Differential modulation of sensorimotor alpha rhythms by motor imagery, electrical stimulation, and mirror visual...

Peripheral nerve reconstruction often requires prolonged rehabilitation to restore sensorimotor function. Motor imagery (MI), electrical stimulation (ES), and mirror visual feedback (MVF) are commonly used rehabilitation strategies; however, their comparative effects on cortical oscillatory dynamics during early neural recovery remain unclear. This study investigated EEG sensorimotor rhythm modulation during MI, ES, and ES combined with MVF in individuals who had undergone upper limb peripheral nerve reconstruction.

Eleven patients, within six months after peripheral nerve reconstruction, and twenty-one age-matched healthy participants were recruited. Electroencephalography was recorded during the resting state and three independent task conditions: MI, ES with sham MVF, and ES combined with MVF. Relative power (RP) and baseline-normalized changes in relative power (ΔRP) in EEG spectral bands were calculated to characterize task-related modulation of sensorimotor rhythms. To control for multiple condition contrasts, p values were adjusted using the Benjamini-Hochberg false discovery rate (FDR-adjusted) procedure within each frequency band and group.

Task-related modulation was most pronounced in the alpha band. In healthy participants, alpha RP significantly decreased during all task conditions compared with the resting state (all FDR-adjusted p < 0.001). In contrast, patients showed significant alpha RP suppression during ES and MVF (FDR-adjusted p < 0.001 and p = 0.002, respectively), whereas MI alone showed less evident alpha RP suppression and did not reach statistical significance after FDR correction (FDR-adjusted p = 0.078). Greater alpha band ΔRP during MVF than MI was observed in healthy participants (FDR-adjusted p = 0.009), whereas the corresponding contrast did not remain significant in patients after FDR correction (FDR-adjusted p = 0.090). Modulation of beta rhythms was limited in both groups (all FDR-adjusted p > 0.05).

These findings suggest that alpha modulation during MI was less evident in patients following peripheral nerve reconstruction. However, given the limited sample size, the non-significant MI finding should be interpreted cautiously. In contrast, ES-based interventions, particularly when combined with MVF, were associated with greater sensorimotor rhythm modulation, supporting the potential role of multimodal rehabilitation strategies in facilitating cortical reorganization during early neural recovery after peripheral nerve repair.