Intraspinal micro stimulation generates locomotor-like and feedback-controlled movements

Area of Science:

• Neuroscience
• Biomedical Engineering
• Motor Control

Background:

• Spinal cord injuries, head trauma, and stroke impair motor function.
• Intraspinal microstimulation (ISMS) is a potential therapeutic approach.
• Restoring hindlimb locomotion and controlled movement is a key challenge.

Purpose of the Study:

• To investigate if spinal cord microstimulation can induce locomotor-like stepping in hindlimbs.
• To determine if ISMS can create feedback-controlled movements.
• To identify optimal electrode locations for eliciting locomotion.

Main Methods:

• Implanted 24 microwires into the lumbosacral spinal cord of adult cats under anesthesia.
• Utilized a sling to suspend cats, allowing hindlimb movement.
• Applied electrical stimulation through varying electrode configurations.
• Tested feedback control by modulating stimulus amplitude based on sensor feedback.

Main Results:

• Achieved bilateral, alternating hindlimb stepping with adequate stride length and foot clearance.
• Demonstrated sufficient ground reaction force for load-bearing.
• Successfully generated feedback-controlled foot movements that tracked target displacements.
• Found that stimulation near lamina IX yielded the most suitable locomotor movements.

Conclusions:

• Microstimulation of the mammalian spinal cord can generate near-normal locomotor-like stepping.
• Feedback-controlled movements of the hindlimbs are achievable via ISMS.
• Electrode placement, particularly near lamina IX, is critical for successful ISMS-induced locomotion.
• ISMS shows promise for restoring motor function after neurological injury.