Projections of the caudate nucleus in the cat.

Circumscribed lesions of the caudate nucleus were made in four cats and two kittens. A third kitten was lesioned in the Middle Forebrain Bundle (MFB). Cats were sacrificed 8 days after the lesion and perfused intraventricularly with 10 per cent Formalin. Kittens were sacrificed 3 days after the lesion. Coronal frozen sections of the brains were made and studied under the light microscope with the Fink and Heimer staining method. Degeneration was observed in the contralateral caudate nucleus, in the homo and contralateral putamen, in the globus pallidum and in the accumbens. The substantia nigra was intensely involved as well as the red nucleus and the mesencephalic reticular formation. Patches of degeneration were also found in the superior colliculus and in the thalamus. As a preliminary conclusion we think that the projection of the caudate reaches all those structures by the middle forebrain bundle. The degeneration of the contralateral areas could be explained through a path of the anterior commissure.