INTRINSIC CONNECTIONS OF THE RAT AMYGDALOID COMPLEX - PROJECTIONS ORIGINATING IN THE LATERAL NUCLEUS

The amygdaloid complex receives sensory information from a variety of sources. A widely held view is that the amygdaloid complex utilizes th is information to orchestrate appropriate species-specific behaviors t o ongoing experiences. Relatively little is known, however, about the circuitry through which information is processed within the amygdaloid complex. The lateral nucleus is the major recipient of extrinsic sens ory information and is the origin of many intra-amygdaloid projections . In this study, we reinvestigated the organization of intra-amygdaloi d projections originating from the lateral nucleus using the anterogra de tracer Phaseolus vulgaris leucoagglutinin (PHA-L). The lateral nucl eus has highly organized intranuclear connections. Dense projections i nterconnect rostral and caudal levels of the lateral and the medial di visions of the nucleus, and the lateral and medial divisions of the la teral nucleus are also interconnected. The major extranuclear projecti ons of the lateral nucleus are (in descending order of magnitude) to t he accessory basal nucleus, the basal nucleus, the periamygdaloid cort ex, the dorsal portion of the central division of the medial nucleus, the posterior cortical nucleus, the capsular division of the central n ucleus, and the lateral division of the amygdalohippocampal area, The pattern of extranuclear projections varied depending on the rostrocaud al or mediolateral location of the injection site within the lateral n ucleus. These findings indicate that intra-amygdaloid projections orig inating in the lateral nucleus are both more widespread and more topog raphically organized than was previously appreciated. (C) 1995 Wiley-L iss, Inc.