Locomotor control in macaque monkeys.

We carried out experiments on young adult macaque monkeys (M.fascicularis) in an attempt to establish whether or not primates possess a locomotor control system consisting of spinal pattern generators modulated by brain-stem locomotor regions. We could not induce 'spinal stepping' in our subjects after spinal cord transection. Sparing of pathways contained in the central sector of the white matter of the cord was sufficient for stepping and walking. 'Controlled locomotion' was elicited in thalamic monkeys by electrical stimulation of the posterior subthalamic region or the midbrain tegmentum just ventral to the inferior colliculi. We conclude that there are significant homologies between this primate species and the cat regarding the probable existence of supraspinal locomotor control structures, but it seems that the presumed spinal step generators in monkeys depend more on supraspinal inputs than they do in cats.