SPECTRAL SENSITIVITY OF VISUAL-EVOKED POTENTIALS ELICITED BY SHIFTINGMONOCHROMATIC CHECKERBOARD PATTERNS .1. NORMAL OBSERVERS

1. This investigation was designed to isolate responses from the short wavelength sensitive (SWS; ''blue''), middle wavelength sensitive (MW S; ''green'') and long wavelength sensitive (LWS; ''red'') sensitive c one mechanisms by recording visual evoked potentials (VEP) in response to a shifting monochromatic checkerboard pattern. 2. Twenty-four norm al trichromatic observers, as determined by the Farnsworth Munsell 100 -Hue test, were evaluated. A two-beam Maxwellian view system served to present a circular test field (subtending 13.3-degrees in diameter), consisting of a checkerboard pattern with a check size of 1.32-degrees , which was moved back and forth for one check length at a 3 Hz tempor al frequency. The test field was concentrically superimposed upon a mo nochromatic adapting field which was 42.5-degrees in diameter. 3. For each of three wavelengths of the adapting field (489, 574 and a mixtur e of 422 and 630 nm), VEPs (400 sweeps) were recorded from 01 and 02 i n response to five monochromatic test wavelengths. The test field inte nsities were increased from the sensory threshold in steps of approx. 0.3 log units up to response saturation. 4. By interpolation from the obtained V-log I functions, a low amplitude criterion of the second ha rmonic component, as determined by Fourier analysis, was chosen and th e stimulus irradiance required for this criterion was plotted against stimulus wavelength. 5. The resulting spectral sensitivity curves from each cone mechanism fitted rather well the Stiles pi1, pi4 and pi5 fu nctions corrected for loss in the ocular media. 6. This new technique proved to be an objective and reliable tool which might be of value in quantifying colour vision disturbances caused by different diseases.