Experimental Brain Research

, Volume 164, Issue 3, pp 323–333

Orientation-specific fast rTMS maximizes corticospinal inhibition and facilitation

Authors

  • Tobias Tings
    • Department of Clinical NeurophysiologyUniversity of Göttingen
  • Nicolas Lang
    • Department of Clinical NeurophysiologyUniversity of Göttingen
  • Frithjof Tergau
    • Department of Clinical NeurophysiologyUniversity of Göttingen
  • Walter Paulus
    • Department of Clinical NeurophysiologyUniversity of Göttingen
    • Department of Clinical NeurophysiologyUniversity of Göttingen
Research Article

DOI: 10.1007/s00221-005-2253-6

Cite this article as:
Tings, T., Lang, N., Tergau, F. et al. Exp Brain Res (2005) 164: 323. doi:10.1007/s00221-005-2253-6

Abstract

Specific stimulation of neuronal circuits may promote selective inhibition or facilitation of corticospinal tract excitability. Monophasic stimulation is more likely to achieve direction-specific neuronal excitation. In 10 healthy subjects, we compared four types of repetitive transcranial magnetic stimulation (rTMS), monophasic and biphasic stimuli with the initial current in the brain flowing antero-posteriorly (“posteriorly directed”) or postero-anteriorly (“anteriorly directed”). We applied rTMS over the primary motor cortex contralateral to the dominant hand, using 80 stimuli at 5 Hz frequency at an intensity yielding baseline motor evoked potential (MEP) amplitudes of 1 mV. Monophasic stimulation was always more efficient than biphasic. Facilitation was induced by intracerebral anteriorly directed current flow and inhibition by posteriorly oriented current flow, although only initially for approximately 30 pulses. The early inhibition was absent when studied during a tonic muscle contraction. Several mechanisms could account for these findings. They include a more efficient excitation of inhibiting circuits by posteriorly oriented pulses, and a back-propagating D-wave inhibiting early I-waves and thus inducing early inhibition of MEP amplitude. In any case biphasic rTMS results can be explained by a mixture of monophasic opposite stimulations. We propose the use of monophasic pulses for maximizing effects during rTMS.

Keywords

Transcranial magnetic stimulationMotor cortexInhibitionFacilitationD-waves and I-waves

Copyright information

© Springer-Verlag 2005