Can we estimate the activating effects of visual channels in primary visual cortex by flicker VEPs?

There are three visual channels in the primary visual cortex (V1) in monkeys, i.e., the luminance (L), color luminance (C-L), and color (C) channels. The purpose of this study was to determine how these channels extracted information from the retinal input in humans. Visual-evoked potentials (VEPs) elicited by achromatic and chromatic stimuli were recorded. Flicker VEPs elicited by different color and luminance combinations at modulating stimulus frequencies of 3-24 Hz were quantified in 10 teenagers. Two amplitude peaks at 9 and 18 Hz were observed for all types of isoluminant color combination stimuli and for achromatic stimuli at the different temporal frequencies. These temporal characteristics were modulated by color combinations and luminance changes. These findings depended strongly on the activation rates of the L, C-L, and C channels. An estimation of the activating effects of V1 cells can be obtained by summating the differential activation of each channel in response to the retinal input.