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Published on: January 20, 2012
Rostro-caudal TMS mapping of immediate transcranial evoked potentials reveals a pericentral crescendo-decrescendo
Marten Nuyts1, Mikkel Malling Beck2, Agata Banach2
1Danish Research Centre for Magnetic Resonance, Department of Radiology and Nuclear Medicine, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark, Kettegård Allé 30, 2650 Hvidovre, Denmark; REVAL - Rehabilitation Research Center, Faculty of Rehabilitation Sciences, University of Hasselt, Diepenbeek, Belgium.
Single-pulse transcranial magnetic stimulation (TMS) elicits immediate transcranial evoked potentials (iTEPs) in the sensorimotor cortex. These iTEPs and motor-evoked potentials (MEPs) show similar spatial patterns, suggesting overlapping but distinct neuronal origins.
Area of Science:
- Neuroscience
- Electrophysiology
- Transcranial Magnetic Stimulation (TMS)
Background:
- Single-pulse TMS of the primary sensorimotor hand area (SM1HAND) elicits immediate transcranial evoked potentials (iTEPs) within 2-8 ms.
- iTEPs feature high-frequency peaks on a slow positive wave.
- This study compares the spatial expression of iTEPs and motor-evoked potentials (MEPs).
Purpose of the Study:
- To characterize the rostro-caudal expression of iTEPs using a linear TMS-EEG mapping approach.
- To compare iTEP expression patterns with those of MEPs.
Main Methods:
- 15 healthy young volunteers underwent TMS-EEG.
- Single biphasic TMS pulses were applied over six sites along the rostro-caudal axis of the left SM1HAND.
- Site-specific iTEP and MEP responses were analyzed.
Main Results:
- iTEP magnitude decreased both rostrally and caudally from the SM1HAND hotspot.
- MEPs showed a similar rostro-caudal crescendo-decrescendo pattern.
- Normalized iTEP amplitudes decayed less rapidly than MEPs at the first postcentral site.
Conclusions:
- Pericentral iTEPs may reflect direct, synchronized excitation of cortical pyramidal tract neurons.
- Similar, yet non-identical, spatial patterns suggest iTEPs and MEPs originate from overlapping but distinct neuronal populations.
