Spread of Responses in the Cerebral Cortex to Meaningful Stimuli

Abstract

THE primary visual receiving area of the mammalian cerebral cortex is readily excited by sudden alterations in the intensity of light falling on either retina. Techniques developed by Hubel and Wiesel⁴ have made it possible to record the responses of individual cortical neurones to appropriately placed retinal stimuli of the right shape. The response of single units to the proper form of physiological stimulus is sometimes so clear that a single flash or movement of a pattern of light in the visual field will invariably produce a burst of discharges from the recorded neurone. Most neurones in the lightly anaesthetized or unanaesthetized visual cortex, however, are less predictable in their behaviour, and their response to retinal excitation is best demonstrated by averaging procedures². A post-stimulus histogram (PSH) is obtained, which displays the number of neuronal discharges occurring at various times after each of a series of identical retinal stimuli. Thus the PSH indicates the distribution of probability of unit discharge, following visual excitation.