Visually evoked cortical potential (VECP) in dichromats.

The fundamental spectral sensitivity functions in man were studied by recording the visually evoked cortical potential (VECP). Using steadily presented strong blue-green and purple adaptation lights, two different spectral sensitivity functions were obtained with peaks in the green (540 nm) and in the red (590 nm) part of the spectrum. Only one peak (540 nm) was found in protanopia. The specific shift in deuteranopia and the influence of a blue-sensitive mechanism is discussed.