Sub-Threshold Stochastic Vibration Improves Fingertip Tactile Sensitivity in Stroke Survivors and Healthy Adults, with Source-Localized EEG Evidence for Cortical Network Reorganization in Healthy Adults

Cutaneous sensation is vital for daily function and safety, yet it commonly declines with ageing and after neurological injury, with stroke survivors particularly affected. This study investigates whether sub-threshold stochastic (random) vibrations can enhance light-touch (cutaneous) sensation in healthy adults and stroke survivors and characterizes the associated changes in cortical functional connectivity (FC). Nineteen healthy participants and five stroke survivors took part. A custom device delivered sinusoidal and stochastic vibrations to the volar surface of the right middle fingertip. For each participant we first determined the detection threshold for stochastic vibration alone, then the threshold for a 30 Hz sinusoidal vibration, and then the threshold for that sinusoidal vibration combined with imperceptible stochastic noise fixed at 80% of the stochastic threshold; in ten healthy participants a super-threshold combination (120% of the stochastic threshold) was also tested. High-density (64-channel) electroencephalography (EEG) was recorded throughout for the healthy participants. Adding sub- threshold stochastic noise lowered the sinusoidal detection threshold in every participant tested and produced consistent reductions in all five stroke survivors; expressed as gains in sensitivity, individual improvements reached up to 19 times in healthy participants and up to 4 times in stroke survivors. Source- localized EEG showed that sub-threshold stochastic vibration significantly increased FC, most extensively in the alpha band, with prominent involvement of frontal regions (superior and rostral middle frontal cortices and anterior cingulate; cluster- based permutation p < 0.05), consistent with a noise-driven modulation of sensory and attentional networks. Super-threshold noise produced weaker, predominantly beta-band changes, in line with signal masking rather than resonance. These findings indicate that sub-threshold stochastic vibration lowers light-touch detection thresholds and reorganizes cortical connectivity in both healthy and stroke populations, and they support prioritizing cutaneous sensation in stochastic-resonance based neurorehabilitation for stroke survivors.