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Joel Pearson, Colin Clifford, Frank Tong; Perceptual and mnemonic contents of mental imagery revealed by binocular rivalry. Journal of Vision 2007;7(9):57. doi: 10.1167/7.9.57.
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© ARVO (1962-2015); The Authors (2016-present)
Mental imagery refers to people's ability to reconstruct perceptual experiences from memory. Controversy surrounds whether imagery relies on the same sensory representations as perception. Here, we report a collection of experiments in which we utilized binocular rivalry as a tool to reveal the perceptual and mnemonic contents of mental imagery. Observers were either shown or instructed to imagine one of two oriented patterns, several seconds prior to the presentation of an ambiguous rivalry display consisting of both competing patterns. The presentation of low luminance patterns strongly biased the perception of subsequent rivalry displays, in favor of the previously seen pattern. Remarkably, mental imagery of a specific pattern led to equally potent bias effects. Further experiments revealed that the effects of both imagery and perception were highly orientation-specific, with bias effects showing peak tuning for matching orientations. Longer periods of mental imagery led to progressively stronger bias effects, mimicking the effects of prolonged viewing of a physical pattern. These bias effects were observed even when subjects had to perform an intervening visual task prior to presentation of the rivalry display, which required attending to rapidly presented letters at central fixation. This suggests that prolonged mental imagery leads to the build-up of a short-term trace, which can endure for brief periods when observers are engaged in other tasks. Other experiments indicated that the top-down effects of imagery could be distinguished from manipulations of visual attention. Our results suggest that imagery mimics the effects of direct visual stimulation, leading to the formation of a short-term sensory trace lasting several seconds. This sensory trace can strongly bias an observer's future perceptual state under ambiguous conditions. It appears that top-down endogenous phenomena such as imagery can alter the balance of neural competition in binocular rivalry, commonly thought to transpire in early visual areas.
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