Organization of Corticostriatal Inputs from Presupplementary and Cingulate Motor Areas

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The cingulate motor areas reside within regions lining the cingulate sulcus and are divided into rostral and caudal parts (CMAr and CMAc). Recent electrophysiological and functional imaging studies indicate that the CMAr and CMAc are involved in distinct aspects of motor function : The former plays a role in higher-order control, whereas the latter provides an executive role. Employing double/triple anterograde axonal tracing, we investigated the organization of inputs from the CMAr and CMAc to the basal ganglia in the macaque monkey. Identified forelimb representations of the CMAr and CMAc, as well as those of the supplementary and presupplementary motor areas and the primary motor cortex, were injected with different tracers, and spatial patterns of terminal label distributions were analyzed in the striatum and the subthalamic nucleus that constitute the major input stations of the basal ganglia. Corticostriatal terminals from the CMAr and CMAc were located within the rostral striatum, with the highest density in the striatal cell bridges or the ventrolateral portion of the putamen, respectively, and displayed no substantial overlap between their distribution areas. Likewise, considerable segregation of corticosubthalamic terminal fields from the CMAr and CMAc occurred mediolaterally in the nucleus. Such corticostriatal and corticosubthalamic input zones from the CMAr or CMAc at least in part overlapped those from the presupplementary motor area or the primary motor cortex, respectively. The present data suggest that a parallel design may essentially underlie motor information processing in the cortico-basal ganglia loop arising from the CMAr and CMAc.