Multivariate analysis of color-evoked potentials.

Transient visual-evoked cortical potentials (VECP's) were recorded for equal luminance chromatic flashes presented against a dark background and for substitutions of chromatic stimuli for achromatic fields of equal luminance. The VECP's for the flashed targets had larger amplitudes and shorter latencies than those for the substituted targets. These findings are consistent with previous psychophysical data which suggest that colored stimuli are processed in a short-latency achromatic channel and a long-latency chromatic channel. Subsequent factor analyses of the VECP's revealed a component which was interpreted as activity in the achromatic channel. These factor analyses also revealed three additional components which were tentatively identified as indications of previously undocumented high-level luminance and color processing mechanisms. Problems associated with the factor analytic approach to VECP waveform analysis are also discussed.