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Inci Ayhan, Aurelio Bruno, Shinya Nishida, Alan Johnston; Spatial tuning of adaptation-induced temporal compression. Journal of Vision 2009;9(8):1084. doi: 10.1167/9.8.1084.
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Adaptation to high temporal frequency reduces the perceived duration of sub-second intervals. Here we explore the effects of changing spatial scale and configuration. To measure perceived duration, a grating (10Hz, 600ms) was presented at one side of fixation and the duration of a comparison, presented on the other side, varied over trials (10Hz, 350 – 850ms) to generate a psychometric function. The 50% point provided a measure of the perceived duration of the standard. To investigate small-scale lateral interactions, the standard was preceded by a mixed adaptor (20Hz interleaved with 5Hz to avoid changes in perceived temporal frequency) placed at the same position or completely above or below (0.75°, 1.50°, 2.25°). We found that the spatial tuning of the temporal compression at fine scales was a good fit to a Gaussian and remarkably tight (mean of 3 subjects; σ = 0.59°, R2 = 0.996). We also investigated adaptor size. The adaptor and stimulus height was 0.05°, 0.25°, 0.50° and 1.50° while the width was fixed at 5°. The standard was always completely overlapped the adaptor. We found little difference in compression across conditions. Even very thin adaptors produced significant duration compression. Finally, we measured the amount of temporal compression for a centre-surround spatial configuration. The adaptor was always presented in a central disc. The standard was located in an abutting annulus. We either changed the diameter of the adaptor (2°, 5°, 8°) keeping the outer diameter of the test stimuli at a fixed value (9°) or fixed the adaptor 5° and varied the outer diameter (6°, 7.5°, 9°). We found that the adaptor produced a reduction in the perceived duration for thin annuli. This effect disappeared or even induced a small temporal expansion in thicker annuli. The fine spatial tuning indicates an early locus for the temporal compression effect.
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