SUBCORTICAL CONNECTIONS OF SUBDIVISIONS OF INFERIOR TEMPORAL CORTEX IN SQUIRREL-MONKEYS

On the basis of cortical connections and architectonics, inferior temp oral (IT) cortex of squirrel monkeys consists of a caudal, prestriate- recipient region, IT(C); a rostral region, IT(R); and possibly an inte rmediate region along the border of IT(C) and IT(R), ''IT(I)'' (Weller & Steele, 1992). IT(C) contains dorsal (ITCd) and ventral (ITCv) area s. The subcortical connections of these subdivisions of IT cortex were determined in the present study from the results of cortical injectio ns of wheat-germ agglutinin conjugated to horseradish peroxidase, [H-3 ]-amino acids and fast blue. IT(C) and IT(R) receive afferents from th e locus coeruleus, dorsal raphe, nucleus annularis, central superior n ucleus, pontine reticular formation, lateral hypothalamus, paracentral nucleus, and central medial nucleus; send efferents to the superior c olliculus, reticular nucleus, and striatum; and have both afferent and efferent connections with the pretectum, pulvinar, claustrum, amygdal a, and basal nucleus of Meynert. IT(C) and IT(R) have different patter ns of connections with a number of subcortical structures, including t he pulvinar and amygdala. Injections in IT(C) strongly label multiple nuclei of the inferior pulvinar and the medial division of the lateral pulvinar (PL(M)), and moderately label the medial pulvinar (PM), wher eas injections in IT(R) strongly label PM and moderately label PL(M). Injections in IT(C) label sparse projections to the lateral nucleus of the amygdala, in contrast to injections in IT(R) that label strong pr ojections to the lateral and basal nuclei of the amygdala. Injections in ''IT(I)'' produce a pattern of subcortical label that has some feat ures of that observed from injections in IT(C) and that observed from injections in IT(R). Although most of the connections of ITCd and ITCv appear similar, only injections involving ITCd label the middle nucle us of the inferior pulvinar (Pl(M)). Comparison of the subcortical con nections of subdivisions of IT cortex in squirrel monkeys and what is presently known of the subcortical connections of subdivisions of IT c ortex in macaque monkeys supports the previous suggestion that IT(C) o f squirrel monkeys may be comparable to area TEO of macaques, IT(I) ma y be comparable to posterior area TE, and IT(R) May be comparable to a nterior area TE (Weller & Steele, 1992).