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Fang Fang, Sheng He; Weak motion aftereffect from a square wave test. Journal of Vision 2003;3(9):597. doi: 10.1167/3.9.597.
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© ARVO (1962-2015); The Authors (2016-present)
In a complete linear system, the behavior of a square wave pattern can be predicted by its sinusoidal components. However, we observed a complete breakdown of the linear system prediction in the perception of motion aftereffect (MAE).
The duration of the MAE was measured following a one-minute adaptation to a rotating radial grating. Four different luminance patterns were used for both the adapt and test stimulus: 1. sine wave, 2. square wave, 3. complex grating composed of the 1f, 3f, 5f and 7f harmonic components of the square wave grating, and 4. complex grating with the same components as 3, but with randomized phases. The sine wave stimulus generated the highest magnitude MAE, followed by the random-phase complex grating, then the square-wave-like complex grating, and lastly the square wave grating.
To test whether the square wave grating is a weak adapter or a weak test for the MAE, we performed a cross adaptation experiment in which the sine wave and square wave gratings were paired in all four possible ways. Results show that both sine and square wave adaptation generated a strong MAE for the sine wave test, but neither induced nearly as strong of a MAE when tested with a static square wave grating. Further experiments ruled out the possibility that differential MAEs between these conditions are due to different peak contrasts in these patterns.
Linear system theory cannot predict the magnitude of the MAE in complex gratings. The spatial features of a test stimulus such as position reliability or luminance uniformity strongly influence the magnitude of the MAE. Sharp edges and local luminance uniformity can greatly reduce the MAE.
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