Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.
Elsass Foundation, Charlottenlund, Denmark.
J Neurophysiol. 2024 Oct 1;132(4):1126-1141. doi: 10.1152/jn.00466.2023. Epub 2024 Aug 28.
Walking in natural environments requires visually guided modifications, which can be more challenging when involving sideways steps rather than longer steps. This exploratory study investigated whether these two types of modifications involve different changes in the central drive to spinal motor neurons of leg muscles. Fifteen adults [age: 36 ± 6 (SD) years] walked on a treadmill (4 km/h) while observing a screen displaying the real-time position of their toes. At the beginning of the swing phase, a visual target appeared in front (forward) or medial-lateral (sideways) of the ground contact in random step cycles (approximately every third step). We measured three-dimensional kinematics and electromyographic activity from leg muscles bilaterally. Intermuscular coherence was calculated in the alpha (5-15 Hz), beta (15-30 Hz), and gamma bands (30-45 Hz) approximately 230 ms before and after ground contact in control and target steps. Results showed that adjustments toward sideways targets were associated with significantly higher error, lower foot lift, and higher cocontraction between antagonist ankle muscles. Movements toward sideways targets were associated with larger beta-band soleus (SOL): medial gastrocnemius (MG) coherence and a more narrow and larger peak of synchronization in the cumulant density before ground contact. In contrast, movements toward forward targets showed no significant differences in coherence or synchronization compared with control steps. Larger SOL:MG beta-band coherence and short-term synchronization were observed during sideways, but not forward, gait modifications. This suggests that visually guided gait modifications may involve differences in the central drive to spinal ankle motor neurons dependent on the level of task difficulty. This exploratory study suggests a specific and temporally restricted increase of central (likely corticospinal) drive to ankle muscles in relation to visually guided gait modifications. The findings indicate that a high level of visual attention to control the position of the ankle joint precisely before ground contact may involve increased central drive to ankle muscles. These findings are important for understanding the neural mechanisms underlying visually guided gait and may help develop rehabilitation interventions.
在自然环境中行走需要视觉引导的修正，而涉及横向跨步而不是更长的跨步时，这种修正可能更具挑战性。这项探索性研究调查了这两种类型的修正是否涉及腿部肌肉脊髓运动神经元的中枢驱动的不同变化。15 名成年人[年龄：36 ± 6（SD）岁]在跑步机上行走（4 公里/小时），同时观察屏幕上显示的脚趾实时位置。在摆动阶段开始时，一个视觉目标出现在地面接触点的前方（向前）或内侧-外侧（横向）随机步周期（大约每三步一次）。我们测量了双腿的三维运动学和肌电图活动。在控制和目标步中，大约在地面接触前 230 毫秒，在 alpha（5-15 Hz）、beta（15-30 Hz）和 gamma 波段（30-45 Hz）计算了肌肉间相干性。结果表明，向横向目标的调整与明显更高的误差、更低的足抬高和拮抗踝肌之间更高的共收缩有关。向横向目标的运动与更大的 beta 波段比目鱼肌（SOL）：内侧腓肠肌（MG）相干性以及在 cumulant 密度之前接触地面之前更窄和更大的同步峰值相关。相比之下，与控制步相比，向向前目标的运动在相干性或同步性方面没有显示出显著差异。在向横向而不是向前的步态修正过程中观察到更大的 SOL：MG beta 波段相干性和短期同步性。这表明，视觉引导的步态修正可能涉及到依赖于任务难度水平的脊髓踝运动神经元的中枢驱动的差异。这项探索性研究表明，在向地面接触之前，踝关节位置的精确视觉注意力可能涉及到对踝肌的中枢驱动增加。这些发现对于理解视觉引导步态的神经机制很重要，并可能有助于开发康复干预措施。
