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Wonyeong Sohn, Sang-Hun Lee; Asymmetry between motion and stereo aftereffects following concurrent adaptation. Journal of Vision 2007;7(9):741. doi: 10.1167/7.9.741.
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© ARVO (1962-2015); The Authors (2016-present)
Representation of motion and stereopsis share a common set of areas along the dorsal stream of visual cortex, suggesting interactive relationships between neural substrates specialized for those two features. To explore these relationships, we measured motion and stereo aftereffects following adaptation to a stimulus defined by motion and binocular disparity.
During adaptation, observers adapted to 77 random dots moving coherently in one direction (0 deg) within a circular aperture of 2.48 deg radius. All dots drifted with the same speed (1.5 or 10 deg/sec) at the same depth (+ 0.3 deg). In the test period for motion aftereffects (MAE), we presented randomly moving dots at the same disparity as the adapting stimulus (+0.3 deg) or at the other side of fixation (− 0.3 deg). We varied the proportion of dots moving in 0 and 180 deg and observers reported the perceived direction of motion. We measured the proportion of directionally coherent dots required to cancel the MAE. For stereo aftereffects (SAE), the test dots coherently moved either in the same direction as the adaptor (0 deg) or in the opposite (180 deg). Analogously to the MAE test, we placed dots over a range of disparity (− 0.3 to + 0.3 deg) and manipulated the number of dots at crossed and uncrossed disparities. Observers reported whether the majority of dots were at the near disparity or at the far relative to fixation.
In all conditions, we observed considerable amount of aftereffects. The magnitude of the MAE was larger when the test stimulus was presented at the same disparity as adapting stimulus than when it was not. Such contingent aftereffect was not observed in the SAE. The results suggest that directional information may be coded in a stereo-dependent manner, but disparity processing is not dependent on the directions of its moving carriers.
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