Resolution of the region of secondary somatosensory cortex that responds to stimulation of the horizontal semicircular canal in rats

To elucidate the region within the somatosensory cortex that receives inputs from the horizontal semicircular canal (HSC) in rats, we used a multichannel recording system to measure evoked potentials in the parietal cortex in response to electrical stimulation of the HSC nerve. The recordings suggested that the HSC nerves projected bilaterally into the somatosensory cortex, with a contralateral predominance. The territory within the somatosensory cortex that responded to the stimulation of the HSC nerve was as follows: mediolateral 6.0 mm and anteroposterior –1.3 ∼ –2.3 mm from the bregma, and depth 1.4 ∼ 1.6 mm from the cortex surface horizontally by stereotaxic atlas. The evoked potential in the parietal cortex that was induced by electrical stimulation was abolished after the administration of tetrodotoxin into the oval window of the vestibular system. These results suggest that the horizontal semicircular nerve projects bilaterally into the deep layers of the secondary somatosensory cortex.