Corticostriate projections from the primary motor cortex in the dog.

Corticostriate projections from the hindlimb and forelimb areas of the primary motor cortex in the dog were traced using the autoradiographic technique. Injections of tritiated leucine into the hindlimb area resulted in discrete oval or semicircular patches of label confined to the dorsolateral corner of the head and body of the caudate nucleus. No label was found over the putamen. Injections into the forelimb area yielded irregularly shaped patches of label over the dorsolateral part of the head and body of the caudate nucleus as well as more diffuse label over the dorsal-most part of the putamen. In both instances diffuse terminal fields were noted in the dorsolateral part of the contralateral caudate nucleus. A comparison of results in the caudate nucleus indicates that projections from the forelimb area terminate somewhat more caudally and slightly more ventrally and medially than do projections from the hindlimb area. The results further suggest that although terminal fields from these areas may to some extent interdigitate with one another, they also overlap each other to a significant degree.