Modulation of the gait pattern during split-belt locomotion after lateral spinal cord hemisection in adult cats

Most previous studies investigated the recovery of locomotion in animals and people with incomplete spinal cord injury (SCI) during relatively simple tasks (e.g. walking in a straight line on a horizontal surface or on a treadmill). We know less about the recovery of locomotion after incomplete SCI in left-right asymmetric conditions, such as turning or stepping along circular trajectories. To investigate this, we collected kinematic and electromyography data during split-belt locomotion at different left-right speed differences before and after a right thoracic lateral spinal cord hemisection in nine adult cats. After hemisection, although cats still performed split-belt locomotion, we observed several changes in the gait pattern compared to the intact state at early (1-2 weeks) and late (7-8 weeks) time points. Cats with larger lesions showed new coordination patterns between the fore- and hindlimbs, with the forelimbs taking more steps. Despite this change in fore-hind coordination, cats maintained consistent phasing between the fore- and hindlimbs. Adjustments in cycle and phase (stance, swing) durations between the slow and fast sides allowed animals to maintain 1:1 left-right coordination. Periods of triple support involving the right (ipsilesional) hindlimb decreased in favor of quad support and triple support involving the other limbs. Step and stride lengths decreased with concurrent changes in the right fore- and hindlimbs, possibly to avoid interference. The above adjustments in the gait pattern allowed cats to retain the ability to locomote in asymmetric conditions after incomplete SCI. We discuss potential plastic neuromechanical mechanisms involved in locomotor recovery in these conditions.

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