Intraspinal microstimulation produces over-ground walking in anesthetized cats

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Science

Background:

• Spinal cord injury (SCI) results in significant loss of motor, sensory, and autonomic functions.
• Restoring motor function after SCI is a major challenge in neurorehabilitation.
• Activating intrinsic spinal locomotor networks offers a potential therapeutic strategy.

Purpose of the Study:

• To investigate the efficacy of intraspinal microstimulation (ISMS) for enabling long-distance over-ground walking.
• To determine if ISMS can activate spinal networks to produce functional locomotion after SCI.
• To assess the feasibility of ISMS for future clinical applications in SCI recovery.

Main Methods:

• ISMS was applied using 16 fine penetrating electrodes targeting the ventral horn of the lumbar enlargement in adult cats.
• A physiologically-based control strategy delivered patterned stimulation to evoke walking movements.
• Limb kinematics and forces were recorded during over-ground walking on an instrumented walkway.

Main Results:

• ISMS produced bilaterally coordinated and functional over-ground walking with low current amplitudes (<100 μA).
• Three cats achieved cumulative walking distances of 609–835 m, demonstrating sustained locomotion.
• The stimulation evoked appropriate supportive and propulsive forces, with hind leg support comparable to full body weight.

Conclusions:

• ISMS effectively activates inherent locomotor networks in the lumbosacral spinal cord.
• This method shows significant potential for restoring functional walking in individuals with SCI.
• A prototype implantable module demonstrated ISMS viability for future clinical translation.