Neural Noise- EEG–TMS can be used to predict excitability of the motor cortex leg representation.1
- Combined EEG–TMS is a direct electrophysiology and motor mapping method relevant to interfaces and TMS applications.1 1
Weekly enrichment (2026-07-20)
- Published in Clinical Neurophysiology (2026, Kirchhoff et al.), this is the first EEG-TMS study to predict corticospinal excitability of the motor cortex (M1) leg representation, extending prior work that had been limited to the hand representation.2
- Cohort: 16 healthy subjects analyzed (14 female, 2 male, age 24 ± 2 years) after screening 60 and retaining 20; single-pulse navigated TMS targeted the tibialis anterior (TA) hotspot, in left M1 for 10 participants and right M1 for 6.23
- Method: navigated single-pulse TMS with simultaneous EEG and EMG; 1,000 trials per subject across four blocks of 250 pulses, with stimulation intensity set to the input-output curve inflection point and an inter-stimulus interval of 3 ± 0.2 s.2
- EEG was Hjorth/Laplacian-filtered over sensorimotor cortex (C1/C2 and C3/C4) using individualized frequency bands (mu 8-12.5 Hz, beta 13-30 Hz), with mu-phase estimated via PHASTIMATE.2
- Result: power in the high-gamma band correlated positively, and beta-band power negatively, with MEP amplitude.23
- Mu-phase alone had no main effect, but a significant mu-power × mu-phase interaction emerged: with high mu-power the largest MEPs occurred at the early peak, while with low mu-power the largest MEPs occurred at the late peak.23
- Data quality: 18.14% of trials were rejected (EMG pre-innervation, absent MEP, scalp-muscle contamination, or noisy EEG); mu-band signal-to-noise was 6.7 dB (C3/C4) and 5.5 dB (C1/C2).2
- Implication: these pre-stimulus EEG signatures could enable brain-state-dependent TMS of the leg representation for treating gait or balance disorders and supporting gait neurorehabilitation after stroke.23