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Zhimin Chen, Ikuya Murakami, David Whitney; Interhemispheric visual temporal order adaptation. Journal of Vision 2018;18(10):715. doi: 10.1167/18.10.715.
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Perceiving the relative timing of visual events across the visual field is important for temporal grouping, motion perception, and scene recognition. However, a basic challenge to registering the synchrony of events across visual space is that information from the left and right halves of the visual field is initially processed separately in different brain hemispheres. How then does the visual system register and maintain temporal relationships such that physically synchronous information across the visual hemifields appears synchronous? Here we show that the visual system dynamically recalibrates what counts as synchronous across the left and right hemifields. Observers adapted to a sequence of random dot fields flashing on and off continuously. The spatial locations of dots on the left and right sides were mirror-symmetric. The flashing dot onsets within each hemifield were the same in the "coherent condition", and randomized in the "incoherent condition" (which avoided strong long-range motion artifacts). In both conditions, a 100 ms lag was introduced in the temporal luminance modulation between corresponding dots in the left and right hemifields. We found a negative aftereffect in subsequent temporal order judgments in both conditions: after adapting to an asynchrony across the vertical meridian, physically synchronous test stimuli appeared asynchronous. A lag (~9% of the adapting delay) was required to null the illusory temporal asynchrony. This aftereffect was specific to adaptation across the vertical but not the horizontal meridian. We further replicated the aftereffect using complex stimuli such as movie clips and dynamic fractal patterns. Our results demonstrate that the visual system calibrates the apparent timing of events selectively across the left and right halves of visual space, revealing a specialized mechanism that could help binding visual features, perceiving global patterns (e.g. symmetry), and maintaining the appearance of synchronous visual stimulation across visual space after blinks and eye movements.
Meeting abstract presented at VSS 2018
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