Sound-induced Flash Illusions as a Paradigm of Multisensorial Integration: a Review Article

Sound-induced flash illusions, first described in 2000, provide a valid example of perception as a multisensorial experience where all sensorial modalities work together. Audio-visual illusions can be classified in “fission” and “fusion” illusions. Whether one flash is accompanied by two or three auditory stimuli (or beeps), it’s often perceived as multiple flashes (fission illusion), by contrast when two or more flashes are presented along with one beep, subjects often report perceiving less number of flashes (fusion illusions). Although vision has been often considered as the dominant sensory modality in humans, sound-induced flash illusions underline the leading role of acoustic stimuli in the cross-modal perception. The purpose of this review is to summarize the current knowledge about the underlying mechanisms of audiovisual illusions such as cortical excitability and connections between visual and acoustic cortex.