The fasciola cinereum subregion of the hippocampus is important for the acquisition of visual contextual memory

Summary The fasciola cinereum (FC) is a subregion of the hippocampus that has received relatively little research attention compared with other hippocampal subregions with respect to anatomical characteristics and functional significance. Here, we show that the FC exhibits clear anatomical borders with CA1. The FC consists of granule cells, but adult neurogenesis was not found. The FC receives inputs from the lateral entorhinal cortex and perirhinal cortex while projecting to the crest of the dentate gyrus (DG). Neurotoxic lesioning of the FC using colchicine impaired the acquisition, but not retrieval, of visual contextual memory in rats. FC lesions also impaired place recognition and object-in-place memory. Place cells in the FC showed robust place fields but fired only transiently in their fields compared with those in CA1. Our findings suggest that the FC may play critical roles in learning a novel environment by facilitating pattern separation in the DG of the hippocampus.