The possibility that neurons in the basal ganglia and cerebellum innervate areas of cerebral cortex that are involved in cognitive function has been a contriversial subject. Here, retrograde transneuronal transport of herpes simplex virus type 1 (HSV1) was used to identify subcortical neurons that project via the thalamus to area 46 of the primate prefrontal cortex. This cortical area is known to be involved in spatial working memory. Many neurons in restricted regions of the dentate nucleus of the cerebral and in the internal segment of the globus pallidus were labeled by transneuronal transport of visus from area 46. The location of these neurons was different from those labeled after HSV1 transport from motor areas of the cerebral cortex. These observations define an anatomical substrate for the involvement of basal ganglia and cerrebellar output in higher cognitive function.