Short-term modulation of regional excitability and blood flow in human motor cortex following rapid-rate transcranial magnetic stimulation

Beatrice Takano, Alexander Drzezga, Martin Peller, Iris Sax, Markus Schwaiger, Lucy Lee, Hartwig Roman Siebner

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


Repetitive transcranial magnetic stimulation (rTMS) of the human primary motor cortex (M1) provides a means of inducing lasting changes in cortical excitability and synaptic activity. Here we combined rTMS with positron emission tomography of regional cerebral blood flow (rCBF) to examine how an rTMS-induced change in intracortical excitability of inhibitory circuits affects regional synaptic activity. In a first set of experiments, we gave 150 biphasic pulses of 5 Hz rTMS at 90% of active motor threshold to left M1 and used single- and paired-pulse TMS to assess the conditioning effects of rTMS on motor cortical excitability at rest. rTMS conditioning led to a selective decrease in short-latency intracortical inhibition (SICI) without affecting short-latency intracortical facilitation or corticospinal excitability. The decrease in SICI lasted for approximately 8 min. In a second experiment, we used the same rTMS protocol and measured changes in regional synaptic activity (as indexed by rCBF) during and for up to 14 min after the end of rTMS. Subthreshold 5 Hz rTMS induced a region-specific increase in resting rCBF in the stimulated M1 lasting approximately 8 min. These \ suggest that in the stimulated M1, temporary attenuation of SICI is paralleled by an increase in synaptic activity, consistent with reduced efficacy of intracortical GABA A-ergic synapses. The present findings demonstrate that short trains of low-intensity 5 Hz rTMS can be used to induce a transient change in function within a distinct cortical area. This opens up new possibilities for studying acute reorganization at the systems level in the intact human brain.

Original languageEnglish
Pages (from-to)849-859
Number of pages11
Issue number3
StatePublished - Nov 2004


  • Functional imaging
  • Inhibition
  • Motor cortex
  • Regional cerebral blood flow
  • Synaptic activity
  • Transcranial magnetic stimulation


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