Losses of foveal flicker sensitivity during dark adaptation following extended bleaches.
Flicker sensitivity to a small foveal test stimulus can decrease appreciably during the period of dark adaptation that follows extinction of a bleach. For 20 min diameter, long wavelength tests that followed 70% L cone bleaches of various wavelengths, 18 Hz flicker sensitivity decreased precipitously (i.e. within about 45 sec) by about 1.5-2.0 log units beginning at about 100-200 sec following extinction of the bleach. For short wavelength tests that followed long wavelength bleaches, the corresponding precipitous losses of flicker sensitivity were relatively small and early; flicker sensitivity decreased by about 0.6-1.0 log units beginning no later than 60 sec following extinction of the bleach. Whenever flicker sensitivity decreased precipitously, the losses of flicker sensitivity were followed by plateaus of M cone dominated flicker sensitivity. For combinations of test and bleaching wavelengths that did not cause flicker sensitivity to decrease precipitously, flicker sensitivity instead decreased gradually over a prolonged period of time, and incorporated a substantial L cone contribution. The precipitous suppression of flicker sensitivity found for certain combinations of bleaching and test wavelengths appears to depend on the action of a broadly tuned, red-green spectrally opponent process.
Eisner
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A
R. S. Dow Neurological Sciences Institute, Portland, OR.
D000328:Adult; D002138:Calibration; D003623:Dark Adaptation / Q000502:physiology*; D005260:Female; D005425:Flicker Fusion / Q000502:physiology*; D005584:Fovea Centralis / Q000502:physiology*; D006801:Humans; D008027:Light; D008266:Macula Lutea / Q000502:physiology*; D008297:Male; D010775:Photic Stimulation / Q000295:instrumentation / Q000379:methods; D010786:Photoreceptor Cells / Q000502:physiology*