Guay-Hottin, R. | bioRxiv Science

bioRxiv2025

Combining cortical and spinal stimulation maximizes improvement of gait after spinal cord injury

Most spinal cord injuries (SCI) spare descending motor pathways and sublesional networks, which can be activated through motor cortex and spinal cord stimulation to mitigate locomotor deficits. However, the potential synergy between cortical and spinal stimulation as a neuroprosthetic intervention remains unknown. Here, we first investigated phase-locked electrical stimulation of the motor cortex and lumbar spinal cord at 40 Hz in a rat model of unilateral SCI. Combining cortical and lumbar stimulation around the anticipated lift synergistically enhanced leg movements. When integrated into rehabilitation training, cortical stimulation proved essential for recovery of skilled locomotion. As a further refinement, we next investigated the effects of high-frequency (330 Hz) lumbar and sacral stimulation combined with cortical stimulation. Timely integration during the swing phase showed that cortical and rostral lumbar stimulations enhance the initial and mid-swing phases, while sacral stimulation improves extension velocity in the late swing. These findings indicate that supraspinal and sublesional neuromodulation offer complementary neuroprosthetic effects in targeted SCI gait rehabilitation. HighlightsO_LICortical and spinal stimulations summate motor outputs via distinct pathways. C_LIO_LIEach improves gait post-SCI, but combined stimulation maximizes gait improvement. C_LIO_LIIntegrating cortico-spinal stimulation into rehabilitation promotes lasting recovery. C_LIO_LIEES capabilities extended using high-frequency lumbosacral protocols. C_LI

neuroscience↗

bioRxiv2024

Modulation of leg trajectory by transcranial magnetic stimulation during walking

The primary motor cortex is involved in initiation and adaptive control of locomotion. However, the role of the motor cortex in controlling gait trajectories remains unclear. In animals, cortical neuromodulation allows for precise control of step height. We hypothesized that a similar control framework applies to humans, whereby cortical stimulation would primarily increase foot elevation. Transcranial magnetic stimulation (TMS) was applied over the motor cortex to assess the involvement of the corticospinal tract over the limb trajectory during human walking. Eight healthy adults (aged 20-32 years) participated in treadmill walking at 1.5 km/h. TMS was applied over the left motor cortex at an intensity of 120% of the threshold to elicit a dorsiflexion of the right ankle during the swing phase of gait. Electromyographic (EMG) measurements and three-dimensional (3D) lower limb kinematics were collected. When delivered during the early swing phase, TMS led to a significant increase in the maximum height of the right toe by a mean of 40.7% {+/-} 14.9% (25.6mm {+/-} 9.4 mm, p = 0.0352) and knee height by 57.8%{+/-} 16.8%; (32mm {+/-} 9.3 mm; p = 0.008) across participants. These findings indicate that TMS can influence limb trajectory during walking, highlighting its potential as a tool for studying cortical control of locomotion.

neuroscience↗