Stimulation of Semicircular Canal Afferents Vestibuloocular Reflex Adaptation Investigated With Chronic Motion-Modulated Electrical (original) (raw)

Ris, Laurence and Emile Godaux. Neuronal activity in the vestib-metries caused by a unilateral labyrinthectomy the driving force for restoration of activity? Here, we addressed these two questions ular nuclei after contralateral or bilateral labyrinthectomy in the alert guinea pig. J. Neurophysiol. 80: 2352Neurophysiol. 80: -2367Neurophysiol. 80: , 1998. In the by studying the spiking behavior of 473 second-order vestibular neurons in the alert guinea pig after a bilateral labyrinthectomy. guinea pig, a unilateral labyrinthectomy is followed by an initial depression and a subsequent restoration of the spontaneous activity In the acute stage, 1 h after bilateral labyrinthectomy, the resting discharge of the second-order vestibular neurons was 16.2 { 22.4 in the neurons of the ipsilateral vestibular nuclei. In two previous works, we have established the time course of these changes in spikes/s. From comparison with the results obtained in the acute stage after a unilateral labyrinthectomy, we inferred that the ipsilat-the alert guinea pig using electrical stimulation as a search stimulus to select the analyzed neurons. The latter criterion was important eral excitatory influence was between two and three times more powerful than the contralateral inhibitory influence. After bilateral to capture the many ipsilateral neurons that are silent at rest during the immediate postlabyrinthectomy stage. Because it is known that labyrinthectomy as well as after unilateral labyrinthectomy, the resting activity of the second-order vestibular neurons returned to a pathway originating from the vestibular nuclei on one side crosses the midline and functionally inhibits the activity of the vestibular normal, reaching 20.8 { 23.1 spikes/s 1 day after the lesion and 38.6 { 21.1 spikes/s 1 wk after the lesion. From this fact, we nuclei on the other side, we investigated in the first part of this study the spiking behavior of the neurons in the vestibular nuclei concluded that the left-right asymmetries caused by a unilateral labyrinthectomy were not the error signals inducing the restoration contralateral to the labyrinthectomy using the same procedure as that used for the ipsilateral neurons. The spiking behavior of 976 of activity. neurons was studied during 4-h recording sessions in intact animals and 1 h, 1 day, 2 days, or 1 wk postlabyrinthectomy. Neurons I N T R O D U C T I O N selected according to the electrical activation criterion were classified further as type I (their firing rate increased during ipsilateral 0022-3077/98 $5.00