An autoradiographic study of the striatofugal fibers in the monkey.

Anterograde labelling with 3H-leucine was used to study the course and termination of striatofugal fibers in the monkey. Following injection of the isotope in the most medial part of the head and the body of the caudate nucleus fibers were traced along the ventrolateral part of the internal capsule and within the medial part of the comb bundle before penetrating the rostromedial pole of the substantia nigra (SN). Fiber endings were found along the dorsomedial edge of both divisions of the pallidum and in approximately the medial third of the SN over the whole length of this structure. Injection in the rostromedial part of the putamen resulted in silver grain concentrations representing labelled terminals in the central part of both divisions of the pallidum and in the ventrolateral and central part of the SN. Isotope concentration was equally important in both parts, reticulata and compacta, of the SN. These results favour the existence of rostrocaudal and mediolateral topographical relationships between, on the one end, the neostriatum and, on the other end, the pallidum and the SN.