Depression of centrum medianum complex response by rostral thalamic lesion

Abstract

In cats, lesions impinging upon the rostral pole of nuclei reticularis and ventralis anterior of the thalamus and upon the adjacent internal capsule were found to depress sensory (somatic and visual) responses in the centrum medianum complex (CM). The depression of CM responses occurred concurrently with a depression of spontaneous cortical spindles and evoked recruiting potentials. This effect did not appear to depend upon the participation of the ascending reticular activating system: CM responses to optic tract stimulation could still be depressed after bilateral destruction of the mesencephalic tegmentum. Concomitantly with the reduction of CM responses to optic tract stimulation, the responses recorded from the lateral geniculate nucleus and visual cortex were enhanced. We conclude that mechanisms entirely situated above the level of the midbrain may exert a potent tonic influence on the responsiveness of thalamic cells. Alteration of this responsiveness seems to be related to the elimination of EEG spindle waves. © 1970.