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Wakana Koshizaka, Ichiro Kuriki, Yasuhiro Hatori, Chia-huei Tseng, Satoshi Shioiri; The reversal of motion aftereffects on speed perception on color- and luminance-defined motion tested with various temporal frequency. Journal of Vision 2019;19(15):8. doi: https://doi.org/10.1167/19.15.8.
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© ARVO (1962-2015); The Authors (2016-present)
Interactions between color-defined motion (CM) and luminance-defined motion (LM) has been investigated in several psychophysical studies. In an fMRI study, we found a peculiar motion aftereffect (MAE) when adapted to long (12s) CM and tested with LM; response to motion in same direction as adaptation exhibited higher amplitude of response. In contrast, ordinary MAE was found when the adapting duration was 3s. To further investigate this phenomenon, we conducted a psychophysical experiment with a similar stimulus set up. After adapting to a rotational motion at 4 Hz for 10s, a pair of sectors of radial motion was presented as test stimulus on left and right side of the fixation point. Both test stimuli moved in the same direction (upward or downward), and the subjects reported which test stimulus appeared faster. The temporal frequency (TF) of the test stimulus was 2 Hz, 4 Hz, or 6 Hz. While 2 Hz test exhibited ordinary MAE (i.e., adapted-direction test appeared slower) subjects reported the opposite for 4 or 6 Hz test, for both CM and LM stimuli. Such reversal of MAE may reflect the property of motion mechanisms for CM and LM, sensitive to lower (<2 Hz) and higher (<4 or 6 Hz) TF, respectively. The MAE in fMRI with short (3 s) and long (12 s) adaptation may reflect the characteristics of LM and CM adaptation, respectively. Therefore, the reversal of MAE in fMRI may be reflecting the interactions of LM and CM mechanisms at high TF.
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