Focal and diffuse metabolic changes in the spinal cord of the monkey elicited by microstimulation of differing motor cortical foci.

The pattern of projections from identified motor cortical efferent zones onto the spinal cord was examined in the monkey using a combination of microstimulation and [14C]2-deoxyglucose metabolic labeling. Regional differences were found in the branching patterns between the projections of proximal and distal forelimb foci of the motor cortex onto the spinal cord. Cortical efferent zones related to proximal movements project extensively within the spinal cord activating numerous motor nuclei. In contrast, the corticospinal projection of a distal movement zone was found to be significantly more restricted in overall rostrocaudal extent projecting with greatest density onto a small focal region of the ventrolateral horn.