title: Sound-induced illusory flash perception: role of gamma band responses.
abstract: In the recently discovered sound-induced illusory flash phenomenon, a single flash accompanied with two auditory beeps is perceived as two flashes in a majority of trials. Here we asked what the neural substrates distinguishing illusion and no-illusion (i.e. perception of single flash) percepts are under identical stimulus configuration. Wavelet based method was used to analyze gamma band (> 30 Hz) responses in the event-related potential (ERP) signals recorded over visual cortical regions. We found: (i) significantly higher oscillatory and induced gamma band responses in illusion than in no-illusion trials, and (ii) significant supra-additive audio-visual interactions only in illusion trials. These results provide a clear neurophysiological correlate to the perception of illusion. Furthermore, the results suggest that auditory stimuli modulate cortical processing of visual stimuli, and the flash illusion (qualitative alteration of visual percept) only takes place when this modulation exceeds some critical threshold for the registration of conscious awareness.
authors.affiliation: Division of Biology, Mail Code 139-74, California Institute of Technology, Pasadena, CA 91125, USA. joydeep@its.caltech.edu
authors.forename: Joydeep
authors.initials: J
authors.lastname: Bhattacharya
authors.forename: Ladan
authors.initials: L
authors.lastname: Shams
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Shimojo
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001306:Auditory Pathways / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001683:Biological Clocks / Q000502:physiology; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*