PROJECTIONS OF THE MEDIAL AND LATERAL PREFRONTAL CORTICES TO THE AMYGDALA - A PHASEOLUS-VULGARIS-LEUKOAGGLUTININ STUDY IN THE RAT

The projections of different subfields of the medial and lateral prefr ontal cortices to the amygdala were studied in the rat using the sensi tive Phaseolus vulgaris leucoagglutinin anterograde tract tracing tech nique. Injections into the infralimbic cortex produced anterograde lab eling in the lateral capsular subdivision of the central nucleus, supe rficial (corticomedial) amygdaloid nuclei, lateral and accessory basal nuclei, and the anterior amygdaloid area. Injections into the caudal portion of the infralimbic cortex produced additional labeling in the intermediate subdivision of the central nucleus. The prelimbic cortex had projections to the medial portion of the magnocellular basal nucle us and adjacent portions of the lateral nucleus and lateral capsular s ubdivision of the central nucleus. The medial precentral cortex had pr ojections to the rostromedial part of the magnocellular basal nucleus and adjacent portions of the lateral capsular subdivision of the centr al nucleus. Injections into the lateral orbital and ventral agranular insular cortices produced labeled fibers in the rostral part of the su perficial amygdala, lateral capsular subdivision of the central nucleu s, and the lateral and accessory basal nuclei. The dorsal agranular in sular area had projections to several different subdivisions of the ce ntral nucleus as well as to the rostrolateral magnocellular basal nucl eus; the latter projections were complementary to those originating in the prelimbic area. The present study indicates that each portion of the prefrontal cortex has a distinctive projection to the amygdala. Th e ventral areas of the lateral and medial prefrontal cortices, which r eceive olfactory projections, are the only prefrontal cortical areas w ith projections to the olfactory-related superficial amygdaloid nuclei . The more dorsally situated prefrontal areas, the dorsal agranular in sular area and prelimbic cortex, have complementary projections to the basal nucleus, suggesting that they modulate separate prefrontal cort ico-striatal-pallidal circuits. The specificity of prefrontal cortico- amygdaloid projections is indicative of their involvement in discrete functions.