The role of vestibular cortex in control of eye movements

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The presence of the "vestibular cortex" has been very controversial for a long time. More than one areas have been reported to receive vestibular information so far, but the detailed properties of vestibular inputs to the cerebral cortex are yet to be determined. This study was performed to survey the whole extent of the cortical areas that receive vestibular inputs.1. The middle ear in the monkey is located deep from the neck surface, which makes surgical approach and electrode set-up very difficult. To place the stimulating electrodes on the vestibular nerves, a new trans-middle ear approach had to be developed.2. Using the above approach, silver ball electrodes were placed near the inner ear windows and the vestibular nerves were stimulated. Evoked potentials were recorded from the cortical surface of various cortical areas. Among them, areas 2v and 6pa showed 〓〓〓quivocal responses, and laminar field analysis was performed in these areas. As a result, it is concluded that the insula … More r cortex and area 6pa receive strong vestibular inputs.3. It has been reported from laminar field analysis of the cortical responses evoked by stimulation of the thalamus in the cat and monkey that there are two kinds of the thalamocortical responses; the superficial and deep thalamocortical response. Our previous study showed that superficial and deep thalamocortical responses reflect axon terminals of thalamocortical neurons in layeis I and II, and layers III-V, respectively. Based on these findings, the present laminar field analysis of the vestibular evoked field potentials recorded in the insular cortex and area 6pa revealed that the vestibular information is relayed to the cerebral cortex by both the superficial and the deep thalamocortical projection.4. It is essential to exclude the possibility that the evoked responses that we observed are the results of the current spread to other nerves located in the middle ear; the auditory nerve and the facial nerve. These possibilities were excluded by cutting each nerve in the internal auditory canal, 01 making lesion in the ascending MLF. The results showed that the above-mentioned vestibular evoked responses were of really vestibular nerve origin.5. These results were submitted to Journal of Neuroscience. Less