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Matthew Seifert, Howard Hock; Segregating Stimulus Information for Counterchange and Motion Energy Determined Motion Perception. Journal of Vision 2013;13(9):371. doi: 10.1167/13.9.371.
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© ARVO (1962-2015); The Authors (2016-present)
It has been argued that the perception of apparent motion between two spatial locations is based on the detection of counterchange (i.e., oppositely signed changes in contrast at the two locations) rather than motion energy (Hock, Gilroy & Harnett, 2002; Gilroy & Hock, 2005; Hock, Schöner & Gilroy, 2009). A constraint in furthering this distinction is that both counterchange and motion energy are present for most motion stimuli. The results of two experiments are based on specially designed stimuli for which the two kinds of motion-specifying information are segregated. Method Experiment 1 isolated the detection of counterchange. The perception of subjective squares moving across a sequence of four locations was created by pac-men at the corners of the squares, which rotated into and out of alignment over a succession of frames. Motion energy was not a factor because it was limited to the local rotation of the pac-men, which occurred during every frame and at every location, regardless of whether or not subjective squares were formed. Experiment 2 isolated the detection of motion energy. The perception of spreading luminance motion was created by luminance increments occurring sequentially across four simultaneously visible squares. Counterchange was not a factor because the luminance increments always created same-signed changes in contrast. Results Counterchange-specified motion was perceived for a wide range of frame durations, and was stronger when the subjective squares were perceived moving across smaller distances. Motion energy specified motion was preferentially perceived for brief frame durations (fast speeds). It was not stronger when the squares were closer together. If anything, motion perception tended to improve when the squares were perceived moving across greater distances, the inverse of the results for counterchange detection. Conclusions Counterchange and motion energy mechanisms for the perception of apparent motion differ in both their temporal and spatial sensitivity.
Meeting abstract presented at VSS 2013
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