title: An fMRI Study of the Ventriloquism Effect.
abstract: In spatial perception, visual information has higher acuity than auditory information and we often misperceive sound-source locations when spatially disparate visual stimuli are presented simultaneously. Ventriloquists make good use of this auditory illusion. In this study, we investigated neural substrates of the ventriloquism effect to understand the neural mechanism of multimodal integration. This study was performed in 2 steps. First, we investigated how sound locations were represented in the auditory cortex. Secondly, we investigated how simultaneous presentation of spatially disparate visual stimuli affects neural processing of sound locations. Based on the population rate code hypothesis that assumes monotonic sensitivity to sound azimuth across populations of broadly tuned neurons, we expected a monotonic increase of blood oxygenation level-dependent (BOLD) signals for more contralateral sounds. Consistent with this hypothesis, we found that BOLD signals in the posterior superior temporal gyrus increased monotonically as a function of sound azimuth. We also observed attenuation of the monotonic azimuthal sensitivity by spatially disparate visual stimuli. The alteration of the neural pattern was considered to reflect the neural mechanism of the ventriloquism effect. Our findings indicate that conflicting audiovisual spatial information of an event is associated with an attenuation of neural processing of auditory spatial localization.
authors.affiliation: Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Callan
authors.affiliation: Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Daniel
authors.initials: D
authors.lastname: Callan
authors.affiliation: Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ando
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001303:Auditory Cortex / Q000098:blood supply / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D011571:Psychoacoustics; D011930:Reaction Time / Q000502:physiology; D013017:Sound Localization / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: auditory; fMRI; multimodal integration; spatial processing; ventriloquism