Experimental Brain Research

, Volume 155, Issue 2, pp 261–264 | Cite as

Unconscious modulation of motor cortex excitability revealed with transcranial magnetic stimulation

  • Hugo ThéoretEmail author
  • Erin Halligan
  • Masahito Kobayashi
  • Lotfi Merabet
  • Alvaro Pascual-Leone
Research Note


The neuronal effects of sensory events that do not enter conscious awareness have been reported in numerous pathological conditions and in normal subjects. In the present study, unconscious modulation of corticospinal excitability was probed in healthy volunteers with transcranial magnetic stimulation (TMS). TMS-induced motor evoked potentials (MEPs) were collected from the first dorsal interosseus muscle while subjects performed a masked semantic priming task that has been shown to elicit covert motor cortex activations. Our data show that the amplitude of the MEPs is modulated by an unseen prime, in line with temporal patterns revealed with event related potentials. These data confirm previous reports showing specific motor neural responses associated with an unseen visual stimulus and establish TMS as a valuable tool in the study of the neural correlates of consciousness.


Consciousness TMS Motor cortex Semantic priming Masking 



This work was supported by the Canadian Institutes of Health Research and the National Alliance for Autism Research (HT) and the National Institutes of Health (APL).


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Hugo Théoret
    • 1
    • 2
    Email author
  • Erin Halligan
    • 1
  • Masahito Kobayashi
    • 1
  • Lotfi Merabet
    • 1
  • Alvaro Pascual-Leone
    • 1
  1. 1.Laboratory for Magnetic Brain Stimulation, Beth Israel Deaconess Medical CenterHarvard Medical SchoolBostonUSA
  2. 2.Département de psychologie and Hôpital Ste-JustineUniversité de MontréalMontréalCanada

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