Bogard Alysha T, Hembree Thomas G, Pollet Aviva K, Smith Andrew C, Ryder Stephanie C, Marzloff George, Tan Andrew Q
Sensorimotor Recovery and Neuroplasticity Lab at the University of Colorado, Boulder, Dept. of Integrative Physiology, 80309, USA.
University of Colorado School of Medicine, Dept. of Physical Medicine and Rehabilitation, Aurora, 80045, USA.
Res Sq. 2024 Apr 24:rs.3.rs-4259378. doi: 10.21203/rs.3.rs-4259378/v1.
Acute intermittent hypoxia (AIH) enhances human motor function after incomplete spinal cord injury. Although the underlying mechanisms in humans are unknown, emerging evidence indicates that AIH facilitates corticospinal excitability to the upper limb. However, the functional relevance of this plasticity remains unexplored, and it is unclear whether similar plasticity can be induced for lower limb motor areas. We recently demonstrated that AIH improves motor learning and metabolic efficiency during split-belt walking. Thus, we hypothesized that AIH increases lower limb excitability and that these enhancements would predict the magnitude of motor learning and the corresponding reductions in net metabolic power. We assessed tibialis anterior (TA) excitability using transcranial magnetic stimulation and quantified changes in spatiotemporal asymmetries and net metabolic power in response to split-belt speed perturbations. We show that AIH enhances TA excitability, and that the magnitude of this facilitation positively correlates with greater spatiotemporal adaptation. Notably, we demonstrate a novel association between increased excitability and reduced net metabolic power during motor learning and savings. Together, our results suggest that AIH-induced gains in excitability predict both the magnitude of motor learning and the associated metabolic efficiency. Determining indices of AIH-induced improvements in motor performance is critical for optimizing its therapeutic reach.
急性间歇性低氧（AIH）可增强不完全性脊髓损伤后人的运动功能。尽管其在人类中的潜在机制尚不清楚，但新出现的证据表明，AIH可促进皮质脊髓对上肢的兴奋性。然而，这种可塑性的功能相关性仍未得到探索，并且尚不清楚下肢运动区域是否能诱导出类似的可塑性。我们最近证明，AIH可改善分带步行过程中的运动学习和代谢效率。因此，我们假设AIH会增加下肢的兴奋性，并且这些增强作用将预测运动学习的程度以及净代谢功率的相应降低。我们使用经颅磁刺激评估胫前肌（TA）的兴奋性，并量化了响应分带速度扰动时时空不对称性和净代谢功率的变化。我们发现AIH可增强TA的兴奋性，并且这种促进作用的程度与更大的时空适应性呈正相关。值得注意的是，我们证明了在运动学习和节省过程中，兴奋性增加与净代谢功率降低之间存在新的关联。总之，我们的结果表明，AIH诱导的兴奋性增加可预测运动学习的程度以及相关的代谢效率。确定AIH诱导的运动表现改善指标对于优化其治疗效果至关重要。
