Mapping PV+ interneuron connectivity in CA1: Unraveling the inhibitory architecture of hippocampus

While excitatory pyramidal cells are well-studied in hippocampal spatial coding and memory, the inhibitory circuits, particularly Parvalbumin-positive (PV+) interneurons, are underexplored despite their role in coordinating gamma oscillations crucial for memory processes. The detailed anatomical organization of PV+ axonal projections remains unclear, limiting our understanding of hippocampal computation. This study aims to map PV+ interneuron processes in the CA1 region using synchrotron X-ray imaging and APEX-PV+ labeling. It will explore (1) the extent of PV+ innervation across CA1, (2) synaptic targeting patterns on pyramidal neuron somas, and (3) how PV+ connectivity influences network-level inhibition. This will illuminate both direct inhibition and disinhibition mechanisms, bridging structural connectivity and functional dynamics, and informing future computational models of hippocampal circuits.