Spinal Reflex Modulation by a Sensory Neuroprosthesis During Gait in an Individual With Lower Limb Loss: Case Report

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Science

Background:

• Individuals with lower limb loss experience increased fall risk due to diminished sensory feedback from the missing limb.
• Plantar sensation is vital for maintaining balance and regulating spinal excitability during gait.

Purpose of the Study:

• To investigate how a sensory neuroprosthesis impacts the neural circuitry controlling locomotion.
• To determine if the sensory neuroprosthesis modulates spinal reflex pathways during gait in individuals with transtibial limb loss.

Main Methods:

• One participant with transtibial limb loss used an implanted sensory neuroprosthesis.
• The medial gastrocnemius H-reflex was measured during treadmill walking with the neuroprosthesis both active and inactive.
• H-reflex was evoked across different phases of the gait cycle.

Main Results:

• The H-reflex showed natural phase-dependent modulation during gait, increasing in late stance and decreasing in swing, even when the neuroprosthesis was inactive.
• Activation of the sensory neuroprosthesis facilitated the H-reflex across all gait phases.
• Neuroprosthesis activation normalized H-reflex modulation relative to biomechanical demands during gait.

Conclusions:

• Sensory feedback from the neuroprosthesis is integrated into the sensorimotor control of gait.
• The spinal reflex pathways process neuroprosthesis input in a context-appropriate manner, similar to natural sensory inputs.
• Sensory neuroprostheses hold promise for improving gait stability and reducing fall risk in individuals with lower limb loss.