2026/06/01 by Juliana Hougland, Timo Roine, Andreas Jooß +2 · 1 voice
Medicine · Neuroscience · Psychology · #Action Observation and Synchronization #Advanced Neuroimaging Techniques and Applications #Transcranial Magnetic Stimulation Studies
paper · doi:10.1002/hbm.70576
openalex publication_date 2026/06/01 · openalex created_date 2026/06/05 · openalex updated_date 2026/07/23
ABSTRACT The sensorimotor mu‐rhythm phase modulates corticospinal excitability, but mu‐phase effects on motor evoked potentials (MEPs) elicited with transcranial magnetic stimulation (TMS) vary substantially across individuals. Structural connectivity between primary motor cortex (M1) and primary somatosensory cortex (S1) may explain variability in effect strength. We examined whether S1–M1 microstructural connectivity relates to mu‐phase effect strength on MEP amplitudes. A total of 28 individuals completed diffusion magnetic resonance imaging (dMRI) and electroencephalography (EEG)–TMS. Fiber tractography between S1 and M1 was performed. Quantitative anisotropy and diffusion‐tensor imaging metrics including fractional anisotropy, radial diffusivity, and axial diffusivity were extracted from S1–M1 fibers, along with neurite orientation dispersion and density imaging metrics. Single‐pulse TMS was delivered to left M1. Mu‐phase was calculated from pre‐stimulus EEG, and MEP amplitudes were calculated from right‐hand muscles. Mu‐phase effect strength was quantified using a circular‐to‐linear correlation of mu‐phase and MEP amplitude. Spearman correlations assessed relationships between the dMRI measures and mu‐phase effect strength. Whole‐brain correlational tractography was performed to explore other tracts associated with mu‐phase effect strength. Higher S1–M1 quantitative anisotropy was associated with stronger mu‐phase effect on MEP amplitudes in both hemispheres (left: ρ = 0.384, p = 0.044; right: ρ = 0.409, p = 0.032). Exploratory whole‐brain correlations identified additional tracts relevant to mu‐phase effect strength. In conclusion, S1–M1 microstructural connectivity influences mu‐phase modulation of corticospinal excitability. Communication between S1–M1 is important for effective phase‐dependent TMS. dMRI could be used to predict individuals' potential for phase‐dependent TMS.