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Abstract
Measurement of the input–output (IO) curves of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) can be used to assess corticospinal excitability and motor recruitment. While IO curves have been used to study disease and pharmacology, few studies have compared the IO curves across the body. This study sought to characterize IO curve parameters across the dominant and non-dominant sides of upper and lower limbs in healthy participants. Laterality preferences were assessed in eight healthy participants and IO curves were measured bilaterally for the first dorsal interosseous (FDI), biceps brachii (BB), and tibialis anterior (TA) muscles. Results show that FDI has lower motor threshold than BB which is, in turn, lower than TA. In addition, both BB and TA have markedly shallower logarithmic IO curve slopes from small to large MEP responses than FDI. After normalizing these slopes by their midpoints to account for differences in motor thresholds, which could result from geometric factors such as the target depth, large differences in logarithmic slopes remain present between all three muscles. The differences in slopes between the muscles could not be explained by differences in normalized IO curve spreads, which relate to the extent of the cortical representation and were comparable across the muscles. The IO curve differences therefore suggest muscle-dependent variations in TMS-evoked recruitment across the primary motor cortex, which should be considered when utilizing TMS-evoked MEPs to study disease states and treatment effects.
Original language | English |
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Article number | 1310320 |
Journal | Frontiers in Human Neuroscience |
Volume | 18 |
DOIs | |
Publication status | Published - 7 Feb 2024 |
Bibliographical note
FundingThe author(s) declare financial support was received for the research, authorship, and/or publication of this article. The research reported in this publication was supported by the National Institute of Mental Health of the National Institutes of Health, US under Brain Initiative Awards Number RF1MH114253 and RF1MH114268, and by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 101027633. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.
Keywords
- transcranial magnetic stimulation
- TMS
- motor evoked potential
- MEP
- input–output curve
- IO curve
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- 1 Finished
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STIMUSURE - Simultaneous magnetic brain stimulation and measurement
Jensen, O. (Principal Investigator) & Koponen, L. (Co-Investigator)
18/08/21 → 15/02/24
Project: EU