The human visual evoked cortical potential and dark adaptation

The relationship between the amplitude of the human visual evoked cortical potential (VECP) and dark adaptation was examined in three normal subjects. In addition, the VECP dark adaptation functions were compared with psychophysical functions obtained in the same sessions under identical stimulus conditions. In order to separate the rod and cone systems two chromatic stimuli were used, one from the short wavelength and the other from the long wavelength portion of the visible spectrum. The results indicate that the VECP is a sensitive correlate of both rod and cone adaptation since the VECP dark adaptation changes parallel the psychophysical threshold changes. It was concluded that the VECP is an excellent tool for investigating both cone and rod dark adaptation when the appropriate methods and conditions for study are used.