SPATIAL CORTICAL PATTERNS OF METABOLIC-ACTIVITY IN MONKEYS PERFORMINGA VISUALLY GUIDED REACHING TASK WITH ONE FORELIMB

The 2-[C-14]deoxyglucose method was used to map the metabolic activity in the neocortex of monkeys (Macaca nemestrina) performing a visually guided reaching task with one forelimb. Monkeys received liquid rewar d for correct; single directional reaching movements, which were requi red at a rate of about 10 per minute. We estimated the weighted averag e of local glucose consumption within several neocortical areas, and w e reconstructed quantitative, high-resolution, two-dimensional maps of the detailed spatiointensive patterns of activity. Our findings demon strate the involvement of the striate and prestriate cortices, the inf erior intraparietal and superior temporal visual association areas, th e frontal eye field and the caudal periprincipal cortex, the primary s omatosensory and the related superior intraparietal area, the primary and association auditory cortices, the superior temporal multimodal re gion, and the premotor, primary, supplementary, and cingulate motor ar eas. The visual cortex in the superior temporal and the intraparietal sulci, which is concerned with ''where'', was activated during visuall y guided reaching. In contrast, the inferior temporal visual associati on cortex, which is concerned with ''what'', was not involved in our s tudy. We suggest that the activated direction-selective layer four of V1 and the thick stripes of V2 convey visuomotor information to the ac tivated cortex in the posterior bank and the floor of the superior tem poral sulcus, which may encode the constantly updated position of the moving forelimb. In parallel, the activated cortex in the ventral part and the lateral bank of the intraparietal sulcus may encode visuospat ial information related to the localization of the Visual target in th e extrapersonal space. Furthermore, the dorsal part of the medial bank of the intraparietal sulcus may be involved in proprioceptive guidanc e of movement, based on the parallel metabolic effects shown only cont ralateral to the moving forelimb within this region and the forelimb r epresentations in the primary somatosensory and motor cortices. Finall y, the bilaterally activated network including the inferior postarcuat e skeletomotor and prearcuate oculomotor cortical fields and the cauda l periprincipal region 46 may participate in sensory and oculomotor to motor transformations, in parallel with the medial and lateral intrap arietal cortices with which this network is reciprocally interconnecte d. Copyright (C) 1996 IBRO. Published by Elsevier Science Ltd.