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Temporal analysis of the multifocal cortical visual evoked potential (VEP) was studied using pseudo-random (m-sequence) achromatic stimulation. The effects of variation of luminance contrast on the first-order response were complex. At low to mid contrasts (<60%), a wave doublet (P100-N115) predominated. A second wave complex (N100-P120-N160) dominated at high contrasts. The second-order responses, however, showed an extremely simple variation with luminance contrast. Intrinsic differences in the adaptation time of the generators of these two components caused a distinct separation in the slices of the second-order response. A rapidly adapting nonlinearity saturating at low contrasts was only observable when measuring the responses from two consecutive flashes. Its latency coincided with the contrast saturating first-order response component. By comparison, the nonlinearity derived from the …