RT Journal Article
SR Electronic
T1 The Motor Network Reduces Multisensory Illusory Perception
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 9679
OP 9688
DO 10.1523/JNEUROSCI.3650-17.2018
VO 38
IS 45
A1 Takenobu Murakami
A1 Mitsunari Abe
A1 Winnugroho Wiratman
A1 Juri Fujiwara
A1 Masahiro Okamoto
A1 Tomomi Mizuochi-Endo
A1 Toshiki Iwabuchi
A1 Michiru Makuuchi
A1 Akira Yamashita
A1 Amanda Tiksnadi
A1 Fang-Yu Chang
A1 Hitoshi Kubo
A1 Nozomu Matsuda
A1 Shunsuke Kobayashi
A1 Satoshi Eifuku
A1 Yoshikazu Ugawa
YR 2018
UL http://www.jneurosci.org/content/38/45/9679.abstract
AB Observing mouth movements has strikingly effects on the perception of speech. Any mismatch between sound and mouth movements will result in listeners perceiving illusory consonants (McGurk effect), whereas matching mouth movements assist with the correct recognition of speech sounds. Recent neuroimaging studies have yielded evidence that the motor areas are involved in speech processing, yet their contributions to multisensory illusion remain unclear. Using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) in an event-related design, we aimed to identify the functional roles of the motor network in the occurrence of multisensory illusion in female and male brains. fMRI showed bilateral activation of the inferior frontal gyrus (IFG) in audiovisually incongruent trials. Activity in the left IFG was negatively correlated with occurrence of the McGurk effect. The effective connectivity between the left IFG and the bilateral precentral gyri was stronger in incongruent than in congruent trials. The McGurk effect was reduced in incongruent trials by applying single-pulse TMS to motor cortex (M1) lip areas, indicating that TMS facilitates the left IFG-precentral motor network to reduce the McGurk effect. TMS of the M1 lip areas was effective in reducing the McGurk effect within the specific temporal range from 100 ms before to 200 ms after the auditory onset, and TMS of the M1 foot area did not influence the McGurk effect, suggesting topographical specificity. These results provide direct evidence that the motor network makes specific temporal and topographical contributions to the processing of multisensory integration of speech to avoid illusion.SIGNIFICANCE STATEMENT The human motor network, including the inferior frontal gyrus and primary motor cortex lip area, appears to be involved in speech perception, but the functional contribution to the McGurk effect is unknown. Functional magnetic resonance imaging revealed that activity in these areas of the motor network increased when the audiovisual stimuli were incongruent, and that the increased activity was negatively correlated with perception of the McGurk effect. Furthermore, applying transcranial magnetic stimulation to the motor areas reduced the McGurk effect. These two observations provide evidence that the motor network contributes to the avoidance of multisensory illusory perception.