Abstract
To investigate the organization of motor cortical inputs in the external (GPe) and internal (GPi) segments of the globus pallidus, we examined the responses of the GPe/GPi neurons to the stimulation of the face, arm and leg regions of the primary motor cortex (M1) and the arm and leg regions of the supplementary motor area (SMA) in a Taiwan monkey, and compared them with the responses in the subthalamic nucleus (STN). Attention was paid to the early excitation in the GPe/GPi evoked by cortical stimulation, because it is mediated by the cortico-STN projection. Neurons responding to M1 stimulation were located in the caudoventral part of the GPe/GPi, while neurons responding to SMA stimulation were found in the more dorsal and rostral part. These responsive neurons were arranged in a somatotopically organized manner. Some neurons (GPe, 35%; GPi, 20%) responded to both M1 and SMA stimulation. In the STN, neurons responding to M1 stimulation and those responding SMA stimulation were found in the dorsolateral and ventromedial parts of the STN respectively, and similar percentage of neurons (30%) responded to both stimulation. These observations suggest the somatotopically organized cortical inputs from the M1 and SMA in the GPe/GPi via the STN in spite of considerable convergent inputs from these cortical areas. [J Physiol Sci. 2008;58 Suppl:S197]
