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Open Access Publications from the University of California

Hemispheric Asymmetry and Multisensory Learning Impact Visual Perceptual Selection

  • Author(s): Piazza, Elise Ann
  • Advisor(s): Silver, Michael A
  • Banks, Martin S
  • et al.

When visual input is consistent with multiple perceptual interpretations (e.g., the Necker cube), these interpretations compete for conscious awareness. The process of determining which interpretation will be dominant at a given time is known as perceptual selection. We study this process using binocular rivalry, a bistable phenomenon in which incompatible images presented separately to the two eyes result in perceptual alternation between the two images over time.

In one study, we showed that a well-established asymmetry in spatial frequency processing between the brain’s two hemispheres applies to perceptual selection. Specifically, a lower spatial frequency grating was more likely to be selected when it was presented in the left visual field (right hemisphere) than in the right visual field (left hemisphere), while a higher spatial frequency grating showed the opposite pattern of results. Surprisingly, this asymmetry persisted for the entire duration of a continuously presented pair of static rivaling stimuli (30 seconds), which is the first demonstration that hemispheric differences in spatial frequency processing continue long after stimulus onset.

In another study, we found that very recently formed audio-visual associations influence perceptual selection. Here, we used a brief (8-minute) crossmodal statistical learning paradigm to expose subjects to arbitrary, consistent pairings of images and sounds. In a subsequent binocular rivalry test, we found that a given image was more likely to be perceived when it was presented with a sound that had been consistently paired with it during exposure than when presented with previously unpaired sounds. Our results indicate that the audio-visual associations formed during the brief exposure period influenced subsequent visual competition and that this effect of learning was largely implicit, or unconscious.

Together, these results demonstrate an unconscious influence of complex perceptual mechanisms on perceptual selection, the process by which we form conscious representations of ambiguous sensory input.

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