DEVELOPMENT OF INTRINSIC HIPPOCAMPAL DYNAMICS IN HEALTH AND DISEASE

Cognitive functions like memory and navigation rely on the ability of the hippocampus to generate neural representations of behaviorally relevant variables and events in the form of discrete cell assemblies that activate in a sequential manner. In the adult brain, hippocampal cell assembly sequences arise from intrinsic neuronal dynamics embedded in local circuits onto which extrinsic multi-sensory input is mapped. In contrast, in early developmental stages, hippocampal dynamics are significantly driven by bottom-up extrinsic input (Leprince et al., 2023). Interestingly, during the second postnatal week, the rise of somatic inhibition transitorily disengages neuronal dynamics from extrinsic input in the CA1 region of the mouse hippocampus (Dard et al., 2022). We hypothesize that the development of inhibitory neurons initiates intrinsic circuit dynamics, thus inaugurating a critical window in hippocampal function. Using a combination of genetic strategies and in vivo calcium imaging, we aim to test whether the rise of PV+ or CCK+ interneurons, the two main sources of somatic inhibition in the CA1 region, triggers the development of intrinsic dynamics in hippocampal circuits in health and disease.