1. Title Convergence between semicircular canal and otolith nerves on single vestibulo-ocular and vestibulospinal neurons of the decerebrate cat 2.Author

Convergence between semicircular canal and otolith nerves on single vestibulo-ocular and vestibulospinal neurons of the decerebrate cat 2.Author We examined whether otolith-activated second-and third-order vestibular nucleus neurons received commissural inhibition from the contralateral otolithic macula oriented in the same geometric plane. For this purpose we have studied intracellular recording in vestibular nucleus neurons after stimulation of the ipsi-and contralateral utricular and saccular nerves. More than half (41/72) of the utricular-activated second-order vestibular nucleus neurons received commissural inhibition from the contralateral utricular nerve. The remaining neurons (31/72) showed no visible response to contralateral utricular nerve stimulation. About half (17/36) of utricular-activated third-order neurons also received commissural inhibition from the contralateral utricular nerve. Approximately 10 % (7/67) of saccular-activated second-order vestibular neurons received polysynaptic commissural inhibition, whereas 16% (11/67) received commissural facilitation. The majority (49/67) of saccular second-order vestibular neurons, and almost all (22/23) third-order neurons, showed no visible response to stimulation of the contralateral saccular nerve. The present findings suggest that many utricular-activated vestibular nucleus neurons receive commissural inhibition, which may provide a mechanism for increasing the sensitivity of vestibular neurons to horizontal linear acceleration and lateral tilt of the head. Commissural inhibition in the saccular system was less prominent than in the utricular system. Å@ (11) Convergence of the horizontal semicircular canal and otolith afferents on cat single vestibular neurons. Exp We studied the convergence of two afferent pairs of single vestibular neurons by selective stimulation of the horizontal semicircular canal (HC) and saccular (SAC) nerves, and the HC and utricular (UT) nerves in decerebrated cats. All recorded neurons were classified as vestibulospinal (VS), vestibulooculospinal (VOS), vestibuloocular (VO), by antidromic stimulation from the oculomotor/trochlear nuclei and the spinal cord: neurons that could not be activated from any test sites were classified as vestibular (V) neurons. Of a total of 125 neurons activated by stimulation of the HC/SAC nerves, 21(17%) received convergent inputs. Twelve of 21 neurons received monosynaptic