Perirhinal cortex area 35 controls the functional link between the perirhinal and entorhinal‐hippocampal circuitry

In several experimental conditions, neuronal excitation at the perirhinal cortex (PC) does not propagate to the entorhinal cortex (EC) due to a “wall” of inhibition, which may help to create functional coupling and un‐coupling of the PC and EC in the medial temporal lobe. However, little is known regarding the coupling control process. Herein, we propose that the deep layer of area 35 in the PC plays a pivotal role in opening the gate for coupling, thus allowing the activity in the PC to propagate to the EC. Using voltage‐sensitive dye imaging for the brain slices of rodents, we show that a slowly inactivating potassium conductance in this area is essential to induce excitation overtaking the inhibitory control. This coupling between the distinct neural circuits persists for at least 1 h. We elucidate further implications of this network‐level plastic behavior and its mechanism. Our brains gate the pathways to the hippocampal memory system during episodic memory processing. Our work, using optical imaging of rodent brain slices, has revealed a neural mechanism for the gating action in a subregion of the perirhinal cortex. We discuss the implications of this finding and the novel gating mechanism.