Recovery Time in the Visual Cortex of Guinea Pigs and of Ground Squirrels

Abstract

The cortical irresponsive and recovery times were tested in albino guinea pigs and in ground squirrels with the same brief (1 ms) colored flashes and using the same anesthesia, dial. The irresponsive time was much longer, 60–80 ms, in the guinea pig compared with 15–20 ms in the squirrel. In the squirrel the retinal was at least 5 ms shorter than the cortical recovery time, and the retinal response reached 50 % of full amplitude when 25 ms separated the flashes compared with 100 ms for the cortical response. Since the conditioning and testing flashes had the same intensity, the irresponsive time diminished with decreasing strength of light until close to threshold in the guinea pig. The threshold was high in squirrel and flashes of maximum intensity were used with color filters. There was no difference between responses to colored flashes when the amplitude of the responses was the same, either in guinea pig or squirrel. In the guinea pig chloralose‐urethane anesthesia resulted in a longer irresponsive time, and with some light intensities there was a period when the response to the testing flash was larger than to the first flash, as has been described in cat.