Center of Pressure Feedback Modulates the Entrainment of Voluntary Sway to the Motion of a Visual Target

Abstract

Visually guided weight shifting is widely employed in balance rehabilitation, but the underlying visuo-motor integration process leading to balance improvement is still unclear. In this study, we investigated the role of center of pressure (CoP) feedback on the entrainment of active voluntary sway to a moving visual target and on sway’s dynamic stability as a function of target predictability. Fifteen young and healthy adult volunteers (height 175 ± 7 cm, body mass 69 ± 12 kg, age 32 ± 5 years) tracked a vertically moving visual target by shifting their body weight antero-posteriorly under two target motion and feedback conditions, namely, predictable and less predictable target motion, with or without visual CoP feedback. Results revealed lower coherence, less gain, and longer phase lag when tracking the less predictable compared to the predictable target motion. Feedback did not affect CoP-target coherence, but feedback removal resulted in greater target overshooting and a shorter phase lag when tracking the less predictable target. These adaptations did not affect the dynamic stability of voluntary sway. It was concluded that CoP feedback improves spatial perception at the cost of time delays, particularly when tracking a less predictable moving target.

Standing on unstable surface challenges postural control of tracking tasks and modulates neuromuscular adjustments specific to task complexity

“…1 ). As in previous studies 14 , 25 the target had the shape of a dot which moved in the middle of the screen in a vertical direction. Upwards motion of the dot corresponded to anterior direction of the CoP, while downwards motion to posterior CoP direction.…”

“…Unstable conditions during visually guided postural tasks may challenge the neuromotor system to maintain stability and may initiate specific modifications in motor control in order to counteract or compensate for the external induced perturbations. The complexity of the target motion is an additional condition influencing the visuo-motor coupling performance 24 , 25 . A target moving in an unpredictable, more complex way (chaotic) than a predictable, less complex one (sinusoidal), deteriorates postural sway and target motion coherence 24 , 25 evidencing the effects of target complexity on the visuo-motor performance.…”

“…The complexity of the target motion is an additional condition influencing the visuo-motor coupling performance 24 , 25 . A target moving in an unpredictable, more complex way (chaotic) than a predictable, less complex one (sinusoidal), deteriorates postural sway and target motion coherence 24 , 25 evidencing the effects of target complexity on the visuo-motor performance. Oullier et al 26 using the moving room paradigm found a decrease in the room-head coupling with increasing room frequency depicting a demand-dependent deterioration of visual coupling performance.…”

Conditional adaptive Bayesian spectral analysis of replicated multivariate time series

“…However, such an extension will lead to a dramatic increase in computational complexity and will likely require some form of simultaneous dimension reduction or efficient approximation of the true nature of the association. Finally, future work will aim to expand the preliminary study of postural instability and fear of falling in PD patients by (1) expanding the number of PD patients in order to validate the initial findings presented in Section 5 of this article, and (2) incorporating dynamic balance tasks, such as visually guided weight shifting tasks, 44 to evaluate dynamic postural control mechanisms in PD patients. The current analysis only considers postural stability while standing still, which only allows for assessment of static postural control mechanisms.…”

Special Issue: Movement Biomechanics and Motor Control

“…This special issue provides a demonstration of this. The papers collected deal with anticipatory postural adjustments [2] and anticipatory locomotor adjustments [3], strategies to tackle obstacles [2][3][4], the effects of weight unloading on gait [5], posture control in special populations: ataxic children [6] and obese subjects [7], surface perturbation during posture [8], effects of sensory information and feedback on postural control [9,10], elderly behavior during a motor-motor double task [11], upper limb control [12,13], different aspects related to running: ankle joint dynamic stiffness [14] and fatigue [15]. There is also a flash on an ecologic condition where a pedestrian has to program its strategy to cross a road in between two moving vehicles [16], and a study on visual-manual control in monkeys [17].…”