Figure 1. Schematic of experimental question.

a.) Perisomatically-targeting CCK positive basket cells (CCKBCs) selectively target non-perforant path forming calbindin positive (calb⁺) principal cells while largely avoiding ipsilaterally-projecting reelin positive (reelin⁺) principal cells that form the perforant path (DG= dentate gyrus). We investigate in this study whether PV containing basket cells (PVBCs) select their targets with respect to long-range projection pattern. b) Since PVBCs do contact both types of principal cell (Varga et al., 2010), it is possible that individual PVBCs are either simultaneously contacting both calb⁺ and reelin⁺ principal cells (top), or that there are two subpopulations of PVBCs that are each selective for one principal cell type (bottom). c) This image was reproduced with permission from Varga et al., 2010 Nature Neuroscience, and demonstrates that CCK-immunopositive axon terminals (left panel) selectively surround the somata of some (asterisks) but not all (triangles) principal cells in MEC_layerII (principal cells were visualized by GluR2/3 immunopositivity; middle panel). In contrast, axons from PVBCs (right panel) surround the perisomatic region of most principal cells. Scale bar in c = 10μm.