EQUIVALENCE BETWEEN TEMPORAL FREQUENCY AND MODULATION DEPTH FOR FLICKER RESPONSE SUPPRESSION - ANALYSIS OF A 3-PROCESS MODEL OF VISUAL-ADAPTATION

We analyze adaptation processes responsible for eliciting and alleviat ing flicker response suppression, which is a class of phenomena charac terized by the selective reduction of visual; response to the ac compo nent of a flickering light. Stimulus conditions were chosen that would allow characteristic features of flicker response suppression to be d efined and manipulated systematically. Data are presented to show that reducing the sinusoidal modulation depth of an 11-Hz stimulus can cor respond precisely to raising the temporal frequency of a fully modulat ed stimulus. In each case there is a nonmonotonic relation between fli cker response and de test illuminance. The nonmonotonic relation canno t be explained by adaptation models that postulate multiplicative and subtractive adaptation processes followed by a single static saturatin g nonlinearity, even when temporal frequency filters are incorporated into such models. A satisfactory explanation requires an additional co ntrast gain-control process. This process enhances flicker response at progressively lower temporal response contrasts as the illuminance of a surrounding adaptation field increases. (C) 1998 Optical Society of America.