Connections of inferior temporal areas TE and TEO with medial temporal-lobe structures in infant and adult monkeys

Abstract

As part of a long-term study designed to examine the onageny of visual memory in monkeys and its underlying neuralcircuitry, we have examined the connections between inferior temporal cortex and medial temporal-lobe structures in infant and adult monkeys. Inferior temporal cortical areas TEO and TE were injected with WGA conjugated to HRP and Mated amino acids, respectively, or vice versa, in 1-week-old and 3-4-yr-old Macaca mulatta, and the distributions of tabbed cells and terminals were examined in both limbic ikuctures and temporal-lobe cortical areas. In adult monkeys, inferior temporal-limbic connections included projections from area TEO to the dorsal portion of the lateral nucleus of the amygdala and from area TE to the lateral and lateral basal nuclei; inputs to both areas TEO and TE included those from the lateral, lateral basal, and medial basal nuclei of the amygdala and to area TE from the accessory basal nucleus. Additional limbic inputs to both areas TEO and TE arose from the posterior portion of the presubiculum. In infant monkeys, we found, in addition to these adultlike connections, a projection from area TEO to the lateral basal nucleus of the amygdala. Inferior temporal cortical connections in adult monkeys included projections from area TEO tearea TE and, in turn, from area TE to area TG and perirhinal area 36, as well as from area TE back to area TEO; inputs to both areas TEO and TE included those from area TG, penrhinal areas 35 and 36, and parahippocampal areas TF and TH. All of these adultlike connections were also ob- served in infant monkeys, but, in addition, the infants showed Ejections from area TE to perirhinal area 35 as well as to parahippocampal areas TF and TH, and from area TEO to area TF. Moreover, in infants, the projection from area TE to pwminal area 36 was considerably more widespread than in adults, both in areal extent and in laminar distribution. The results therefore indicate the existence of projections in intent monkeys from inferior temporal areas to the amygdala, Periminal cortex, and parahippocampal cortex that are either eliminated in adults or more refined in their distribution. Both elimination and refinement of projections thus appear to characterize the maturation of axonal pathways between the inferior temporal cortex and medial temporal-lobe structures in monkeys.