Abstract
The fasciola cinereum (FC) is a small subregion of the hippocampus that has been relatively unattended and less known compared with other subregions with respect to anatomical characteristics and functional significance. The lack of a detailed anatomical characterization of the FC has created ambiguity in the literature regarding the definition of FC borders with the CA1 subregion and attribution of cognitive functions to specific subregions of the hippocampus. Here, we show that the anatomical borders of the FC can be clearly defined histologically, and the region itself is characterized by unique anatomical connections and physiological properties. The major output of the FC is to the dentate gyrus (DG) and the FC itself. Firing properties of cells recorded from the FC were different from those in the CA1, and no sign of neurogenesis was detected in the FC. Selective ablation of neurons in the FC, successfully accomplished using colchicine, significantly impaired acquisition of novel visual-contextual memory in rats, without affecting retrieval of familiar visual-contextual memories. Our findings suggest that, given its connections to the DG, the FC may play critical roles in learning novel contextual behavior.
