruited. Analysis of their topographic organisation and molecular characterisation in mice has revealed two spatially and genetically separate populations with opposite activity. Contrastingly, other studies suggest that they are intermingled. The latter would be consistent with the idea that engram recruitment is governed by excitability and stochastics. We hypothesize that this apparent contradiction may be explained by the fact that experiences traditionally considered absolutely aversive or rewarding may, in reality, comprise several emotional components. We use the temporally precise activity-dependent optogenetics tool f-FLiCRE to target the neurons active at different time points of a mixed emotional experience. We analyse their topographical distribution within the BLA and their role in behavior by stimulating those tagged neurons during memory recall. Thereby we aim to disentangle sub-engrams in the BLA, encoding relatively negative or positive valences, as parts of the engram network of the memory of a single experience.