Mental Imagery Changes Multisensory Perception

Multisensory interactions are the norm in perception, and an abundance of research on the interaction and integration of the senses has demonstrated the importance of combining sensory information from different modalities on our perception of the external world [1-9]. However, although research on mental imagery has revealed a great deal of functional and neuroanatomical overlap between imagery and perception, this line of research has primarily focused on similarities within a particular modality [10-16] and has yet to address whether imagery is capable of leading to multisensory integration. Here, we devised novel versions of classic multisensory paradigms to systematically examine whether imagery is capable of integrating with perceptual stimuli to induce multisensory illusions. We found that imagining an auditory stimulus at the moment two moving objects met promoted an illusory bounce percept, as in the classic cross-bounce illusion; an imagined visual stimulus led to the translocation of sound toward the imagined stimulus, as in the classic ventriloquist illusion; and auditory imagery of speech stimuli led to a promotion of an illusory speech percept in a modified version of the McGurk illusion. Our findings provide support for perceptually based theories of imagery and suggest that neuronal signals produced by imagined stimuli can integrate with signals generated by real stimuli of a different sensory modality to create robust multisensory percepts. These findings advance our understanding of the relationship between imagery and perception and provide new opportunities for investigating how the brain distinguishes between endogenous and exogenous sensory events.