Spinal Cord Injury-Induced Changes in Encoding and Decoding of Bipedal Walking by Motor Cortical Ensembles

Abstract

Recent studies have shown that motor recovery following spinal cord injury (SCI) is task-specific. However, most consequential conclusions about locomotor functional recovery from SCI have been derived from quadrupedal locomotion paradigms. In this study, two monkeys were trained to perform a bipedal walking task, mimicking human walking, before and after T8 spinal cord hemisection. Importantly, there is no pharmacological therapy with nerve growth factor for monkeys after SCI; thus, in this study, the changes that occurred in the brain were spontaneous. The impairment of locomotion on the ipsilateral side was more severe than that on the contralateral side. We used information theory to analyze single-cell activity from the left primary motor cortex (M1), and results show that neuronal populations in the unilateral primary motor cortex gradually conveyed more information about the bilateral hindlimb muscle activities during the training of bipedal walking after SCI. We further demonstrated that, after SCI, progressively expanded information from the neuronal population reconstructed more accurate control of muscle activity. These results suggest that, after SCI, the unilateral primary motor cortex could gradually regain control of bilateral coordination and motor recovery and in turn enhance the performance of brain–machine interfaces.

Non-human primate models and systems for gait and neurophysiological analysis

“…Among them, Frame DIAS (21 studies: e.g., Mori et al, 2006;Higurashi et al, 2010;Goto et al, 2021), Simi Motion (five studies: Fitzsimmons et al, 2009;Capogrosso et al, 2016;Vouga et al, 2017;Tseng et al, 2019;Xing et al, 2019), Peak Motus software (four studies: Courtine et al, 2005a,b;Larson and Demes, 2011;Demes and O'Neill, 2013), and Xcitex (seven studies: e.g., O'Neill et al, 2015;Thompson et al, 2018;Young and Chadwell, 2020) were commonly used (n = 37; 52.1%). The remaining 34 studies used self-written programs based on development platforms, such as MATLAB (Reghem et al, 2013(Reghem et al, , 2014Pontzer et al, 2014;Dunham et al, 2018) and C++ (Peikon et al, 2009), or manually observed and analyzed videos or photos to obtain spatial-temporal parameters (Kimura, 2000;Nakano, 2002;Ma et al, 2016;Hu et al, 2021).…”

“…NHP studies of intracortical neural recordings or BCI were based on home-made (e.g., HermesB) or commercial neural recording systems (e.g., Blackrock Microsystems, Salt Lake City, UT, USA; FHC Inc., Bowdoin, ME, USA). EMG studies employed implantable electrodes (Yin et al, 2014;Hu et al, 2021;Shitara et al, 2022b) or surface EMG sensors (Nakano, 2002;Goetz et al, 2012;Wei et al, 2019). Ma et al (2016) adopted MEP and SSEP to evaluate spinal cord function electrophysiologically in NHP models.…”