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2015 ; 25
(11
): 4248-58
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An fMRI Study of the Ventriloquism Effect
#MMPMID25577576
Callan A
; Callan D
; Ando H
Cereb Cortex
2015[Nov]; 25
(11
): 4248-58
PMID25577576
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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.
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