Corticocortical connections of visual, sensorimotor, and multimodal processing areas in the parietal lobe of the macaque monkey

We studied the corticocortical connections of architectonically defined are as of parietal and temporoparietal cortex, with emphasis on areas in the in traparietal sulcus (IPS) that are implicated in visual and somatosensory in tegration. Retrograde tracers were injected into selected areas of the IPS, superior temporal sulcus, and parietal lobule. The distribution of labeled cells was charted in relation to architectonically defined borders through out the hemisphere and displayed on computer-generated three-dimensional re constructions and on cortical flat maps. Injections centered in the ventral intraparietal area (VIP) revealed a complex pattern of inputs from numerou s visual, somatosensory, motor, and polysensory areas, and from presumed ve stibular- and auditory-related areas. Sensorimotor projections were predomi nantly from the upper body representations of at least six somatotopically organized areas. In contrast, injections centered in the neighboring ventra l lateral intraparietal area (LIPv) revealed inputs mainly from extrastriat e visual areas, consistent with previous studies. The pattern of inputs to LIPv largely overlapped those to zone MSTdp, a newly described subdivision of the medial superior temporal area. These results, in conjunction with th ose from injections into other parietal areas (7a, 7b, and anterior intrapa rietal area), support the fine-grained architectonic partitioning of cortic al areas described in the preceding study. They also support and extend pre vious evidence for multiple distributed networks that are implicated in mul timodal integration, especially with regard to area VIP. (C) 2000 Wiley-Lis s, Inc.