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Aurelio Bruno, Inci Ayhan, Alan Johnston; Retinotopic adaptation can influence the apparent duration of a visual stimulus. Journal of Vision 2008;8(6):364. doi: 10.1167/8.6.364.
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© ARVO (1962-2015); The Authors (2016-present)
Adapting to a 20 Hz drifting grating compresses perceived duration for 10Hz stimuli displayed in the adapted location (Johnston, Arnold & Nishida, 2006, Current Biology, 16(5):472–9). However, Burr, Tozzi & Morrone (2007, Nature Neuroscience, 10(4): 423–5) described spatially selective duration effects after adaptation in both retinocentric and headcentric coordinates. They ascribed the retinotopic compression to a misrepresentation of speed. Here we investigated the effects of purely retinotopic adaptation on duration judgments. First we measured perceived speed after adaptation to an oscillating grating. The temporal frequency of the adapter was alternated between 5 and 20 Hz over time. For each subject, in different sessions, we determined the duty cycle that had no effect on perceived speed. We then used this stimulus to measure apparent duration. We adapted to an oscillating grating whose position changed continuously relative to the head, but remained constant relative to the eye. During the adaptation phase subjects tracked a fixation point that slowly oscillated across the screen. The adapter oscillated in a direction orthogonal to the eye movement. After adaptation the standard stimulus (600 ms) appeared in the last position occupied by the adapter followed by a comparison stimulus (300–1200ms) in the opposite position relative to the fixation spot. Subjects had to report which one appeared to last longer. The 50% point on the psychometric function provided a measure of the perceived duration. Continuous 5 Hz and 20 Hz adaptation conditions were also investigated. Perceived duration was reduced after adapting both to the mixed (5/20 Hz) and to the continuous 20 Hz adapter but only marginally after 5 Hz adaptation. Thus retinotopic adaptation reduces the perceived duration of a stimulus in the absence of craniotopic adaptation pointing to the existence of a retinocentric frame of reference for duration judgments.
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