Abstract
Adaptation to some stimulus dimensions has been shown to operate over multiple timescales and to reflect distinct adjustments with potentially different patterns of sensitivity change. We tested for long-term and functional changes in adaptation to chromatic contrast, in observers who had not previously been exposed to stimuli of this kind. The observers adapted to a 1 Hz sinusoidal flicker along the L vs. M chromatic axis in a uniform field presented above fixation. Test probes were interleaved with 5-sec adaptation intervals and alternated between 3 levels of +L contrast (corresponding to 0.25x, 0.5x, or 1x the peak adapt contrast). The perceived contrast at each level was tracked over time by adjusting the contrast of a nearby matching field below fixation, and continued throughout a 1-hr adapt session as well as for intervals before and after. Sessions were repeated over multiple days. Changes in perceived contrast were approximated by exponential functions and had relatively short time constants of ~ 50 sec. Both the magnitude and the time course of both the adaptation and recovery remained similar across successive days, and there was no evidence of a carry-over from preceding days. The form of the response changes also remained similar throughout the adapting period and was intermediate to a subtractive or divisive effect. Our results suggest that at least over the one-hour duration and repeated days tested, there is little evidence for a slow component in color contrast adaptation, or of a potential change in the dynamics of the adaptation with successive exposure.
Meeting abstract presented at VSS 2013