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| Research article summary (published 30 Aug 2003): |
Modulation of electroencephalographic responses to transcranial magnetic stimulation: evidence for changes in cortical excitability related to movement.
Full Abstract
Transcranial magnetic stimulation (TMS) and multichannel electroencephalography (EEG) were used for the investigation of cortical excitability preceding voluntary movement in human subjects. The study showed the practical value of the combined TMS-EEG approach in differentiating between cortical and spinal-cord mechanisms, which is difficult with conventional electromyographic measures alone. TMS induced a pronounced negativity (N100) lasting for 150-200 ms, with the amplitude maximum in the stimulated hemisphere. When TMS was applied just before the onset of the visually triggered movement, N100 was markedly attenuated, although motor evoked potentials (MEPs) became larger. We suggest that the N100 component represents an inhibitory response following TMS. This interpretation is in agreement with intracellular recordings in animals, paired-pulse TMS studies and experiments showing increased premovement excitability on the basis of MEPs. N100 was not affected only by the subsequent movement, but also by the switching from rest to the motor-task condition, which caused a slight attenuation of the N100 component; no changes, however, were found in the amplitude of MEPs, suggesting that modified excitability did not affect the output of the corticospinal pyramidal cells. By contrast to MEPs, N100 was modulated also by the presentation of the visual stimulus alone, i.e. when no movement was required. This attenuation suggests that even in a rest condition visual stimuli have an access to the sensorimotor regions of the cortex, most probably through ascending arousal brain systems.
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Author information
Author/s: Nikulin, Vadim V (VV); Kicic, Dubravko (D); Kähkönen, Seppo (S); Ilmoniemi, Risto J (RJ);
Affiliation: BioMag Laboratory, Engineering Centre, Helsinki University Central Hospital, Helsinki, Finland. vadim.nikulin(-atsign-)ks.se
Journal and publication information
Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't
Journal: The European journal of neuroscience (Eur J Neurosci), published in France. (Language: eng)
Reference: 2003-Sep; vol 18 (issue 5) : pp 1206-12
Dates: Created 2003/09/05; Completed 2003/10/23; Revised 2006/11/15;
PMID: 12956719, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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