Visual effort moderates postural cascade dynamics

Abstract

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 distribution function (PDF) analysis to show that postural fluctuations exhibit similar statistical signatures of cascade dynamics as found in fluid flow. Critically, the oculomotor strain of visually fixating different distances moderates 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 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.

Point estimates, Simpson’s paradox, and nonergodicity in biological sciences

“…However, this starting position is not merely the preamble to action but is already a rich wellspring of action itself, exhibiting a continuous stream of intermittent fluctuations. So long as they do not pitch the bodily center of pressure (CoP) beyond the base of support, these fluctuations are crucial to maintaining a quiet stance 58,59 . Therefore, it is surprising that the prevailing statistical methods make an indiscriminate assumption of ergodicity, feeding the bias to study systems while they are in equilibrium because only then can the behavior be measured to obtain a point estimate.…”

Multifractality in postural sway supports quiet eye training in aiming tasks: A study of golf putting

“…Thus, it is believed that instructing athletes by directing their perceptual linkages outward to the visual field supports higher task performance as well as leads to more expert-like movement and physiology. QE research opens a fascinating vantage point to situate ongoing research on linkages anchoring organisms to their visual contexts and the synergies transforming visual information into action (e.g., [14][15][16]). Research on QE has mostly examined the visual-cognitive bases for the relatively more extraverted gaze into the task context [8,17,18], and the relationship of QE to the body, the brain, and the nervous system has received relatively less attention [19][20][21].…”