Effective cerebral connectivity during silent speech reading revealed by functional magnetic resonance imaging

• Published in: PloS one Vol. 8; no. 11; p. e80265
• Main Authors: Chu, Ying-Hua, Lin, Fa-Hsuan, Chou, Yu-Jen, Tsai, Kevin W-K, Kuo, Wen-Jui, Jääskeläinen, Iiro P
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 21.11.2013; Public Library of Science (PLoS)
• Subjects: Adult; Articulation (speech); Biomedical engineering; Brain; Brain - physiology; Cortex (auditory); Cortex (frontal); Cortex (motor); Cortex (premotor); Cortex (somatosensory); Cortex (temporal); Engineering; Feedback; Female; Finnish language; Functional magnetic resonance imaging; Hemodynamics; Humans; Information flow; Information management; Information processing; Language; Lipreading; Magnetic resonance; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Male; Mathematical models; Medical imaging; Neural networks; Neuroimaging; Neurology; NMR; Nuclear magnetic resonance; Phonetics; Prefrontal cortex; Reading; Resonance; Somatosensory cortex; Speech; Speech motor control; Speech perception; Speech processing; Studies; Superior temporal gyrus; Temporal cortex; Temporal gyrus; Temporal lobe; Visual cortex; Vowels; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0080265

Seeing the articulatory gestures of the speaker ("speech reading") enhances speech perception especially in noisy conditions. Recent neuroimaging studies tentatively suggest that speech reading activates speech motor system, which then influences superior-posterior temporal lobe auditory areas via an efference copy. Here, nineteen healthy volunteers were presented with silent videoclips of a person articulating Finnish vowels /a/, /i/ (non-targets), and /o/ (targets) during event-related functional magnetic resonance imaging (fMRI). Speech reading significantly activated visual cortex, posterior fusiform gyrus (pFG), posterior superior temporal gyrus and sulcus (pSTG/S), and the speech motor areas, including premotor cortex, parts of the inferior (IFG) and middle (MFG) frontal gyri extending into frontal polar (FP) structures, somatosensory areas, and supramarginal gyrus (SMG). Structural equation modelling (SEM) of these data suggested that information flows first from extrastriate visual cortex to pFS, and from there, in parallel, to pSTG/S and MFG/FP. From pSTG/S information flow continues to IFG or SMG and eventually somatosensory areas. Feedback connectivity was estimated to run from MFG/FP to IFG, and pSTG/S. The direct functional connection from pFG to MFG/FP and feedback connection from MFG/FP to pSTG/S and IFG support the hypothesis of prefrontal speech motor areas influencing auditory speech processing in pSTG/S via an efference copy.