Topical distribution of the striatal efferents in the monkey

Abstract Single or multiple electrolytic lesions were placed in various parts of the head of the caudate nucleus and in the putamen. The degenerated fibers were impregnated with the Nauta technique and followed to their destination. It was found that the lateral areas of the caudate nucleus project to the external segment of the globus pallidus and in lesser degree to the internal segment. Fibers from the middle part of the caudate nucleus end in both segments equally. The most medial caudate regions are connected mainly to the internal segment. The caudatonigral fibers end in the rostral substantia nigra, pars reticulata, and have a similar distribution pattern mediolaterally. This topical organization seems to exist also in the anteroposterior direction. The putamen projects to both segments of the globus pallidus and to the substantia nigra, pars reticulata, posterior to a frontal level through the oculomotor roots. There is a topical arrangement also in the putaminonigral connections anteroposteriorly. The double striatal influence from the caudate nucleus and putamen exerted upon the pallidum and substantia nigra does not overlap since the caudate fibers are distributed in the mediodorsal pallidum, while its ventrolateral remaining part receives connections from the putamen. In the substantia nigra the caudate fibers end in parts rostral to the oculomotor roots and the putaminonigral fibers terminate in areas posterior to this level.