The equivalent background of bleaching.
Stiles and Crawford proposed that a retinal region bleached by preexposure to intense light behaves as if it were illuminated by some steady veiling or background luminance. We test this notion by comparing the afterimage of a bleaching light with a steady (and retinally stabilized) light of adjustable intensity, in the manner of Barlow and Sparrock. With their matching procedure, and also with a new procedure, we find as they did that during the rod phase of recovery the afterimage does look like a stabilized field of an intensity which, presented as a background, brings visual sensitivity to the same level. It is as if the two conditions produce equal signals at some stage of the visual pathway. Liked Barlow and Sparrock we observe a rod-cone break in the afterimage matches. However, we argue that the appearance of the rod-cone break presents a paradox and we show a way to resolve it.
Rushton
W A
WA
Department of Zoology, University of Cambridge, UK.
MacLeod
D I
DI
D000360:Afterimage / Q000502:physiology*; D003118:Color Perception / Q000502:physiology*; D006801:Humans; D008029:Lighting; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology