The effect of stimulus orientation on the visual evoked potential in human subjects.

The average evoked potential (AEP) produced by a stationary grating of high dark-bright contrast, recorded from the human occipital scalp, was less in amplitude when it was presented obliquely than when it was oriented horizontally or vertically, and in addition the amplitude was more variable for the oblique orientation. The Wiener-filtered average method was more sensitive to these inequalities than the conventional averaging. No orientational effect upon the AEP latency was observed. Results were discussed in relation to perceptual and neuronal responses.