Topographic projections from the periamygdaloid cortex to select subregions of the lateral nucleus of the amygdala in the rat

Information from most of the sensory modalities enters the amygdala via the lateral nucleus. The olfactory information, however, arrives at the amygdala through the superficial nuclei, including the periamygdaloid cortex. To find out whether the olfactory information can modulate the processing of sensory information in the lateral nucleus we injected Phaseolus vulgaris leucoagglutinin, an anterograde axonal tracer, into the different divisions of the periamygdaloid cortex. We found that the PAC division of the periamygdaloid cortex projects to the ventrolateral and medial divisions, but not the dorsolateral division, of the lateral amygdaloid nucleus. Therefore, the projection from the PAC to the lateral nucleus provides a route, by which the olfactory information may become associated with other sensory modalities. Also, together with our previous finding that the lateral nucleus projects to the periamygdaloid cortex, the present data demonstrate that the lateral nucleus and the PAC are reciprocally connected.