title: Distinct mechanisms control contrast adaptation over different timescales.
abstract: Changes to the visual environment can happen at many timescales, from very transient to semi-permanent. To adapt optimally, the visual system also adjusts at different timescales, with longer-lasting environmental changes producing longer-lasting effects, but how the visual system adapts in this way remains unknown. Here, we show that contrast adaptation-the most-studied form of visual adaptation-has multiple controllers, each operating over a different time scale. In a series of experiments, subjects completed either a contrast matching, contrast detection, or tilt adjustment task, while adapting to contrast at one orientation. Following a relatively longer period (5 min) of adaptation to high contrast, subjects were "deadapted" for a shorter period (e.g., 40 s) to a lower contrast. Deadaptation eliminated perceptual aftereffects of adaptation, but continued testing in a neutral environment revealed their striking recovery. These results suggest the following account: Adaptation was controlled by at least two mechanisms, with initial adaptation affecting a longer-term one and deadaptation affecting a shorter-term one in the opposite direction. Immediately following deadaptation, the effects of the two mechanisms cancelled each other, but the short-term effects rapidly decayed, revealing ongoing longer-term adaptation. A single controlling mechanism cannot account for the observed recovery of effects, since once deadaptation cancels the initial longer-term adaptation, no trace of it remains. Combined with previous results at very long adaptation durations, the present results suggest that contrast adaptation is possibly controlled by a continuum of mechanisms acting over a large range of timescales.
authors: Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, P.R. China. baom@psych.ac.cn
authors: Min
authors: M
authors: Bao
authors: Elizabeth
authors: E
authors: Fast
authors: Juraj
authors: J
authors: Mesik
authors: Stephen
authors: S
authors: Engel
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D000360:Afterimage / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D020127:Recovery of Function / Q000502:physiology; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology*
keywords: adaptation; contrast; spontaneous recovery; timescale