Modulation of visual excitability cycles in some brain structures by high-frequency stimulation of raphe dorsal nucleus in cats.

The effect of high-frequency electrical stimulation of the raphe dorsal nucleus on the excitability cycles of the visual evoked potentials was studied. The evoked potentials to flash stimuli were recorded simultaneously in the lateral geniculate nucleus, centrum medianum, mesencephalic reticular formation, visual and associative parietal cortical areas. During stimulation of the raphe dorsal nucleus a facilitation of the visual excitability cycles in all structures studied occurred as compared to the cycles obtained before the stimulation. The analysis of the excitability cycles of the main two or three components of the visual evoked potentials revealed that the nonspecific structures were likely more involved in this activating effect than the specific ones. The data suggest that the raphe dorsal nucleus is involved in the modulation of the excitability of the visual afferent pathway and that this modulation after high-frequency stimulation of the nucleus is probably related to the increased excitability level in the nonspecific brain structures.