Cd subdivisi of the g th :IS,in ate g CD TH, OTS mporal PRI PREFRONTAL FIG. 2.—A, Diagram of the three major subdivisions of the frontal lobe in nonhuman primates. The major sulci are the principal sulcus (PS) in prefrontal cortex, tiie arcuate sulcus (AS) that separates the prefrontal and premotor areas, and the central sulcus (CS) that is the boundary between the frontal and parietal lobes. Furdier subdivisions within prefrontal cortex are indicated: (a) inferior convexity— Brodmann's area 12; (b) cortex surrounding the principal sulcus—Brodmann's area 46; and (c) the frontal eye field—Brodmann's area 8. The mi^jor focus of the present article is Brodmann's area 46. B, Summary of areas in the posterior parietal cortex dmt process visuospatial and somatic-related infonnation (7m, lip, la, and 7b) and the distribution of their projections in die principal sulcus as revealed by correspondence in a zip-a-tone pattem (from Cavada & Coldman-Rakic, 1985), C, Summary of direct and indirect circuits linking the principal sulcus with structures involved in memory—the hippocampal formation. D, Summary ofmajor projections from the principal sulcus to areas of the brain diat are involved in motor control. Other abbreviations: IS, intraparietal sulcus; CA, Ammon's hom of the hippocampus; CC, corpus callosum; CD, caudate nucleus; CING and RS, cingulate and retrosplenial cortices; CML, caudomedial lobule; CS, collateral sulcus; DG, dentate gyms; PSUB, presubiculim; TH, TF, and 28, parahippocampal areas; OTS, occipitotemporal sulcus; SC, superior colliculus; and SMA, supplementary motor cortex