Corticostriatal and corticosubthalamic input zones from the presupplementary motor area in the macaque monkey: comparison with the input zones from the supplementary motor area

The presupplementary motor area (pre-SMA) is a cortical motor-related area which lies in the medial wall of the frontal lobe, immediately anterior to the supplementary motor area (SMA). This area has been considered to partic ipate in the control of complex forelimb movements in a way different from the SMA. In an attempt to analyze the patterns of projections from the pre- SMA to the basal ganglia, we examined the distributions of pre-SMA inputs i n the striatum and the subthalamic nucleus and compared them with the SMA i nput distributions. To detect morphologically the terminal fields from the pre-SMA and the forelimb region of the SMA, anterograde tracers were inject ed into such areas that had been identified electrophysiologically in the m acaque monkey. Corticostriatal inputs from the pre-SMA were distributed mai nly in the striatal cell bridges connecting the rostral aspects of the caud ate nucleus and the putamen, as well as in their neighboring striatal porti ons. These input zones were located, with no substantial overlap, rostral t o corticostriatal input zones from the SMA forelimb region. Corticosubthala mic input zones from the pre-SMA were almost localized in the medial aspect of the nucleus, where corticosubthalamic inputs from the SMA forelimb regi on were also distributed predominantly. However, the major terminal fields from the pre-SMA were centered ventrally to those from the SMA. The present results indicate that the corticostriatal and corticosubthalamic input zon es from the pre-SMA appear to be segregated from the SMA-derived input zone s. This implies the possibility of parallel processing of motor information from the pre-SMA and SMA in the cortico-basal ganglia circuit. (C) 1999 El sevier Science B.V. All rights reserved.