Postural instability via a loss of intermittent control in elderly and patients with Parkinson’s disease: A model-based and data-driven approach

Abstract

Postural instability is one of the major symptoms of Parkinson’s disease. Here, we assimilated a model of intermittent delay feedback control during quiet standing into postural sway data from healthy young and elderly individuals as well as patients with Parkinson’s disease to elucidate the possible mechanisms of instability. Specifically, we estimated the joint probability distribution of a set of parameters in the model using the Bayesian parameter inference such that the model with the inferred parameters can best-fit sway data for each individual. It was expected that the parameter values for three populations would distribute differently in the parameter space depending on their balance capability. Because the intermittent control model is parameterized by a parameter associated with the degree of intermittency in the control, it can represent not only the intermittent model but also the traditional continuous control model with no intermittency. We showed that the inferred parameter values for the three groups of individuals are classified into two major groups in the parameter space: one represents the intermittent control mostly for healthy people and patients with mild postural symptoms and the other the continuous control mostly for some elderly and patients with severe postural symptoms. The results of this study may be interpreted by postulating that increased postural instability in most Parkinson’s patients and some elderly persons might be characterized as a dynamical disease.

Long-Lasting Event-Related Beta Synchronizations of Electroencephalographic Activity in Response to Support-Surface Perturbations During Upright Stance: A Pilot Study Associating Beta Rebound and Active Monitoring in the Intermittent Postural Control

“…In this section, we overview fundamental neuromechanics of upright posture during quiet stance and those in response to a support-surface perturbation, based on the intermittent control model (Bottaro et al, 2008;Asai et al, 2009;Nomura et al, 2020;Suzuki et al, 2020) to clarify the perspectives of this study. To this end, we consider an inverted pendulum model of human upright stance, stabilized by an intermittent feedback controller.…”

“…Supraspinal contributions to postural stabilization during human upright stance have been demonstrated by postural instability in patients with neurological disorders such as Parkinson's disease (PD), multiple sclerosis, and stroke (e.g., Horak et al, 1992;Frzovic et al, 2000;Geurts et al, 2005;Visser et al, 2008;Perera et al, 2018;Suzuki et al, 2020). Because impairment of postural stability due to neurological diseases is one of the major qualityof-life factors (Sterling et al, 2001) and it has also been linked to individual fall risks (Zhou et al, 2017), understanding the supraspinal information processing for stabilizing upright stance is of crucial importance for our aging societies.…”

“…However, if we observe beta ERD and ERS with qualitative differences in temporal characterizations from those during upper extremity tasks, they could lead to shedding new light on mechanistic causes of the beta rebound. Indeed, the final phase of the postural recovery has a particular meaning for the intermittent control hypothesis that has received attention in recent years (Bottaro et al, 2008;Asai et al, 2009;Xiang et al, 2018;Suzuki et al, 2020), as elaborated in the next section. That is, the final phase of postural recovery takes place with a small postural tilt, during which, according to the intermittent control hypothesis, the active feedback control is switched off, and the postural state point approaches slowly the upright posture along a stable manifold of the unstable saddle-type upright equilibrium in the state space of postural control system.…”

Idiosyncratic Characteristics of Postural Sway in Normal and Perturbed Standing

“…Furthermore, PF50 analysis shows that there is no significant rise in frequency during tilting, so we suggest that it is the mean amplitude of the sway that increases. Sway amplitude, which expresses the amount that an individual wobbles, is often intuitively associated with instability although this is not necessarily true (Suzuki et al, 2020).…”

“…These studies have focused on postural sway size as a measure of group behavior. Unsurprisingly, postural sway size is often thought of as an indicator of instability although this is not necessarily so (for example Suzuki et al, 2020). Less attention has been directed at sway size as an individual characteristic.…”