Amplitude and phase characteristics of the steady-state visual evoked potential.

The amplitude and phase characteristics of the steady-state visual evoked potential (VEP) and grating perception were studied for an unbiased group of fifteen healthy female subjects. The variability of VEP data, as obtained by using a digital sweep technique, was high between subjects but relatively low within them. Earlier claims that psychophysical detection thresholds can be predicted from VEP amplitude values were confirmed, whereas no correlation could be established between amplitude values and the perception of suprathreshold contrast. By using a principle of minimum phase difference the importance of VEP phase as an indicator of data reliability and of perceptual encoding processes could also be established.