Listening to speech recruits specific tongue motor synergies as revealed by transcranial magnetic stimulation and tissue-Doppler ultrasound imaging.
The activation of listener's motor system during speech processing was first demonstrated by the enhancement of electromyographic tongue potentials as evoked by single-pulse transcranial magnetic stimulation (TMS) over tongue motor cortex. This technique is, however, technically challenging and enables only a rather coarse measurement of this motor mirroring. Here, we applied TMS to listeners' tongue motor area in association with ultrasound tissue Doppler imaging to describe fine-grained tongue kinematic synergies evoked by passive listening to speech. Subjects listened to syllables requiring different patterns of dorso-ventral and antero-posterior movements (/ki/, /ko/, /ti/, /to/). Results show that passive listening to speech sounds evokes a pattern of motor synergies mirroring those occurring during speech production. Moreover, mirror motor synergies were more evident in those subjects showing good performances in discriminating speech in noise demonstrating a role of the speech-related mirror system in feed-forward processing the speaker's ongoing motor plan.
Robotics Brain and Cognitive Sciences Department, RBCS, Italian Institute of Technology, IIT, , via Morego, 30, Genova 16163, Italy.
A
A
D'Ausilio
L
L
Maffongelli
E
E
Bartoli
M
M
Campanella
E
E
Ferrari
J
J
Berry
L
L
Fadiga
D000161:Acoustic Stimulation; D001696:Biomechanical Phenomena; D004525:Efferent Pathways / Q000502:physiology*; D006309:Hearing / Q000502:physiology*; D006801:Humans; D059167:Mirror Neurons / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology*; D014059:Tongue / Q000166:cytology / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D018608:Ultrasonography, Doppler
mirror neurons; motor synergies; motor theory of speech perception; speech perception; tongue; transcranial magnetic stimulation