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Jenny Bosten, Donald MacLeod; Mechanisms of the dimming and brightening after-effects. Journal of Vision 2011;11(11):376. doi: https://doi.org/10.1167/11.11.376.
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Dimming and brightening after-effects (Anstis 1967) occur after exposure to a temporal intensity sawtooth stimulus: a subsequently presented physically steady test field appears to become dimmer or brighter, depending on the sawtooth polarity. On a dark surround, dimming is equivalent to a loss of contrast, so these after-effects may plausibly have a contrast, as well as an intensity component. To reveal any contrast component, we used adapting stimuli that dissociated contrast and intensity gradients. We had two conditions. In the first, “contrast reducing” condition, a spatial increment of declining contrast alternated with a spatial decrement, also of declining contrast. In the second condition, the contrasts increased instead. If there is a contrast component of the dimming and brightening after-effects, the contrast-reducing condition should create a dimming after-effect for a spatially decremental test field, but a brightening after-effect for a spatially incremental test field, and vice versa. Using a nulling intensity gradient to measure the magnitude of the dimming and brightening after-effects, we found no evidence of a substantial contrast component. If the after-effects are primarily ones of intensity, we might expect to find strong after-effects for S-cone isolating stimuli. However, we found no S-cone equivalent of the dimming and brightening after-effects. We conclude that the dimming and brightening after-effects are largely based on intensity changes, though this makes it surprising that there are no after-effects for S-cone isolating stimuli.
Anstis, SM (1967) “Visual Adaptation to Gradual Change of Intensity”, Science, 155, 710-712
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