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Erin Krizay, Edward Vul, Erin Shubel, Donald I. A. MacLeod; Two timescales of orientation-contingent color adaptation. Journal of Vision 2007;7(9):271. doi: 10.1167/7.9.271.
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© ARVO (1962-2015); The Authors (2016-present)
The McCollough effect (McCollough, 1965) is an orientation-contingent color aftereffect: adaptation to (e.g.) red vertical and green horizontal gratings causes subsequent vertical and horizontal gratings to appear greenish and reddish, respectively. A peculiar trait of the McCollough effect is its unique persistence. Most aftereffects decay quickly after induction stops, persisting for not much more than the induction duration. But the McCollough effect can persist for weeks after induction. Some have attempted to explain the bizarre phenomenon of an aftereffect outlasting the adaptation period by several orders of magnitude by supposing that it is not a true aftereffect, but rather associative learning. Nonetheless, the relatively quick, constant buildup of the aftereffect suggests a more traditional process of adaptation. Here we show that the McCollough effect is a result of adaptation at two distinct timescales. The fast timescale saturates quickly and appears to have a time constant of roughly 80 seconds, much like contrast adaptation. The slow time scale shows no signs of saturation or decay in the time we measured. The existence of a second, apparently infinite, time scale suggests that the aftereffect is the sum of quick dynamic network adaptation, and permanent synaptic plasticity. The effect indeed appears to be both associative learning and a form of dynamic adaptation.
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