[Influence of the spinal cord on the cerebral cortex nystagmogenic area]

We have investigated the effect of section of the spinal cord, at cervical and thoracic levels, on the excitability of the nystagmogenic area in the rabbit. Cervical transection (C2 level) induced a modification of excitability of this area since the threshold for cerebral eye nystagmus was lowered and the frequency of eye jerks was increased. Dorsal spinal transection (T4 level) did not affect the cerebral nystagmogenic area. During electrical stimulation of the dorsal quadrants of the proximal stump of the spinal cord, we found a lowering of excitability of cerebral nystagmogenic area, while ventral quadrants stimulations induced a facilitating effect on the cerebral nystagmogenic area. The evoked potentials and the responses of single units to photic stimulation of contralateral retina confirmed these results. In conclusion, the spinal cord influences the cortical nystagmogenic area by modulating its output.