Scaling oscillatory platform frequency reveals recurrence of intermittent postural attractor states

Abstract

The study of postural control has been dominated by experiments on the maintenance of quiet upright standing balance on flat stationary support surfaces that reveal only limited modes of potential configurations of balance stability/instability. Here we examine the self-organization properties of postural coordination as revealed in a dynamic balance task with a moving platform. We scaled a control parameter (platform frequency) to investigate the evolving nature of the coupled oscillator dynamics between center of mass (CoM) and platform. Recurrent map measures were used to reveal whether episodic postural control strategies exist that can be scaled by systematically changing the magnitude of platform motion. The findings showed that at higher platform frequencies (1.2 Hz), the CoM-Platform coupling was less deterministic than lower platform frequencies and evolved to intermittent postural control strategies that oscillated between periodic-chaotic transitions to maintain upright postural balance. Collectively, the recurrence map measures indicated that quasi-static postural attractor states were progressively emerging to the changing task constraints of platform frequency in the maintenance of postural stability. It appears that several dynamic modes of intermittent coupling in postural control can interchangeably co-exist and are expressed as a function of the control parameter of platform frequency.

Adaptation of balancing behaviour during continuous perturbations of stance. Supra-postural visual tasks and platform translation frequency modulate adaptation rate

“…Adaptation to repeated perturbations of balance has been investigated [46,[52][53][54][55][56][57][58]. Vision of the environment is able to exert a substantial effect on head stabilisation when balancing on a continuously translating platform [8,9].…”

“…The adaptation time course of the CC is not different across all visual conditions within each frequency, suggesting that the performance of the supra-postural task does not interfere with the coordination between pelvis and head. The scarcely coordinated control of pelvis and head at HF [56] would require a costly and long process (a longer time constant than at LF) to maintain the equilibrium as if the performance of the visual tasks would be left to second plan compared to the control of balance. The difficulty in the balancing task and the need for swiftly minimizing energy use for balancing [79] seem to overwhelm the effect of the supra-postural task at HF.…”

Vision Does Not Necessarily Stabilize the Head in Space During Continuous Postural Perturbations

“…If the hypothesis would be confirmed, head stabilization in space would not be necessarily equivalent to “better” balance. The flexibility of coordination modes (34) and its complying with non-postural tasks would speak for the capacity of the nervous system to adaptively modulate the weight attributed to balance-relevant sensory inputs. On the translational side, since continuous movement of the supporting platform, with eyes-open or eyes-closed, has been exploited as a rehabilitation procedure for various populations with balance disorders (24, 27, 35, 36), adding to the training protocol visual tasks that challenge the visual integration process may offer an additional tool for understanding and treating these disorders.…”

Age-Related Changes in Standing Balance in Preschoolers Using Traditional and Nonlinear Methods

“…Center of pressure sway’s intermittency increased for the 5-year-old children compared with the 3- and 4-year-old children, as shown by higher %LAM_ap. The intermittent behavior of COP motion reflects an intermittent control mechanism of standing balance ( Nomura et al, 2013 ; Dutt-Mazumder et al, 2018 ; Stins and Roerdink, 2018 ), which is manifested as the COP motion exhibiting changes in COP dynamics from fluctuating to relatively stationary ( van den Hoorn et al, 2018 ). In fact, a decrease in the %LAM was observed with aging for the elderly compared with the young adults, and a reduction in the %LAM was also found for older fallers compared with older non-fallers ( van den Hoorn et al, 2018 ).…”