Multiple response of visual cortex of the rat to photic stimulation

Abstract

The primary and the later multiple responses of the visual cortex of the anesthesized (nembutal) rat to flash do not differ significantly from those recorded from the cat and rabbit under similar conditions. In the rat the multiple response consists of surface-positive potentials recurring at 160–240 msec intervals following the primary response. Intracortical recordings indicate a close correspondence in potential changes between the primary and the multiple response. Local application of strychnine sulphate did not abolish the multiple response. In the unanesthetized rat with permanently implanted cortical electrodes the late response to a single flash of light is characterized by a series of high-amplitude negative waves with sharp initially-positive activity interposed between waves. This potential complex, which has a wave-and-spike form, also recurs at 160–240 msec intervals. This response is labile and sensitive to the “arousal” level of the animal. It occurs only after the animal has “habituated” to the flash and is suppressed by novel sensory stimuli as well as high-frequency electrical stimulation of the brain stem. Control procedures show that the response is not a cortical injury potential or other artifact. The negative potentials are attenuated by nembutal anesthesia to a greater degree than the sharp positive component, and this residual activity is the multiple response recorded from the anesthetized preparation.