Probing intrahemispheric interactions with a novel dual-site TMS setup

• Published in: Clinical neurophysiology Vol. 158; pp. 180 - 195
• Main Authors: Hehl, Melina, Van Malderen, Shanti, Geraerts, Marc, Meesen, Raf L.J., Rothwell, John C., Swinnen, Stephan P., Cuypers, Koen
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.02.2024
• Subjects: Dorsal premotor cortex (PMd); Dual-site TMS (dsTMS); Effective functional connectivity; Intrahemispheric interaction; Neurology; Transcranial magnetic stimulation (TMS); A; M1; PMd; I; FDI; DP; L; P; default; R; S; Effective functional connectivity; E-field; Dorsal premotor cortex (PMd); PMv; rMT; SICI; SP; EMG; ISI; mTMS; DLPFC; ppTMS; MSO; LMM; Transcranial magnetic stimulation (TMS); CS; Dual-site TMS (dsTMS); SimNIBS; spTMS; MEP; RMS; TMS; Intrahemispheric interaction; dsTMS; reversed; S1; TS; dual-site transcranial magnetic stimulation; resting motor threshold; motor-evoked potential; paired-pulse transcranial magnetic stimulation; short-interval intracortical inhibition; conditioning stimulus; ventral premotor cortex; transcranial magnetic stimulation; dorsolateral prefrontal cortex; inter-stimulus interval; primary somatosensory cortex; stimuli set to induce P–A-directed currents (second phase of a biphasic pulse); posterior; Simulation of Non-Invasive Brain Stimulation; left; single pulse; root mean square; double-pulse; anterior; single-pulse transcranial magnetic stimulation; primary motor cortex; inferior; first dorsal interosseus muscle; right; test stimulus; electrical field; maximal stimulator output; superior; stimuli set to induce A–P-directed currents (second phase of a biphasic pulse); electromyography; multi-locus transcranial magnetic stimulation; linear mixed model; dorsal premotor cortex
• ISSN: 1388-2457; 1872-8952; 1872-8952
• DOI: 10.1016/j.clinph.2023.12.128

•We developed a novel dual-site TMS setup to stimulate two adjacent brain regions.•It is subject to fewer technical and spatial limitations than previous attempts.•This enables more accurate and repeatable targeting of brain regions. Using dual-site transcranial magnetic stimulation (dsTMS), the effective connectivity between the primary motor cortex (M1) and adjacent brain areas such as the dorsal premotor cortex (PMd) can be investigated. However, stimulating two brain regions in close proximity (e.g., ±2.3 cm for intrahemispheric PMd–M1) is subject to considerable spatial restrictions that potentially can be overcome by combining two standard figure-of-eight coils in a novel dsTMS setup. After a technical evaluation of its induced electric fields, the dsTMS setup was tested in vivo (n = 23) by applying a short-interval intracortical inhibition (SICI) protocol. Additionally, the intrahemispheric PMd–M1 interaction was probed. E-field modelling was performed using SimNIBS. The technical evaluation yielded no major alterations of the induced electric fields due to coil overlap. In vivo, the setup reliably elicited SICI. Investigating intrahemispheric PMd–M1 interactions was feasible (inter-stimulus interval 6 ms), resulting in modulation of M1 output. The presented dsTMS setup provides a novel way to stimulate two adjacent brain regions with fewer technical and spatial limitations than previous attempts. This dsTMS setup enables more accurate and repeatable targeting of brain regions in close proximity and can facilitate innovation in the field of effective connectivity.