Electrocorticographic representations of segmental features in continuous speech.
Bottom Line: Acoustic speech output results from coordinated articulation of dozens of muscles, bones and cartilages of the vocal mechanism.We found that the representation of place of articulation involved broad networks of brain regions during all phases of speech production: preparation, execution and monitoring.These results provide a new insight into the articulatory and auditory processes underlying speech production in terms of their motor requirements and acoustic correlates.
Affiliation: Inria Bordeaux Sud-Ouest/LaBRI Talence, France.
Acoustic speech output results from coordinated articulation of dozens of muscles, bones and cartilages of the vocal mechanism. While we commonly take the fluency and speed of our speech productions for granted, the neural mechanisms facilitating the requisite muscular control are not completely understood. Previous neuroimaging and electrophysiology studies of speech sensorimotor control has typically concentrated on speech sounds (i.e., phonemes, syllables and words) in isolation; sentence-length investigations have largely been used to inform coincident linguistic processing. In this study, we examined the neural representations of segmental features (place and manner of articulation, and voicing status) in the context of fluent, continuous speech production. We used recordings from the cortical surface [electrocorticography (ECoG)] to simultaneously evaluate the spatial topography and temporal dynamics of the neural correlates of speech articulation that may mediate the generation of hypothesized gestural or articulatory scores. We found that the representation of place of articulation involved broad networks of brain regions during all phases of speech production: preparation, execution and monitoring. In contrast, manner of articulation and voicing status were dominated by auditory cortical responses after speech had been initiated. These results provide a new insight into the articulatory and auditory processes underlying speech production in terms of their motor requirements and acoustic correlates.
No MeSH data available.
Mentions: We analyzed ECoG recordings to identify differential neural activity for three place of articulatory features: labial, coronal, and dorsal representing vocal-tract closures at the lips (labial), tongue tip and blade (coronal), and tongue dorsum (dorsal). We then used statistically significant, above-chance LDA classifications (AUC > 0.5) as a measure of differential neurological representations of each speech feature. We generally found statistically significant responses across the sensorimotor speech production network and auditory feedback processing regions (see left column Figure 4). The responses superior to the Sylvian fissure are distributed over the primary motor and somatosensory cortices (sensorimotor cortex for speech), while the responses in the temporal lobe are found in perisylvian auditory cortex, particularly in the posterior aspects of the superior temporal gyrus (e.g., Wernicke's area). The coronal feature resulted in the largest topographical montage of statistically significant ECoG electrodes contributing to differentiation of place of articulation (N = 19 of 401 electrodes), followed by the labial (N = 9) and dorsal (N = 3) features. A summary of these results is found in Table 4.
No MeSH data available.