SUBICULAR CORTEX OF THE CAT - ANATOMICAL AND ELECTRO-PHYSIOLOGICAL STUDY

The anatomic organization of the hippocampal formation in the cat was studied by means of (a) horseradish peroxidase histochemistry, (b) [3H]leucine radioautography, and (c) electrophysiological identification of antidromically activated single units. The data indicate that the CA1 field, prosubiculum, and adjacent subiculum are the source of origin of fibers terminating in the caudal septum. The subiculum and adjacent presubiculum are the only sources of hippocampal efferent fibers which project to the medial mammillary nucleus. The cells of the presubiculum and retrosplenial cortex give rise to the axons which project to the anterior thalamus. Efferent fibers project through the fornix and are topographically distributed to the mammillary bodies and septal area. Specifically, axons arising near the septal pole of the hippocampal formation project to the dorsal aspect of the medial mammillary nucleus or the dorsomedial part the lateral septal nucleus. Axons arising from cells situated progressively more proximal to the temporal pole of the hippocampal formation project to progressively more ventral levels of the medial mammillary nucleus or more lateral parts of the lateral septal nucleus. It was also noted that subicular fibers have slow conduction velocities and that evidence of possible axonal branching of fornix fibers was not obtained. © 1979.