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Lee Beattie, William Curran; A role for local mechanisms in perceived duration of brief visual events. Journal of Vision 2014;14(10):1145. doi: 10.1167/14.10.1145.
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© ARVO (1962-2015); The Authors (2016-present)
Spatially localized duration compression of a briefly presented moving stimulus following adaptation in the same location is taken as evidence for modality-specific neural timing mechanisms. While it is likely that they persist to the cortical level of motion processing, there is on-going debate about where in the cortical motion pathway these mechanisms are located. The following experiments explore the contributions of local and global motion mechanisms to duration perception. In both experiments observers adapted to a unidirectional random dot stimulus (diameter 6.3 deg) presented 5 deg to one side of fixation, and then judged the duration of a 600ms test stimulus (same location) relative to a comparison stimulus on the opposite side of fixation. Presentation order of test and comparison was randomised. Experiment 1 measured duration compression of the test stimulus as a function of adaptor speed. The results revealed that duration compression is speed tuned, and that this speed tuning is well described by a log-Gaussian function. Given that a mixed-speed stimulus appears to move at its mean component speed (Watamaniuk & Duchon, 1992), we can use the speed-tuning data from experiment 1 to test the predictions of local and global models of duration compression. In experiment 2 the adaptor stimulus of Experiment 1 was replaced with a mixed-speed adaptor, with each dot assigned a fixed speed drawn from a speed range (0.75 – 5.25 deg/s) centered on 3 deg/s. Duration compression was measured as a function of the adaptor's 'speed notch' – where speed notch refers to the removal of a central band of speeds from the speed range. As speed notch increases predicted duration compression based on the adaptor's mean local speed and global speed diverges. The results were consistent with a local-mean model, demonstrating the involvement of local mechanisms in duration perception of brief visual events.
Meeting abstract presented at VSS 2014
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