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Stimulating language: insights from TMS

Open Access
Joseph T. Devlin, Kate E. Watkins
DOI: http://dx.doi.org/10.1093/brain/awl331 610-622 First published online: 29 November 2006

Summary

Fifteen years ago, Pascual-Leone and colleagues used transcranial magnetic stimulation (TMS) to investigate speech production in pre-surgical epilepsy patients and in doing so, introduced a novel tool into language research. TMS can be used to non-invasively stimulate a specific cortical region and transiently disrupt information processing. These ‘virtual lesion’ studies offer not only the ability to explore causal relations between brain regions and language functions absent in functional neuroimaging, but also spatial and temporal precision not typically available in patient studies. For instance, TMS has been used to demonstrate functionally distinct sub-regions of the left inferior frontal gyrus; to clarify the relationship between pre-morbid language organization and susceptibility to unilateral lesions and to investigate the contribution of both left and right hemisphere language areas in recovery from aphasia. When TMS is used as a measure of functional connectivity, it demonstrates a close link between action words and motor programmes; it suggests a potential evolutionary link between hand gestures and language and it suggests a role in speech perception for the motor system underlying speech production. In combination with functional neuroimaging, it can elucidate the circuits responsible for this involvement. Finally, TMS may even be useful for enhancing recovery in aphasic patients. In other words, TMS has already become an important tool for studying language at both the cognitive and neural levels, and it is clear that further developments in TMS methodology are likely to result in even greater opportunities for language research.

  • virtual lesion
  • functional connectivity
  • aphasia
  • Abbreviations:
    Abbreviations:
    DLPFC
    dorso-lateral prefrontal cortex
    IAT
    intra amytal test
    LIFG
    left inferior frontal gyrus
    MEP
    motor evoked potential
    RIFG
    right inferior frontal gyrus
    RT
    reaction time
    rTMS
    repetitive TMS
    TMS
    transcranial magnetic stimulation

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