Electrophysiological correlates of visual masking.

The phenomenon of paracontrast documented by means of psychophysical techniques has not been readily demonstrable using electrophysiological responses as an index of masking. We have analyzed averaged cortical potentials during presentation of visual stimuli that produce psychophysical masking. Differences in the masking profiles obtained from the two experimental conditions are apparent. However, both electrophysiological and psychophysical data do indicate an interaction between responses to an annulus and a disc which varies with the time interval between the stimuli. Both sets of data also reflect differences in masking between right and left eyes. We conclude that the cortical potentials evoked by temporally disparate stimuli do interact, but that the masking profile is not identical to the profile obtained by psychophysical methods.