Vocal Tract Images Reveal Neural Representations of Sensorimotor Transformation During Speech Imitation.
Imitating speech necessitates the transformation from sensory targets to vocal tract motor output, yet little is known about the representational basis of this process in the human brain. Here, we address this question by using real-time MR imaging (rtMRI) of the vocal tract and functional MRI (fMRI) of the brain in a speech imitation paradigm. Participants trained on imitating a native vowel and a similar nonnative vowel that required lip rounding. Later, participants imitated these vowels and an untrained vowel pair during separate fMRI and rtMRI runs. Univariate fMRI analyses revealed that regions including left inferior frontal gyrus were more active during sensorimotor transformation (ST) and production of nonnative vowels, compared with native vowels; further, ST for nonnative vowels activated somatomotor cortex bilaterally, compared with ST of native vowels. Using test representational similarity analysis (RSA) models constructed from participants' vocal tract images and from stimulus formant distances, we found that RSA searchlight analyses of fMRI data showed either type of model could be represented in somatomotor, temporal, cerebellar, and hippocampal neural activation patterns during ST. We thus provide the first evidence of widespread and robust cortical and subcortical neural representation of vocal tract and/or formant parameters, during prearticulatory ST.
Department of Psychology, Royal Holloway, University of London, London TW20 0EX, UK.|Combined Universities Brain Imaging Centre, Royal Holloway, University of London, London TW20 0EX, UK.|The Irish Longitudinal Study on Ageing (TILDA), Department of Medical Gerontology, Trinity College Dublin, Dublin, Ireland.
Daniel
D
Carey
William Harvey Research Institute, Queen Mary, University of London, London EC1M 6BQ, UK.|Clinical Physics, Barts Health NHS Trust, London EC1A 7BE, UK.
Marc E
ME
Miquel
Department of Speech, Hearing & Phonetic Sciences, University College London, London WC1E 6BT, UK.
Bronwen G
BG
Evans
Department of Speech, Hearing & Phonetic Sciences, University College London, London WC1E 6BT, UK.
Patti
P
Adank
Department of Psychology, Royal Holloway, University of London, London TW20 0EX, UK.|Combined Universities Brain Imaging Centre, Royal Holloway, University of London, London TW20 0EX, UK.|Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, UK.
Carolyn
C
McGettigan
D000328:Adult; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007830:Larynx / Q000000981:diagnostic imaging*; D008046:Lip / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010160:Palate, Soft / Q000000981:diagnostic imaging; D066191:Sensorimotor Cortex / Q000000981:diagnostic imaging / Q000502:physiology*; D013060:Speech / Q000502:physiology*; D013061:Speech Acoustics; D014059:Tongue / Q000000981:diagnostic imaging*; D055815:Young Adult
D010100:Oxygen
FMRI; learning.; rtMRI; sensorimotor transformation; speech