Neuromodulatory effects of voluntary-motor-effort-driven wrist-hand robot in sensorimotor dynamics after stroke.

BACKGROUND

Voluntary motor effort (VME)-driven neuromuscular electrical stimulation (NMES)-robots have demonstrated superior rehabilitative efficacy in post-stroke wrist-hand motor restoration compared with purely mechanical systems. However, their neuromodulatory mechanisms remain unclear. This study aimed to investigate cortical responses elicited by an electromyography (EMG)-driven NMES-robot assisting wrist-hand movements in individuals with chronic stroke, and to evaluate robot-nervous system interactions, using EMG to capture VME.

METHODS

Cortical responses during wrist-hand extension were recorded in participants with chronic stroke (n = 18) and unimpaired controls (n = 20) using functional near-infrared spectroscopy (fNIRS). The EMG-driven NMES-robot delivered somatosensory stimulation with different combinations of mechanical stimulation (MS) to the targeted joints and NMES to the forearm muscles, with or without VME.

RESULTS

Combined MS and NMES co-stimulation activated wider cortical areas than MS or NMES alone in both groups. Compared with the unimpaired group, the stroke group exhibited greater ipsilesional activations in response to NMES (p < 0.05), while MS induced comparable activations in the contralateral hemisphere to the stimulated limb in both groups (p < 0.05). When VME was required, the stroke group exhibited wider contralesional involvement with MS only (p < 0.05) but reduced contralesional involvement during sole NMES (p < 0.05), compared to those in the co-stimulation. Additionally, the MS and NMES co-stimulation resulted in similar functional connectivity patterns between the stroke and unimpaired groups.

CONCLUSION

Combined mechano-electrical somatosensory co-stimulation with MS and NMES to the affected wrist-hand, when voluntary motor effort is generated from the residual muscles, could elicit extensive cortical activation approaching normal patterns.

TRIAL REGISTRATION: Chinese Clinical Trial Registry with the identifier ChiCTR2200057839.