Corticocortical inputs to the dorsal and ventral aspects of the premotor cortex of macaque monkeys.

Recent cytoarchitectonic, histochemical and physiological studies have shown that the lateral part of area 6 (the premotor cortex) of macaque monkeys can be divided into at least two subregions, each of which is considered to play an important role in motor control. One lies in the dorsal aspect of the premotor cortex (PMd) medial to the spur of the arcuate sulcus, and the other in the ventral aspect of the premotor cortex (PMv) lateral to it. Since there is little information on the corticocortical inputs to the PMd, wheat-germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was injected into both the PMd and PMv to study corticocortical inputs to these two regions, and the distribution of retrogradely labeled cells was compared. When WGA-HRP was injected into the region immediately lateral to the superior precentral sulcus within the PMd, retrogradely labeled neurons were found in area 6 lying in the mesial wall possibly corresponding to the supplementary motor area (SMA), areas 24 and 23 of the cingulate cortex, rostral region of area 4, and area 5 (area PEa). In contrast, when WGA-HRP was injected into the PMv immediately caudal to the arcuate sulcus and lateral to the spur of the arcuate sulcus, the labeled cells were found in area 7 (areas POa, PF, PFG), area 5 (area PEa), area PFop (secondary somatosensory area), SMA, the cingulate cortex (areas 24), caudal region of area 4 in the rostral bank of the central sulcus, and area 3a. It appears that the differences in the corticocortical inputs contribute to specialization of the PMd and PMv for their differential roles in motor control.