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Journal Article

The number of full-sine cycles per pulse influences the efficacy of multicycle transcranial magnetic stimulation

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Citation

Pechmann, A., Delvendahl, I., Bergmann, T. O., Ritter, C., Hartwigsen, G., Gleich, B., et al. (2012). The number of full-sine cycles per pulse influences the efficacy of multicycle transcranial magnetic stimulation. Brain Stimulation, 5(2), 148-154. doi:10.1016/j.brs.2011.02.006.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0028-D5AD-C
Abstract
Background

Previous studies have shown that the efficacy of transcranial magnetic stimulation (TMS) to excite corticospinal neurons depends on pulse waveform.
Objective/Hypotheses

In this study, we examined whether the effectiveness of polyphasic TMS can be increased by using a pulse profile that consists of multiple sine cycles.
Methods

In eight subjects, single-pulse TMS was applied to the left primary motor hand area through a round coil attached to a stimulator device that generated polyphasic pulses consisting of one to six full-sine cycles with a cycle length of 86 μs. In different blocks, we varied the number of sine cycles per pulse and recorded the motor-evoked potential (MEP) from the right first dorsal interosseus muscle. For each stimulus type, we determined resting motor threshold (RMT), stimulus-response curve (SRC), and mean MEP amplitude evoked at maximal stimulator output to assess the efficacy of stimulation.
Results

Multicycle pulses were more effective than a single full-sine cycle in exciting corticospinal neurons. TMS with multicycle pulses resulted in lower RMT, larger MEP amplitudes at maximal stimulator output and a steeper slope of the SRC relative to a TMS pulse consisting of a single-sine cycle. The increase in efficacy was already evident when two full-sine cycles were used and did not increase further by adding more cycles to the TMS pulse.
Conclusions

Increasing the number of full-sine cycles per pulse can improve the efficacy of TMS to excite corticospinal neurons, but there is no simple linear relationship between the number of cycles and TMS efficacy.