The functional impact of mental imagery on conscious perception

Mental imagery has been proposed to contribute to a variety of high-level cognitive functions, including memory encoding and retrieval, navigation and spatial planning, and even social communication and language comprehension [1-5]. However, it is debated whether mental imagery relies on the same sensory representations as perception [1, 6-10], and if so, what functional consequences such an overlap might have on perception itself. We report novel evidence that single instances of imagery can have a pronounced facilitatory influence on subsequent conscious perception. Either seeing or imagining a specific pattern could strongly bias which of two competing stimuli reach awareness during binocular rivalry. Effects of imagery and perception were location- and orientation-specific, accumulated in strength over time, and survived an intervening visual task lasting several seconds prior to presentation of the rivalry display. Interestingly, effects of imagery differed from those of feature-based attention. The results demonstrate that imagery, in the absence of any incoming visual signals, leads to the formation of a short-term sensory trace that can bias future perception, suggesting a means by which high-level processes that support imagination and memory retrieval may shape low-level sensory representations.