[Pathways and ascending vestibular projections emanating from primary nuclei: radioautographic study (author's...

A study of the pathways and ascending vestibular projections was carried out in the cat after unilateral injection of tritiated leucine into the rostral vestibular complex. Radioautographic analysis revealed a gradual decline in the density of labeling as ascending fibers were found to progress towards more rostral relays. The pathways and projections were very compact in the oculomotor nuclei, became less intense in the Cajal and Darkschewitsch nuclei, and thinned out considerably until they reached a transitional zone in the thalamus between the ventrobasal and ventrolateral complexes. These results confirm established and previous findings in this laboratory obtained by neurophysiological and neurohistological examination procedures. They provide the first anatomical evidence concerning the existence of vestibulothalamic projections and pathways.