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Hinze Hogendoorn, Frans A.J. Verstraten, Alan Johnston; Spatially Localized Time Shifts in Visual Experience. Journal of Vision 2010;10(7):1409. doi: https://doi.org/10.1167/10.7.1409.
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The neural encoding of an event must necessarily lag behind its occurrence in the outside world. However, we are not generally conscious of this processing delay. It is also possible to make a distinction between the time at which a neural representation of the event is formed (brain time), and the time at which we experience that event to have occurred (event time). Nevertheless, we expect that temporal relationships that exist in the world should be paralleled in visual experience. Here, we report that two synchronized running clocks appear temporally offset when one is presented in a region of the visual field previously adapted to a sequentially expanding and contracting concentric grating. After 20Hz adaptation, a clock in an adapted region appeared advanced relative to a clock in an unadapted region, whereas there was no such effect after 5Hz adaptation. The time-shift induced by adaptation cannot have been mediated by changes in the perceived speed of the clock, as 20Hz adaptation decreased, and 5Hz adaptation increased, its apparent speed. When comparing the two running clocks, observers were required to divide attention between two locations. However, the same pattern of time-shifts was also evident when observers reported the time on a single clock when exogenously cued by a visual transient. In a final experiment, we found that reaction times on a clock-hand position discrimination task presented in an adapted region did not differ for 5Hz or 20Hz adaptation, showing that the absolute time required for visual information from an adapted region to be accessed was unaffected by adaptation. Altogether, our findings show that it is possible to induce spatially localized time-shifts in visual experience. These shifts are not a result of changes in processing latency. Rather, they indicate a decoupling of visual time representation and the timing of concurrent visual events.
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