The spectral sensitivities of isolated human color mechanisms determined from contrast evoked potential measurements

Abstract

Previous attempts to measure human spectral sensitivity curves by physiological methods have not yielded results with the precision and over a sufficiently wide intensity range to enable useful predictions to be made about the fine details of color vision. In the present experiment we have used a contrast evoked response technique to measure a set of spectral sensitivities whose quality is comparable to that of psychophysically obtained data. For this purpose a visual stimulus was prepared that would presumably be seen as a pattern by only one color mechanism. The EP data obtained from one rod-monochromat correspond well with the CIE 1951 scotopic relative luminous efficiency function, whereas the data from normal and dichromatic subjects resemble several of Stiles' πμ mechanisms. At the long wavelength end of the visible spectrum the relative peak sensitivities and the shapes of the spectral sensitivity functions closely agree with Stiles' π4 and π5 mechanisms. The spectral sensitivity of the short wavelength mechanism had the form of either the π1 or π3 mechanism. The dichromat results can be fitted by the same mechanisms. The long wavelength mechanism of a protanope resembled π4 and that of a deuteranope π5.