Vestibular projections to the monkey thalamus: an autoradiographic study.

Vestibulothalamic projections were studied in the monkey (macaca mulatta) by injecting anerograde trace substances (radioactive leucine and proline) into the vestibular nuclear complex. Terminal labelling was found bilaterally mainly in the nucleus ventroposterior lateralis pars oralis (VPLo) and to a lesser extent in the nucleus ventroposterior inferior (VPI) and nucleus ventralis lateralis pars caudalis (VLc). The labelling was sparse, and scattered over wide areas. The vestibular origin of this projection was confirmed by injecting retrograde tracer substances (horseradish peroxidase and 125I wheat germ agglutinin) into VPLo. In the autoradiographic study no labelling was found in the posterior group.