Spatial activation of motor evoked potentials depends on paired-pulse transcranial magnetic stimulation orientation and intensity

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Authors

Date

2026-02

Department

Department of Neuroscience and Biomedical Engineering

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Mcode

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Language

en

Pages

10

Series

Clinical Neurophysiology, Volume 183, pp. 1-10

Abstract

Objective To investigate how stimulus orientation, intensity, and interstimulus interval (ISI) in paired-pulse transcranial magnetic stimulation (TMS) influence the spatial activation of motor evoked potentials (MEPs) in forearm flexor muscles. Methods Paired-pulse paradigms were applied to the motor cortex using multi-coil TMS (mTMS) to control the stimulus parameters electronically without coil repositioning. MEP spatial activation was recorded with a high-density surface electromyography (HDsEMG) grid over the forearm muscles. Conditioning stimuli (CS) were delivered at anterior-to-medial (0°) and posterior-to-medial (90°) orientations and 70–90 % of resting motor threshold (rMT), followed by test stimuli (TS) at 0° and 110 % rMT. ISIs of 0.5 and 8 ms probed neuronal refractoriness and intracortical facilitation, respectively. Results MEPs were facilitated at 8-ms and suppressed at 0.5-ms ISI. At 0.5 ms, changing CS orientation from 0° to 90° reduced suppression. Increasing CS intensity shifted activation centroids medially in most cases. Centroids were more medial at 8 ms and more lateral at 0.5 ms. Conclusions TMS pulse orientation, intensity, and ISI systematically affect the magnitude and spatial activation of forearm muscles. Significance Our findings highlight the utility of mTMS–HDsEMG in probing neurophysiological mechanisms of corticomotor control with important diagnostic and therapeutic clinical implications.

Description

| openaire: EC/H2020/810377/EU//ConnectToBrain

Keywords

Spatial muscle recruitment, Muscle imaging, Short-interval intracortical inhibition, Intracortical facilitation, Paired-pulse stimulation, Multi-coil TMS, Motor control

Other note

DOI

10.1016/j.clinph.2025.2111477

Citation

Parvin, S, Juurakko, J, Sinisalo, H, Cerone, G L, Botter, A, Ilmoniemi, R, Piitulainen, H & Souza, V 2026, 'Spatial activation of motor evoked potentials depends on paired-pulse transcranial magnetic stimulation orientation and intensity', Clinical Neurophysiology, vol. 183, 2111477, pp. 1-10. https://doi.org/10.1016/j.clinph.2025.2111477

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https://urn.fi/URN:NBN:fi:aalto-202512299573

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[article-cris] Perustieteiden korkeakoulu / SCI