CORTICAL CONNECTIONS OF AREAS V3 AND VP OF MACAQUE MONKEY EXTRASTRIATE VISUAL-CORTEX

The cortical connections of visual area 3 (V3) and the ventral posteri or area (VP) in the macaque monkey were studied by using combinations of retrograde and anterograde tracers. Tracer injections were made int o V3 or VP following electrophysiological recording in and near the ta rget area. The pattern of ipsilateral cortical connections was analyze d in relation to the pattern of interhemispheric connections identifie d after transection of the corpus callosum. Both V3 and VP have major connections with areas V2, V3A, posterior intraparietal area (PIP), V4 , middle temporal area (MT), medial superior temporal area (dorsal) (M STd), and ventral intraparietal area (VIP). Their connections differ i n several respects. Specifically, V3 has connections with areas V1 and V4 transitional area (V4t) that are absent for VP; VP has connections with areas ventral occipitotemporal area (VOT), dorsal prelunate area (DP), and visually responsive portion of temporal visual area F (VTF) that are absent or occur only rarely for V3. The laminar pattern of l abeled terminals and retrogradely labeled cell bodies allowed assessme nt of the hierarchical relationships between areas V3 and VP and their various targets. Areas V1 and V2 are at a lower hierarchical level th an V3 and VP; all of the remaining areas are at a higher level. V3 rec eives major inputs from layer 4B of V1, suggesting an association with the magnocellular-dominated processing stream and a role in routing m agnocellular-dominated information along pathways leading to both pari etal and temporal lobes. The convergence and divergence of pathways in volving V3 and VP underscores the distributed nature of hierarchical p rocessing in the visual system. (C) 1997 Wiley-Liss, Inc.