PROJECTIONS OF THE LATERAL ENTORHINAL CORTEX TO THE AMYGDALA - A PHASEOLUS-VULGARIS-LEUKOAGGLUTININ STUDY IN THE RAT

In addition to providing a gateway to the hippocampus, the entorhinal cortex has significant projections to the amygdala. In the present inv estigation, the organization of the projections of the lateral entorhi nal cortex to the amygdala was studied in the rat using the sensitive anterograde tracer Phaseolus vulgaris leucoagglutinin. Each of the thr ee main subdivisions of the lateral entorhinal cortex provided a chara cteristic projection to the amygdala that mainly arose from the deep c ortical layers. The projections from the dorsolateral and ventrolatera l entorhinal areas were much stronger than those arising from the vent romedial entorhinal area. The primary targets of the dorsolateral and ventrolateral entorhinal areas were the basolateral amygdala, lateral capsular subdivision of the central nucleus and caudal portions of the cortical nuclear complex. The dorsolateral entorhinal area projects m ainly to the lateral part of the basal nucleus, while the ventrolatera l entorhinal area projects mainly to its medial part. A transitional r egion al the rostral pole of the ventrolateral entorhinal cortex has a dditional strong projections to the lateral subdivision of the central nucleus, medial amygdaloid nucleus and the intra-amygdaloid portion o f the bed nucleus of the stria terminalis. The results of the present study indicate that the amygdala is one of the principal targets of th e entorhinal cortex. The correspondence between the topography of ento rhino-hippocampal connections and entorhino-amygdaloid connections sug gests that the amygdaloid projection arising in each of the three main subdivisions of the entorhinal cortex conveys information processed i n different septotemporal portions of the hippocampal formation. These entorhinal projections, which probably convey complex relational (inc luding contextual) information to the amygdala, are in a position to p roduce different behavioral responses by activating different portions of the amygdaloid nuclear complex. (C) 1997 IBRO.