Peripheral contrast reversal inhibits visually evoked potentials in the fovea

Abstract

Visual evoked potentials (VEP) to a 0.7° foveal test spot of different luminances projected on a white background were recorded with (1) a stationary peripheral black and white grating and (2) with contrast reversal of the peripheral grating. In the latter case, the near-threshold reduction of visibility of the test spot was accompanied by a reduction of VEP amplitude. To restore threshold visibility or to return to the former amplitude, the same luminance compensation was required. The VEP technique proved to be very sensitive; clear responses were obtained below the visibility threshold and the response curves showed saturation for a Weber ratio of only 1%.