Phase-targeted peripheral stimulation modulates cortical sensorimotor responses

The oscillatory brain state shapes how peripheral inputs are processed within sensorimotor circuits, but the cortical signatures of EEG phase-targeted peripheral stimulation across frequencies remain incompletely characterized. Here, we delivered single-pulse neuromuscular electrical stimulation (NMES) to the right extensor digitorum communis muscle, while triggering stimulation timing in real time to predefined EEG phase targets. In nineteen healthy young adults, we systematically varied ten different target frequencies (4 to 40 Hz) and eight phase bins, yielding stimulation-evoked potentials with canonical components (P30, N60, N120, P190). Using a two-stage analysis strategy, we first defined component-specific regions of interest from stimulation-evoked responses independent of phase and frequency, then tested phase dependence via cosine-model fits across the resulting component-by-frequency search space. The clearest exploratory candidate pattern was observed for the long-latency P190 component at 16 Hz, with maximal fitted responses for NMES triggered at 45°, corresponding to the early rising segment of the oscillatory cycle. These results suggest that the timing of peripheral stimulation relative to ongoing EEG phase may influence late cortical sensorimotor responses, with the strongest candidate effect expressed in late evoked activity consistent with higher-order sensorimotor processing.