Cortical Connectivity Suggests a Role in Limb Coordination for Macaque Area PE of the Superior Parietal Cortex

In macaques, superior parietal lobule area 5 has been described as occupying an extensive region, which includes the caudal half of the postcentral convexity as well as the medial bank of the intraparietal sulcus. Modern neuroanatomical methods have allowed the identification of various areas within this region. In the present study, we investigated the corticocortical afferent projections of one of these subdivisions, area PE. Our results demonstrate that PE, defined as a single architectonic area that contains a topographic map of the body, forms specific connections with somatic and motor fields. Thus, PE receives major afferents from parietal areas, mainly area 2, PEc, several areas in the medial bank of the intraparietal sulcus, opercular areas PGop/PFop, and the retroinsular area, frontal afferents from the primary motor cortex, the supplementary motor area, and the caudal subdivision of dorsal premotor cortex, as well as afferents from cingulate areas PEci, 23, and 24. The presence and relative strength of these connections depend on the location of injection sites, so that lateral PE receives preferential input from anterior sectors of the medial bank of intraparietal sulcus and from the ventral premotor cortex, whereas medial PE forms denser connections with area PEc and motor fields. In contrast with other posterior parietal areas, there are no projections to PE from occipital or prefrontal cortices. Overall, the sensory and motor afferents to PE are consistent with functions in goal-directed movement but also hint at a wider variety of motor coordination roles.