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Gurjyot Singh, Gennady Erlikhman, Tandra Ghose, Zili Liu; Tilt aftereffects with orientations defined by motion or subjective contours. Journal of Vision 2012;12(9):882. doi: 10.1167/12.9.882.
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© ARVO (1962-2015); The Authors (2016-present)
We studied tilt aftereffects using orientations that were defined by different visual modalities in order to better understand visual cortical organization. Specifically, we used static subjective contours and motion trajectories to define orientations that served as adapting and test stimuli.
All stimuli were presented in a circular aperture. Randomly oriented lines drawn inside a half circle with their terminators aligned precisely along one diameter of the circle produced a vivid subjective contour along this diameter. The motion stimuli were similarly generated, except that all line terminators were rounded, thereby weakening the subjective contour. The lines moved randomly but remained along the diameter, which defined motion trajectories.
The adaptor was oriented at -15° (0° was vertical), was either static or in motion, and remained unchanged in a session. The test was either static or in motion, and was oriented either at ±1°, ±2°, ±3°, or ±4°. The adaptor was first shown for 64 sec, with each subsequent top-up for 3.2 sec. Each adaptor was followed by a 400 ms test stimulus. All 16 possible test stimuli were randomly sampled and counterbalanced. Subjects indicated whether the test was tilted left or right from 0°. The subjective 0° was estimated as a PSE of a psychometric function. The baseline subjective 0° was similarly measured from trials without any adapting stimulus.
Interestingly, for those subjects who showed the basic TAE with a static adaptor and static test, TAE was also found when the motion stimulus was either the adaptor, the test, or both. These results indicate that orientation adaptation is not necessarily restricted locally at, e.g., V2 or MT. The neural substrates of such orientation adaptations may therefore be multi-level.
Meeting abstract presented at VSS 2012
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