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The role of pulse shape in motor cortex transcranial magnetic stimulation using full-sine stimuli

A full-sine (biphasic) pulse waveform is most commonly used for repetitive transcranial magnetic stimulation (TMS), but little is known about how variations in duration or amplitude of distinct pulse segments influence the effectiveness of a single TMS pulse to elicit a corticomotor response. Using a novel TMS device, we systematically varied the configuration of full-sine pulses to assess the impact of configuration changes on resting motor threshold (RMT) as measure of stimulation effectiveness with single-pulse TMS of the non-dominant motor hand area (M1). In young healthy volunteers, we (i) compared monophasic, half-sine, and full-sine pulses, (ii) applied two-segment pulses consisting of two identical half-sines, and (iii) manipulated amplitude, duration, and current direction of the first or second full-sine pulse half-segments. RMT was significantly higher using half-sine or monophasic pulses compared with full-sine. Pulses combining two half-sines of identical polarity and duration were also characterized by higher RMT than fullsine stimuli resulting. For full-sine stimuli, decreasing the amplitude of the halfsegment inducing posterior-anterior oriented current in M1 resulted in considerably higher RMT, whereas varying the amplitude of the half-segment inducing anterior-posterior current had a smaller effect. These findings provide direct experimental evidence that the pulse segment inducing a posterior anterior directed current in M1 contributes most to corticospinal pathway excitation. Preferential excitation of neuronal target cells in the posterior-anterior segment or targeting of different neuronal structures by the two half-segments can explain this result. Thus, our findings help understanding the mechanisms of neural stimulation by full-sine TMS.

Identiferoai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:15-qucosa-158142
Date17 December 2014
CreatorsDelvendahl, Igor, Gattinger, Norbert, Berger, Thomas, Gleich, Bernhard, Siebner, Hartwig R., Mall, Volker
ContributorsUniversität Leipzig, Medizinische Fakultät, Technische Universität München, Zentralinstitut für Medizintechnik, Universität Freiburg, Universitätsklinikum, Københavns Universitet, Hvidovre Hospital, Technische Universität München, Kinderklinik, Public Library of Science,
PublisherUniversitätsbibliothek Leipzig
Source SetsHochschulschriftenserver (HSSS) der SLUB Dresden
LanguageEnglish
Detected LanguageEnglish
Typedoc-type:article
Formatapplication/pdf
SourcePLoS ONE 9(12): e115247. doi:10.1371/journal.pone.0115247

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