Fractal properties in sensorimotor variability unveil internal adaptations of the organism before symptomatic functional decline

Kjerstin Torre,Éric Viel,Stéphane Perrey,Grégoire Vergotte,Arnaud Dupeyron

doi:10.1038/s41598-019-52091-y

Kjerstin Torre, Éric Viel + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-52091-y

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Abstract

If health can be defined as adaptability, then measures of adaptability are crucial. Convergent findings across clinical areas established the notion that fractal properties in bio-behavioural variability characterize the healthy condition of the organism, and its adaptive capacities in general. However, ambiguities remain as to the significance of fractal properties: the literature mainly discriminated between healthy vs. pathological states, thereby loosing perspective on the progression in between, and overlooking the distinction between adaptability and effective adaptations of the organism. Here, we design an experimental tapping paradigm involving gradual feedback deprivation in groups of healthy subjects and one deafferented man as a pathological-limit case. We show that distinct types of fractal properties in sensorimotor behaviour characterize, on the one hand impaired functional ability, and on the other hand internal adaptations for maintaining performance despite the imposed constraints. Findings may prove promising for early detection of internal adaptations preceding symptomatic functional decline.

Highlights

If health can be defined as adaptability, measures of adaptability are crucial
If time series complexity is a hallmark of organism’s adaptability as a cross-cutting factor, this relationship is necessarily transposable to various circumstances outside of pathology or aging: one could assume that experimentally-induced constraints mimicking pathology- or age-associated impairments would alter the complexity of functional variables in a similar way
On account of these issues, one cannot ascertain whether an alteration of complexity in the organism’s variables reflects mechanisms related to pathology, or the loss of adaptability associated with impaired conditions, or effective adaptations of the organism as a whole to maintain its functional level as far as possible when facing constraints

Summary

Introduction

Convergent findings across clinical areas established the notion that fractal properties in bio-behavioural variability characterize the healthy condition of the organism, and its adaptive capacities in general. Effective adaptations occurring at any level of the system may affect further adaptability[28,29] On account of these issues, one cannot ascertain whether an alteration of complexity in the organism’s variables reflects mechanisms related to pathology, or the loss of adaptability associated with impaired conditions, or effective adaptations of the organism as a whole to maintain its functional level as far as possible when facing constraints. We analysed the mono- and multifractal properties of the series of inter-tap intervals produced We expected that this experimental paradigm would contribute to unravel how fractal properties in bio-behavioural variability characterize adaptability, adaptation, and healthy or pathological

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