Subcortical connections of subdivisions of inferior temporal cortex in squirrel monkeys

Abstract

On the basis of cortical connections and architectonics, inferior temporal (IT) cortex of squirrel monkeys consists of a caudal, prestriate-recipient region, ITC; a rostral region, ITR; and possibly an intermediate region along the border of ITC and ITR, ITI (Weller & Steele, 1992). ITC contains dorsal (ITCd) and ventral (ITCv) areas. The subcortical connections of these subdivisions of IT cortex were determined in the present study from the results of cortical injections of wheat-germ agglutinin conjugated to horseradish peroxidase, [3H]-amino acids and fast blue. ITC and ITR receive afferents from the locus coeruleus, dorsal raphe, nucleus annularis, central superior nucleus, pontine reticular formation, lateral hypothalamus, paracentral nucleus, and central medial nucleus; send efferents to the superior colliculus, reticular nucleus, and striatum; and have both afferent and efferent connections with the pretectum, pulvinar, claustrum, amygdala, and basal nucleus of Meynert. ITC and ITR have different patterns of connections with a number of subcortical structures, including the pulvinar and amygdala. Injections in ITC strongly label multiple nuclei of the inferior pulvinar and the medial division of the lateral pulvinar (PLM), and moderately label the medial pulvinar (PM), whereas injections in ITR strongly label PM and moderately label PLM. Injections in ITC label sparse projections to the lateral nucleus of the amygdala, in contrast to injections in ITR that label strong projections to the lateral and basal nuclei of the amygdala. Injections in “IT” produce a pattern of subcortical label that has some features of that observed from injections in ITC and that observed from injections in ITR. Although most of the connections of ITCd and ITCv appear similar, only injections involving ITCd label the middle nucleus of the inferior pulvinar (PIM).Comparison of the subcortical connections of subdivisions of IT cortex in squirrel monkeys and what is presently known of the subcortical connections of subdivisions of IT cortex in macaque monkeys supports the previous suggestion that ITC of squirrel monkeys may be comparable to area TEO of macaques, IT, may be comparable to posterior area TE, and ITR may be comparable to anterior area TE (Weller & Steele, 1992).

Visual habit formation in monkeys with neurotoxic lesions of the ventrocaudal neostriatum

“…43 for evidence that this version of the concurrent visual-discrimination task, like the 24-h ITI version, is insensitive to the effects of medial temporal damage). Taken together with the anatomical connectional evidence (9)(10)(11)(12)(13)(33)(34)(35)(36), these several different patterns of lesion-induced deficit support the proposal (29,30) that long-term visual learning and memory are mediated by at least two parallel pathways diverging from a common source, with a TE-limbic projection forming part of a neural circuit critical for visual recognition and a TE-neostriatal projection comprising part of a circuit mediating visual habit formation. (As indicated at the outset, a third projection from TE to the inferior prefrontal convexity seems to be part of yet another circuit, this one serving short-term visual memory.…”

Pulvinar contributions to the dorsal and ventral streams of visual processing in primates

“…Similar results were reported by Bazier, et al (1993) and Webster et al (1993), with some additional involvement of PIcl with TEO injections. In squirrel monkeys, injections in a caudal IT region, ITc (comparable to TEO), labeled neurons in PLvl and PIcl, but also in PIp (Steele and Weller, 1993). The neurons labeled in PIp may have resulted from the injection also involving rostral IT, where injections labeled PIp, PLdm, and PM.…”

“…Subsequent studies led to some modification of the border of DL, and to the subdivision of DL into rostral and caudal areas, DLr and DLc, containing parallel retinotopic representations and differing in connection patterns (Cusick and Kaas, 1988;Steele and Weller, 1993). The rostral area, DLr has cortical connections that associate it with the dorsal stream while the caudal division has connections predominantly with the ventral stream.…”

Differential Activation of the Caudate Nucleus in Primates Performing Spatial and Nonspatial Working Memory Tasks

“…Previous studies have shown that the posterior part of the caudate nucleus and the posteroventral putamen participate in VD and object discrimination tasks (Battig et al, 1960;Divac et al, 1967;Buerger et al, 1974). These striatal regions receive projections from the inferotemporal cortex (Saint-Cyr et al, 1990;Steele and Weller, 1993;Webster et al, 1993;Yeterian and Pandya, 1995), further suggesting that they are parts of a network involved in visual associative memory. The absence of increase in the tail during the VD task may be explained by the fact that neurons responding to physical patterns of visual stimuli in the tail rapidly habituate and may not respond after several (one to eight) presentations of the same stimuli (Caan et al, 1984).…”