Cerebral and cerebellar afterdischarges in the cat

¹ Kerckhoff Laboratories of Biological Sciences, California Institute of Technology, Pasadena, California, and the Istituto di Fisiologia Umana, Milan, Italy

Single pulse stimulation of the lateral geniculate body and other optic centers in the brain stem, in addition to evoking potentials in the visual area, induced a widespread afterdischarge on the cortical surface of the brain of the cat. This discharge consists of a number of 7–13/sec. surface-positive waves. It starts from an extravisual trigger area and spreads intracortically at a speed of 0.5 mm/sec. Extracortically an afterdischarge made up of waves at half the frequency of the cortical afterdischarge was recorded from the deep nuclei of the cerebellum and from the inferior olive. This activity is induced by the cortical afterdischarges. No change occurred in pyramidal tracts activity during the afterdischarges. Sensory evoked potentials and afterdischarges did not interfere with one another. The afterdischarge did not alter the gross behavior of the animal.