Posterior canal-activated vestibulocortical pathways in cats.

This study was undertaken to investigate vestibulothalamocortical pathways in anesthetized cats. Synaptic connections of posterior canal-activated excitatory vestibuloocular relay (PC) neurons to thalamic neurons were examined by a spike-triggered averaging technique. The averaged potentials evoked in the ventrobasal complex of the thalamus revealed a negative wave with latencies from 0.8 to 1.5 ms. Thirty-six thalamic neurons, which were activated by nose-up head rotation and by contralateral labyrinth stimulation, were mainly located in the ventrobasal complex. Thirteen of these neurons were antidromically activated from the anterior suprasylvian sulcus or postcruciate dimple of the cortex. These results suggest that the PC neurons participate, at least in part, in the vestibulocortical pathways contributing to spatial orientation.