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Contextual processing modulates hemispheric differences in visual perceptual selection

53.4056, Tuesday, 19-May, 8:30 am - 12:30 pm, Pavilion
Session: Binocular Vision: Rivalry and awareness

Elise Piazza1, Karen Wong2, Michael Silver2,3; 1Vision Science Graduate Program, University of California, Berkeley, 2School of Optometry, University of California, Berkeley, 3Helen Wills Neuroscience Institute, University of California, Berkeley

The right hemisphere processes low spatial frequencies (SFs) more efficiently than the left hemisphere, which preferentially processes high SFs. We employed binocular rivalry to determine how these hemispheric differences in spatial frequency processing influence visual perceptual selection from multiple SFs that are simultaneously present in the environment. Participants viewed a pair of rivalrous orthogonal gratings with different SFs, presented either to the left or right of central fixation, and they continuously reported which grating they perceived. At the onset of the rivalry pair, the low SF grating was perceptually selected (perceived) more often when it was presented in the left hemifield (right hemisphere) compared to the right hemifield (left hemisphere), whereas the high SF grating showed the opposite pattern of results. In a subsequent experiment, we found that this hemispheric asymmetry is based on relative, rather than absolute, frequency processing. For example, a medium SF grating, when rivaling with a high SF grating, was more likely to be perceptually selected when the rivalry pair was presented in the left, compared to the right, visual hemifield. However, this same medium SF grating, when it was paired in rivalry with a low SF grating, was more likely to be perceptually selected in the right, compared to the left, visual hemifield. Thus, the visual system’s classification of a given SF as “low” or “high” (and therefore, which hemisphere preferentially processes that SF) depends on the other SFs that are present in the environment at any given time, demonstrating an influence of top-down, contextual processing on hemispheric differences in visual perceptual selection and conscious representations of space.

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