Superior area 6 afferents from the superior parietal lobule in the macaquemonkey

Superior area 6 of the macaque monkey frontal cortex is formed by two cytoa rchitectonic areas: F2 and F7. In the present experiment, we studied the in put from the superior parietal lobule (SPL) to these areas by injecting ret rograde neural tracers into restricted parts of F2 and F7. Additional injec tions of retrograde tracers were made into the spinal cord to define the or igin of corticospinal projections from the SPL. The results are as follows: I) The part of F2 located around the superior precentral dimple (F2 dimple region) receives its main input from areas PEc and PEip (PE intraparietal, the rostral part of area PEa of Pandya and Seltzer, [1982] J. Comp. Neurol . 204:196-210). Area PEip was defined as that part of area PEa that is the source of corticospinal projections. 2) The ventrorostral part of F2 is the target of strong projections from the medial intraparietal area (area MIP) and from the dorsal part of the anterior wall of the parietooccipital sulc us (area V6A). 3) The ventral and caudal parts of F7 receive their main par ietal input from the cytoarchitectonic area PGm of the SPL and from the pos terior cingulate cortex. 4) The dorsorostral part of F7, which is also know n as the supplementary eye field, is not a target of the SPL, but it receiv es mostly afferents from the inferior parietal lobule and from the temporal cortex. It is concluded that at least three separate parietofrontal circui ts link the superior parietal lobule with the superior area 6. Considering the functional properties of the areas that form these circuits, it is prop osed that the PEc/PEip-F2 dimple region circuit is involved in controlling movements on the basis of somatosensory information, which is the tradition al role proposed for the whole dorsal premotor cortex. The two remaining ci rcuits appear to be involved in different aspects of visuomotor transformat ions. J. Comp. Neurol. 402:327-352, 1998. (C) 1998 Wiley-Liss, Inc.