CA4
Region CA4 (often called the hilus or hilar region when considered part of the dentate gyrus, as neurons here do not have pyramidal morphology like those of areas CA1 & CA3 (suggested by Lorente de Nó and verified by David G. Amaral)) contains mossy cells that primarily receive inputs from granule cells located nearby in the dentate gyrus in the form of mossy fibers. They also receive a small number of connections from pyramidal cells located in CA3. They, in turn, project back into the dentate gyrus at distant septotemporal levels.