COLOUR SPECIFIC FEATURES OF VISUAL CORTICAL RESPONSES IN MAN EVOKED BY MONOCHROMATIC FLASHES

In 16 normal human subjects a study was made of averaged responses in the occipital regions to monochromatic flashes of 15 different wavelengths with equal energy. The responses to monochromatic flashes were found to have the same principal components as those previously shown in responses to white light. With low intensity flashes of equal energy, the latencies of all components were shortest in the middle range (514–576 mix), longer in the blue, and longest in the red end of the spectrum. With high intensity stimuli, the latencies were in general shorter, and did not vary with wavelength. The high variability of the amplitudes of the evoked responses made it difficult to correlate amplitude with wavelength. However, some individual curves, as well as the average amplitude/wavelength curve for the whole group of 16 subjects, showed partly significant peaks at 453–475, 551 and at 615 mix, a finding which appears to support the existence of a trichromatic colour receptor mechanism in man. One group of the subjects showed a strikingly stable form of the evoked responses, but varying amplitudes of separate components at different wavelengths. Another group showed very stable forms of the responses which appeared specific to wavelength. © 1969 Scandinavian Physiological Society