The interhemispheric projection from the substantia nigra to the caudate-putamen as depicted by the anterograde transport of [3H]leucine.

The organization of the interhemispheric projections from the substantia nigra to the caudate-putamen was examined after [3H]leucine had been injected into the substantia nigra on one side. There was not a strict correspondence between the regions of termination of the crossed and homolateral nigrostriatal projections. Although the leucine predominantly labeled the lateral parts of the ipsilateral caudate-putamen, terminal labeling was also found in the medial and lateral parts of the contralateral caudate-putamen. The crossed nigrostriatal projection terminated in discrete areas of variable size in the contralateral caudate-putamen. The patterns made by the silver granules in the caudate-putamen contralateral to the [3H]leucine injection appeared to be heterogeneous.