Department of Physical Therapy, Movement and Rehabilitation Sciences, Northeastern University, Boston, MA 02115, USA.
UNC-NC State Joint Department of Biomedical Engineering, UNC-Chapel Hill, Chapel Hill, NC 27514, USA.
Neurosci Lett. 2021 Jan 18;742:135511. doi: 10.1016/j.neulet.2020.135511. Epub 2020 Nov 21.
Standing still and focusing on a visible target in front of us is a preamble to many coordinated behaviors (e.g., reaching an object). Hiding behind its apparent simplicity is a deep layering of texture at many scales. The task of standing still laces together activities at multiple scales: from ensuring that a few photoreceptors on the retina cover the target in the visual field on an extremely fine scale to synergies spanning the limbs and joints at smaller scales to the mechanical layout of the ground underfoot and optic flow in the visual field on the coarser scales. Here, we used multiscale probability density function (PDF) analysis to show that postural fluctuations exhibit similar statistical signatures of cascade dynamics as found in fluid flow. In participants asked to stand quietly, the oculomotor strain of visually fixating at different distances moderated postural cascade dynamics. Visually fixating at a comfortable viewing distance elicited posture with a similar cascade dynamics as posture with eyes closed. Greater viewing distances known to stabilize posture showed more diminished cascade dynamics. In contrast, nearest and farthest viewing distances requiring greater oculomotor strain to focus on targets elicited a dramatic strengthening of postural cascade dynamics, reflecting active postural adjustments. Critically, these findings suggest that vision stabilizes posture by reconfiguring the prestressed poise that prepares the body to interact with different spatial layouts.
静止并注视我们前方的一个可见目标是许多协调行为的前提（例如，伸手去拿一个物体）。隐藏在其表面简单性背后的是多层次的纹理。静止站立的任务涉及多个尺度的活动：从确保视网膜上的少数光感受器在极细的尺度上覆盖视野中的目标，到跨越较小尺度的四肢和关节的协同作用，再到脚下地面的机械布局和视野中的光流。在这里，我们使用多尺度概率密度函数 (PDF) 分析来表明姿势波动表现出与在流体流动中发现的级联动力学相似的统计特征。在要求安静站立的参与者中，视觉注视不同距离时的眼动张力调节了姿势级联动力学。在舒适的观看距离进行视觉固定会产生与闭眼时相似的级联动力学的姿势。已知稳定姿势的更大观看距离显示出更减弱的级联动力学。相比之下，需要更大的眼动张力来聚焦目标的最近和最远观看距离会显著增强姿势级联动力学，反映出主动的姿势调整。至关重要的是，这些发现表明，视觉通过重新配置准备与不同空间布局相互作用的预加力平衡来稳定姿势。
