Vestibular Input To Caudate Nucleus

Unilateral stimulation of peripheral vestibular nerve branches in encephale isolé cats evoked potentials of 3- to 7-msec latency in the banks of the contralateral anterior suprasylvian sulcus and 4- to 15-msec latency in the head of the caudate nucleus bilaterally. The responses were distributed in the dorsomedial region of the ipsilateral caudate and dorsolateral region of the contralateral caudate. Stimulation of peripheral cochlear nerve branches also evoked responses in areas of caudate partially overlapping those responsive to vestibular stimulation. Stimulation of the vestibular projection area of cortex evoked a response in caudate but did not alter the response to vestibular nerve stimulation. Ablation of the vestibular projection area of cortex did not alter the vestibular responses in caudate. However, caudate and cortical responses to vestibular nerve stimulation were severely decreased by lesions of the magnocellular portion of medial geniculate body. We conclude that there are vestibular projections to the caudate nuclei which require passage through the medial geniculate body and probably other thalamic nuclei, but not through the vestibular projection area of cortex.