A neuroimaging study of premotor lateralization and cerebellar involvement in the production of phonemes and syllables.
OBJECTIVE
This study investigated the network of brain regions involved in overt production of vowels, monosyllables, and bisyllables to test hypotheses derived from the Directions Into Velocities of Articulators (DIVA) model of speech production (Guenther, Ghosh, & Tourville, 2006). The DIVA model predicts left lateralized activity in inferior frontal cortex when producing a single syllable or phoneme and increased cerebellar activity for consonant-vowel syllables compared with steady-state vowels.


METHODS
Sparse sampling functional magnetic resonance imaging (fMRI) was used to collect data from 10 right-handed speakers of American English while producing isolated monosyllables (e.g., "ba," "oo"). Data were analyzed using both voxel-based and participant-specific anatomical region-of-interest-based techniques.


RESULTS
Overt production of single monosyllables activated a network of brain regions, including left ventral premotor cortex, left posterior inferior frontal gyrus, bilateral supplementary motor area, sensorimotor cortex, auditory cortex, thalamus, and cerebellum. Paravermal cerebellum showed greater activity for consonant-vowel syllables compared to vowels.


CONCLUSIONS
The finding of left-lateralized premotor cortex activity supports the DIVA model prediction that this area contains cell populations representing syllable motor programs without regard for semantic content. Furthermore, the superior paravermal cerebellum is more active for consonant-vowel syllables compared with vowels, perhaps due to increased timing constraints for consonant production.
Ghosh
Satrajit S
SS
Speech Communication Group, Research Laboratory of Electronics, Room 36-547, Massachusetts Institute of Technology, 50 Vassar Street, Cambridge, MA 02139, USA. satra@mit.edu
Tourville
Jason A
JA
Guenther
Frank H
FH
D000328:Adult; D001303:Auditory Cortex / Q000502:physiology; D001479:Basal Ganglia / Q000502:physiology; D001931:Brain Mapping; D002531:Cerebellum / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D010700:Phonetics; D013003:Somatosensory Cortex / Q000502:physiology; D013060:Speech / Q000502:physiology*; D013788:Thalamus / Q000502:physiology