Prolonged changes in visual system activity produced by somatic stimulation

Abstract

The tonic electrical activity in the visual radiations and lateral geniculate nucleus was recorded in anesthetized cats. It was found that somatic stimulation, such as rubbing a paw, vibration of the skin, or electrical stimulation of the sciatic nerve, frequently produces marked, prolonged decreases in the tonic activity. The majority of the changes have durations of 3–12 min, but sometimes last for more than 30 min. Prolonged increases in tonic activity are also occasionally observed. The prolonged changes, characteristically observed when the cats are in a state of moderate anesthesia, are abolished by large doses of barbiturate, but are still seen when the animal is light enough for paw pinch to produce with-drawal reflexes. Control experiments show that changes in EEG, blood pressure, and intraocular pressure may occur concomitantly with stimulation but are not the causal mechanisms of the prolonged activity changes. The fact that the prolonged changes are abolished by lesions of the anterolateral pathways but not of the dorsal columns suggests that the reticular formation may mediate the effects of the somatic input on visual system activity.