Spinal Cord Stimulation Improves Deceleration Phase Control during Targeted Reaching Post-Stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Chronic post-stroke hemiparesis often impairs upper-limb function.
• Cervical spinal cord stimulation (SCS) shows promise in improving motor control.
• The precise mechanisms by which SCS affects arm movement control post-stroke are not fully understood.

Purpose of the Study:

• To quantitatively characterize the effects of SCS on arm movement control in individuals with post-stroke hemiparesis.
• To investigate the underlying neuromotor control strategies influenced by SCS.
• To explore the potential of a proportional-derivative (PD) control model as a biomarker for SCS parameter selection.

Main Methods:

• Utilized a proportional-derivative (PD) control model to analyze planar reaching data.
• Collected data from 12 healthy individuals and 5 participants with chronic post-stroke hemiparesis.
• Compared model parameters between healthy controls, stroke participants, and stroke participants receiving SCS.

Main Results:

• The PD model accurately described reaching movements, with proportional gains for acceleration and derivative gains for deceleration.
• In healthy individuals, a balanced interplay between position and velocity-dependent torques was observed.
• SCS partially normalized the altered balance in stroke participants, particularly affecting the velocity-dependent term, suggesting a role in suppressing antagonistic muscle hyperexcitability.

Conclusions:

• SCS influences arm movement control post-stroke, with significant effects on the deceleration phase.
• Findings suggest SCS may primarily act by suppressing antagonistic muscle hyperexcitability rather than solely enhancing agonistic muscle drive.
• PD controller model parameters show frequency-dependent effects, indicating their potential as biomarkers for optimizing SCS parameters in stroke rehabilitation.