Modulation of proprioceptive feedback during functional electrical stimulation: an fMRI study

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Motor Control

Background:

• Functional electrical stimulation (FES) is a therapeutic tool in motor rehabilitation.
• Effective rehabilitation requires the central nervous system to integrate motor commands with sensory feedback.
• The role of sensory feedback in FES-assisted movement and its neural correlates remain unclear.

Purpose of the Study:

• To investigate the integration of motor commands and sensory feedback during FES-evoked and FES-assisted movements.
• To examine brain activation patterns associated with voluntary, FES-evoked, and FES-assisted movements under conditions with and without sensory feedback.

Main Methods:

• Healthy participants underwent functional magnetic resonance imaging (fMRI).
• Sensory feedback was blocked using a peripheral ischemic nerve block.
• Participants performed voluntary (VOL), FES-evoked (FES-ev), and FES-assisted (FES-as) movements during fMRI scans.

Main Results:

• Before nerve block, secondary somatosensory area (S2) activation was higher for FES-ev and FES-as compared to VOL movements.
• During nerve block, S2 activation decreased for FES-ev but not for FES-as or VOL movements.
• Nerve block reduced activation in primary somatosensory cortex and motor areas for FES, and in superior parietal lobule/precuneus for VOL movements.

Conclusions:

• FES-related S2 activation appears to be primarily a sensory response, not indicative of sensory-motor integration.
• FES-assisted movement may involve different neural processing compared to FES-evoked movement regarding sensory feedback.
• These findings have implications for optimizing FES-based rehabilitation strategies.