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It is proposed that the acquisition and maintenance of fluent speech depend on the rapid temporal integration of motor feedforward and polysensory (auditory and somatosensory) feedback signals. In a functional magnetic resonance imaging study on 21 healthy right-handed, English-speaking volunteers, we investigated activity within these motor and sensory pathways and their integration during speech. Four motor conditions were studied: two speech conditions (propositional and nonpropositional speech) and two silent conditions requiring repetitive movement of the principal articulators (jaw and tongue movements). The scanning technique was adapted to minimize artifact associated with overt speech production. Our result indicates that this multimodal convergence occurs within the left and right supratemporal planes (STPs), with peaks of activity at their posteromedial extents, in regions classically considered as unimodal auditory association cortex. This cortical specialization contrasted sharply with the response of somatosensory association cortex (SII), in which activity was suppressed during speech but not during the silent repetitive movement of the principal articulators. It was also clearly distinct from the response of lateral auditory association cortex, which responded to auditory feedback alone, and from that within a left lateralized ventrolateral temporal and inferior frontal system, which served lexical- and sentence-level language retrieval. This response of cortical regions related to speech production is not predicted by the classical model of hierarchical cortical processing, providing new insights into the role of the STP in polysensory integration and into the modulation of activity in SII during normal speech production. These findings have novel implications for the acquisition and maintenance of fluent speech.

Original publication

DOI

10.1523/jneurosci.2607-08.2008

Type

Journal article

Journal

The Journal of neuroscience : the official journal of the Society for Neuroscience

Publication Date

10/2008

Volume

28

Pages

9969 - 9975

Addresses

Division of Neuroscience and Mental Health and Medical Research Council Clinical Sciences Centre, Imperial College London, London W12 0NN, United Kingdom. novraj.dhanjal@imperial.ac.uk

Keywords

Jaw, Tongue, Parietal Lobe, Temporal Lobe, Humans, Magnetic Resonance Imaging, Speech Production Measurement, Brain Mapping, Photic Stimulation, Speech, Perception, Auditory Perception, Speech Perception, Psychomotor Performance, Adult, Female, Male