Experimental Brain Research

, Volume 124, Issue 4, pp 520–524

Direct demonstration of interhemispheric inhibition of the human motor cortex produced by transcranial magnetic stimulation

  • V. Di Lazzaro
  • A. Oliviero
  • P. Profice
  • A. Insola
  • P. Mazzone
  • P. Tonali
  • J. C. Rothwell
RESEARCH NOTE

DOI: 10.1007/s002210050648

Cite this article as:
Di Lazzaro, V., Oliviero, A., Profice, P. et al. Exp Brain Res (1999) 124: 520. doi:10.1007/s002210050648

Abstract

 Electromyographic (EMG) responses evoked in hand muscles by a magnetic test stimulus over the motor cortex can be suppressed if a conditioning stimulus is applied to the opposite hemisphere 6–30 ms earlier. In order to define the mechanism and the site of action of this inhibitory phenomenon, we recorded descending volleys produced by the test stimulus through high cervical, epidural electrodes implanted for pain relief in three conscious subjects. These could be compared with simultaneously recorded EMG responses in hand muscles. When the test stimulus was given on its own it evoked three waves of activity (I-waves) in the spinal cord, and a small EMG response in the hand. A prior conditioning stimulus to the other hemisphere suppressed the size of both the descending spinal cord volleys and the EMG responses evoked by the test stimulus when the interstimulus interval was greater than 6 ms. In the spinal recordings, the effect was most marked for the last I-wave (I3), whereas the second I2-wave was only slightly inhibited, and the first I-wave (I1) was not inhibited at all. We conclude that transcranial stimulation over the lateral part of the motor cortex of one hemisphere can suppress the excitability of the contralateral motor cortex.

Key words Magnetic stimulationMotor cortexCorpus callosumDescending volleysInterhemispheric inhibition

Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • V. Di Lazzaro
    • 1
  • A. Oliviero
    • 1
  • P. Profice
    • 1
  • A. Insola
    • 2
  • P. Mazzone
    • 3
  • P. Tonali
    • 1
  • J. C. Rothwell
    • 5
  1. 1.Istituto di Neurologia, Università Cattolica, L.go A. Gemelli 8, I-00168 Rome, Italy e-mail: dilazzar@rm.ats.it Tel.: +39-06-3015-4435, Fax: +39-06-3550-1909IT
  2. 2.Neurofisiologia CTO, Via S. Nemesio 21, I-00145 Rome, ItalyIT
  3. 3.Neurochirurgia CTO, Via S. Nemesio 21, I-00145 Rome, ItalyIT
  4. 4.IRCCS, ”Casa Sollievo della Sofferenza”, San Giovanni Rotondo, ItalyIT
  5. 5.MRC Human Movement & Balance Unit, The National Hospital for Neurology & Neurosurgery, Queen Square, London WC1N 3BG, UKGB