Projections of the vestibular nuclei to the thalamus in the rat: a Phaseolus vulgaris leucoagglutinin study.

Injections of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin were made into individual nuclei of the vestibular nuclear complex of the rat to identify specific projections to the thalamus. The results showed that the superior vestibular nucleus and the medial vestibular nucleus, especially its rostral-to-middle parts, project to the lateral part of the parafascicular thalamic nucleus (corresponding to the centromedian nucleus in primates), the transitional zone between the ventrolateral thalamic nucleus (VL) and the ventral posterolateral thalamic nucleus (VPL) (the region considered to be the nucleus ventralis intermedius of Vogt [Vogt C. 1909. La myeloarchitecture du thalamus du cercopitheque. J Psychol Neurol 12:285-324.]), the lateral part of the centrolateral thalamic nucleus and the dorsal part of the caudal VL; the spinal vestibular nucleus projects to the lateral part of the parafascicular thalamic nucleus, the transitional zone between the VL and the VPL, the caudal part of the ventrobasal complex, and the suprageniculate thalamic nucleus. These results suggest that vestibular information is transmitted not only to the cerebral cortex (mainly area 2V and area 3a) but also to the striatum. They also suggest that vestibular activity may affect gaze control by means of vestibulothalamocortical pathway in addition to vestibulo-ocular and vestibulopremotoneuronal routes.