Perceptual distortions in visual-evoked potentials

We tested ten healthy men, ranging in age from 24 to 55 years, to determine whether "drifting" of a fixation target during pattern-stimulus testing was the result of stimulus-induced ocular movements or a purely perceptual response with no oculomotor basis. We also wanted to learn whether this drifting interfered with the development of the visual-evoked potential. We observed large intersubject differences in visual-evoked potential magnitude that could not be explained by either actual or perceived drifting. Perceived drifting did not correlate with actual or perceived drifting. Perceived drifting did not correlate with actual ocular movements. Moreover, when sporadic ocular movements occurred, they did not interfere with the visual-evoked potential; there were no correlations between magnitude of visual-evoked potential and the percentage of time that drifting was perceived.