The visual electrically evoked potential (VEEP): steady-state responses

The steady-state response of the visual system may provide us with complementary information about the system, when compared with transient EPs (Regan 1977). With our setup we could record such steady-state responses to electrical stimulation of the visual system for frequencies higher than about 20 Hz. We found comparatively little decline in amplitude with increasing frequency. We conclude that not much filtering is done by the system under study. The absence of pseudoflash related potentials substantiates this conclusion. Therefore it is likely that there is a constant latency for the frequencies under consideration. We also found that after some 10 cycles of the stimulating alternating current the steady-state seemed to be established. This indicates that by introducing silent periods after a limited number of stimulus cycles, recording during these periods and applying the analysis method of Diamond, the latency of the visual electrically evoked steady-state response can be determined.