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. 2011 May 18:12:45.
doi: 10.1186/1471-2202-12-45.

Enhancing the effect of repetitive I-wave paired-pulse TMS (iTMS) by adjusting for the individual I-wave periodicity

Sebastian Sewerin  1 , Marco Taubert, Henning Vollmann, Virginia Conde, Arno Villringer, Patrick Ragert
Affiliations

Enhancing the effect of repetitive I-wave paired-pulse TMS (iTMS) by adjusting for the individual I-wave periodicity

Sebastian Sewerin et al. BMC Neurosci. .

Abstract

Background: Repeated application of paired-pulse TMS over the primary motor cortex (M1) in human subjects with an inter-pulse interval (IPI) of 1.5 ms (iTMS(1.5 ms)) has been shown to significantly increase paired-pulse MEP (ppMEP) amplitudes during the stimulation period and increased single-pulse MEP amplitudes for up to 10 minutes after termination of iTMS.

Results: Here we show in a cross-over design that a modified version of the iTMS(1.5 ms) protocol with an I-wave periodicity adjusted to the individual I1-peak wave latency (iTMS(adj)) resulted in a stronger effect on ppMEPs relative to iTMS(1.5 ms).

Conclusions: Based on these findings, our results indicate that the efficiency of iTMS strongly depends on the individual choice of the IPI and that parameter optimization of the conventional iTMS(1.5 ms) protocol might improve the outcome of this novel non-invasive brain stimulation technique.

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Figures

Figure 1
Figure 1
Increased ppMEPs during iTMS1.5 ms. Group mean ppMEP increase [%] during 10 minutes of conventional iTMS1.5 ms normalized to the first minute of stimulation (n = 16). Group mean data is presented as mean ± s.e.m. Note that there was a significant increase in ppMEP facilitation during intervention. For details see text.
Figure 2
Figure 2
Distribution of individual I1-wave peak latencies [ms] in all subjects tested (n = 16). § indicates that three subjects with an individual I1-wave peak latency of 1.5 ms were excluded from further analysis in order to compare the efficacy of iTMSadj relative to iTMS1.5 ms.
Figure 3
Figure 3
Comparison between iTMS1.5 ms and iTMSadj. Group mean ppMEPs increase [%] during 10 minutes of conventional iTMS1.5 ms and iTMSadj (n = 13). Please note that there was a significant difference between the amounts of ppMEP facilitation between both interventions. For details see text.
Figure 4
Figure 4
Correlation analysis. Linear correlation analysis between the amount of mean ppMEP changes during iTMS1.5 ms and iTMSadj [%]. Subjects that experienced the most prominent ppMEP changes during iTMS1.5 ms also had the largest changes in ppMEP during iTMSadj (r = 0.726; p = 0.005). However, those subjects with only little changes after iTMS1.5 ms were those that showed strong further facilitation after adjusting for the individual I1-wave peak latency (iTMSadj).
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