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bioRxiv · 10.1101/2025.02.14.638272

Rostro-caudal TMS mapping of immediate transcranial evoked potentials reveals a pericentral crescendo-decrescendo pattern

Nuyts, M.·Beck, M. M.·Banach, A.·Thielscher, A.·Meesen, R.·Tomasevic, L.·Siebner, H. R.·Christiansen, L.
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Abstract

BackgroundWe recently demonstrated that single-pulse TMS of the primary sensorimotor hand area (SM1HAND) elicits an immediate transcranial evoked potential (iTEP). This iTEP response appears within 2-7 ms post-TMS, featuring high-frequency peaks superimposed on a slow positive wave. Here, we used a linear TMS-EEG mapping approach to characterize the rostro-caudal iTEP expression and compared it to that of motor-evoked potentials (MEPs). MethodsIn 15 healthy young volunteers (9 females), we identified the iTEP hotspot in left SM1HAND. We applied single biphasic TMS pulses at an intensity of 110% of resting motor threshold over six cortical sites along a rostro-caudal axis (2 cm rostral to 3 cm caudal to the SM1HAND hotspot). We analyzed site-specific iTEP and MEP responses. ResultsiTEP magnitude decreased rostrally and caudally from the SM1HAND hotspot. MEPs exhibited a similar rostro-caudal crescendo-decrescendo pattern. While iTEP and MEP response profiles were similar, normalized iTEP amplitudes decayed less rapidly at the first postcentral site. DiscussionThese findings support the idea that pericentral iTEPs reflect a direct response signature of the pericentral cortex, possibly involving a synchronized TMS-induced excitation of cortical pyramidal tract neurons. Similar but non-identical rostro-caudal patterns suggest that iTEPs and MEPs may arise from overlapping but distinct neuronal populations.

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Nuyts, M., Beck, M. M., Banach, A., Thielscher, A., Meesen, R., Tomasevic, L., Siebner, H. R., Christiansen, L.. 2025-02-17. Rostro-caudal TMS mapping of immediate transcranial evoked potentials reveals a pericentral crescendo-decrescendo pattern. https://doi.org/10.1101/2025.02.14.638272

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