title: Neuromodulation of multisensory perception: a tDCS study of the sound-induced flash illusion.
abstract: This study explores whether brain polarization could be effective in modulating multisensory audiovisual interactions in the human brain, as measured by the 'sound-induced flash illusion' (Shams et al., 2000). In different sessions, healthy participants performed the task while receiving anodal, cathodal, or sham tDCS (2 mA, 8 min) to the occipital, temporal, or posterior parietal cortices. We found that up- or down-regulating cortical excitability by tDCS can facilitate or reduce audiovisual illusions, depending on the current polarity, the targeted area, and the illusory percept. Specifically, the perceptual 'fission' of a single flash, due to multiple beeps, was increased after anodal tDCS of the temporal cortex, and decreased after anodal stimulation of the occipital cortex. A reversal of such effects was induced by cathodal tDCS. Conversely, the perceptual 'fusion' of multiple flashes due to a single beep was unaffected by tDCS. This evidence adds novel clues on the cortical substrate of the generation of the sound-flash illusion, and opens new attractive possibilities for modulating multisensory perception in humans: tDCS appears to be an effective tool to modulate the conscious visual experience associated with multisensory interactions, by noninvasively shifting cortical excitability within occipital or temporal areas.
authors.affiliation: Department of Psychology, University of Milano-Bicocca, Milan, Italy. nadia.bolognini@unimib.it
authors.forename: Nadia
authors.initials: N
authors.lastname: Bolognini
authors.forename: Angela
authors.initials: A
authors.lastname: Rossetti
authors.forename: Carlotta
authors.initials: C
authors.lastname: Casati
authors.forename: Flavia
authors.initials: F
authors.lastname: Mancini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Vallar
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000704:Analysis of Variance; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping; D004558:Electric Stimulation; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult