Preprint
The effect of pulse shape in theta-burst stimulation: monophasic vs biphasic TMS
- Abstract:
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Background Intermittent theta-burst stimulation (i)(TBS) is a transcranial magnetic stimulation (TMS) plasticity protocol. Conventionally, TBS is applied using biphasic pulses due to hardware limitations. However, monophasic pulses are hypothesised to recruit cortical neurons more selectively than biphasic pulses, thus yielding stronger plasticity effects. Monophasic and biphasic TBS can be generated using a custom-made pulse-width modulation-based TMS device (pTMS).
Objective Using pTMS, we tested the hypothesis that monophasic iTBS would induce greater plasticity effects than biphasic, measured as induced changes in motor corticospinal excitability.
Methods In a repeated-measures design, thirty healthy volunteers participated in three separate sessions, where monophasic and biphasic iTBS was applied to the primary motor cortex (M1 condition) or the vertex (control condition). Plasticity was quantified as changes in motor corticospinal excitability after versus before iTBS, by comparing peak-to-peak amplitudes of motor evoked potentials (MEP) measured at baseline and over 60 minutes after iTBS.
Results Both monophasic and biphasic M1 iTBS led to significant increases in MEP amplitude. As predicted, monophasic iTBS induced a significantly larger effect than biphasic iTBS (linear mixed effect model analysis: (χ2(1) = 7.48, p = 0.006), which persisted even after subtracting each individual’s control (vertex) condition data from the M1 conditions (χ2(1) = 5.48, p = 0.019).
Conclusions In this study, monophasic iTBS induced a stronger motor corticospinal excitability increase than biphasic within participants. This greater physiological effect suggests that monophasic iTBS may also have potential for greater functional impact, of interest for future fundamental and clinical applications of TBS.
- Publication status:
- Published
- Peer review status:
- Not peer reviewed
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(Preview, Pre-print, pdf, 740.9KB, Terms of use)
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- Preprint server copy:
- 10.1101/2023.03.06.531158
Authors
- Funder identifier:
- https://ror.org/029chgv08
- Grant:
- 203139/A/16/Z
- 203139/Z/16/Z
- 215451/Z/19/Z
- 224430/Z/21/Z
- Funder identifier:
- https://ror.org/0187kwz08
- Grant:
- NIHR203316
- Preprint server:
- bioRxiv
- Publication date:
- 2023-04-27
- DOI:
- EISSN:
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2692-8205
- Language:
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English
- Keywords:
- Pubs id:
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1331978
- Local pid:
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pubs:1331978
- Deposit date:
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2026-02-19
- ARK identifier:
Terms of use
- Copyright holder:
- Wendt et al
- Copyright date:
- 2023
- Rights statement:
- ©2023 The Authors. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license .
- Licence:
- CC Attribution (CC BY)
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