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Akiyuki Inokuma, Kazushi Maruya, Takao Sato; Enhancement of motion aftereffect by reference stimuli: a comparison between luminance and chromatic motions. Journal of Vision 2007;7(9):740. doi: 10.1167/7.9.740.
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© ARVO (1962-2015); The Authors (2016-present)
Motion aftereffect (MAE) is enhanced by static reference stimuli presented adjacent to adaptor and test stimuli. This suggests contributions of relative motion detection to MAE, but the effect is known only for MAE with luminance stimuli. Although no direct examination has been attempted, it is quite plausible that there is no reference effect for chromatic motion, since spatial integration is generally weak between chromatic motions. In the present study, we examined the reference effect with isoluminant chromatic MAE. The stimuli were moving vertical sinusoidal gratings. They were modulated along either achromatic luminance, isoluminant L-M, or isoluminant S axis in MBDKL color space. All combinations of the three stimulus types were used as adaptor/test pairs (3 × 3 design). References were rectangular-wave luminance gratings. In with-reference conditions, references were presented above and below adaptor and test throughout each trial, and results were compared with those from no reference conditions. Duration of MAE was recorded. Significant reference effect was found when adaptor and/or test stimuli were achromatic. In contrast, there was no effect when both adaptor and test were chromatic. We also conducted experiments with flickering (counterphasing) test stimuli (dynamic MAE), and found no reference effect at all. The present results, therefore, indicate that relative motion has an important role in MAE, and that relative motion is rather ineffective with chromatic inputs. The results with dynamic MAE indicate that the reference effect is a relatively low-level phenomenon. In addition, the reference effect was found when either adaptor or test alone was luminance modulated. The effect in adaptation phase can be explained by assuming strong adaptations of relative motion detectors caused by references. The effect in test phase might be accounted for by sensitivity enhancement of motion detection for luminance stimuli in the test phase.
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