Variability in Human Motor Control

A special issue of Biology (ISSN 2079-7737). This special issue belongs to the section "Biophysics".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 8220

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Université de Bourgogne INSERM-U1093 Cognition, Action, and Sensorimotor Plasticity, Campus Universitaire, BP 27877, 21078 Dijon, France
Interests: motor control and learning; altered gravity; behavioral neuroscience; dexterous manipulation; upper limb movements; bimanual control; internal models; motor imagery; eye movements; perception; cognitive psychology

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1. CeREF, Chaussée de Binche 159, 7000 Mons, Belgium
2. Service de Physique Nucléaire et Subnucléaire, Université de Mons, UMONS Research Institute for Complex Systems, 20 Place du Parc, 7000 Mons, Belgium
Interests: theoretical physics; hadrons; mechanics; fractal analysis; motion analysis; kinematics; modelling complex systems; biomechanics
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Centre National de Rééducation Fonctionnelle et de Réadaptation – Rehazenter, Laboratoire d'Analyse du Mouvement et de la Posture(LAMP), Luxembourg, Luxembourg
Interests: rehabilitation; ergonomy; kinesytherapy; gait analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Evolution has shaped the way in which human beings move. Our ability to learn and perform a wide range of actions has a tremendous impact on daily life. This has opened numerous lines of research and development in the broad areas of medicine, rehabilitation, and sports, but also engineering, robotics, and artificial intelligence. How does the brain control the extremely complex machinery that is our body?

The human body is an overly redundant system. On the one hand, from mathematical and mechanical points of view, it is difficult to control. On the other hand, it is flexible. The central nervous system chooses the unique action among an infinite repertoire through an optimization process in which biomechanical and environmental parameters are considered. As a product of evolution, the brain has learned to integrate this effect of the ubiquitous presence of gravity to move more efficiently. It does not actually see gravity as a perturbation, but as an ally.

Unlike artificial systems, natural actions are characterized by the presence of variability: movements of the finger between two targets, although stereotyped, will never follow exactly the same path. Exactly like gravity, these uncertainties are intrinsically present in the whole decision–action chain, from action planning to motoneurons. This noise has always been considered detrimental, as it reduces performance. What if, like gravity, the brain developed strategies to exploit variability at its advantage? Recent advances inherited from fields outside of the life sciences have highlighted the importance of noise in human motor control. For instance, stochastic resonance and differential learning enhance the performance and generalization of motor skills. Fundamental concepts such as nonlinear time series analysis, fractals, and chaos are very promising tools that could help to decrypt how the brain makes uncertainties speak for themselves.

In this Special Issue titled “Variability in Human Motor Control”, contributions of the latest findings in this area are solicited. The wide scope includes human or animal motor control, biomechanics, rehabilitation, robotics, and movement science. We welcome the contribution of articles of clinical utility or theoretical investigations, including the development of new mathematical or physical tools. One of the aim of the topic is to demonstrate the real added value of multidisciplinary approaches to understand the functional role of noise in the organism. The submission of manuscripts in line with that philosophy are therefore strongly encouraged. We hope that this Special Issue will provide an opportunity to share the state-of-the-art findings in this fascinating area.

Dr. Olivier White
Dr. Fabien Buisseret
Dr. Frédéric Dierick
Prof. Dr. Nandu Goswami
Guest Editors

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Keywords

  • motor control
  • variability
  • fractals
  • mathematical modeling

Published Papers (4 papers)

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12 pages, 8727 KiB  
Article
Adiabatic Invariant of Center-of-Mass Motion during Walking as a Dynamical Stability Constraint on Stride Interval Variability and Predictability
by Fabien Buisseret, Victor Dehouck, Nicolas Boulanger, Guillaume Henry, Florence Piccinin, Olivier White and Frédéric Dierick
Biology 2022, 11(9), 1334; https://0-doi-org.brum.beds.ac.uk/10.3390/biology11091334 - 09 Sep 2022
Cited by 2 | Viewed by 1665
Abstract
Human walking exhibits properties of global stability, and local dynamic variability, predictability, and complexity. Global stability is typically assessed by quantifying the whole-body center-of-mass motion while local dynamic variability, predictability, and complexity are assessed using the stride interval. Recent arguments from general mechanics [...] Read more.
Human walking exhibits properties of global stability, and local dynamic variability, predictability, and complexity. Global stability is typically assessed by quantifying the whole-body center-of-mass motion while local dynamic variability, predictability, and complexity are assessed using the stride interval. Recent arguments from general mechanics suggest that the global stability of gait can be assessed with adiabatic invariants, i.e., quantities that remain approximately constant, even under slow external changes. Twenty-five young healthy participants walked for 10 min at a comfortable pace, with and without a metronome indicating preferred step frequency. Stride interval variability was assessed by computing the coefficient of variation, predictability using the Hurst exponent, and complexity via the fractal dimension and sample entropy. Global stability of gait was assessed using the adiabatic invariant computed from averaged kinetic energy value related to whole-body center-of-mass vertical displacement. We show that the metronome alters the stride interval variability and predictability, from autocorrelated dynamics to almost random dynamics. However, despite these large local variability and predictability changes, the adiabatic invariant is preserved in both conditions, showing the global stability of gait. Thus, the adiabatic invariant theory reveals dynamical global stability constraints that are “hidden” behind apparent local walking variability and predictability. Full article
(This article belongs to the Special Issue Variability in Human Motor Control)
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11 pages, 831 KiB  
Article
Running-Induced Fatigue Changes the Structure of Motor Variability in Novice Runners
by Felix Möhler, Cagla Fadillioglu, Lucia Scheffler, Hermann Müller and Thorsten Stein
Biology 2022, 11(6), 942; https://0-doi-org.brum.beds.ac.uk/10.3390/biology11060942 - 20 Jun 2022
Cited by 2 | Viewed by 2539
Abstract
Understanding the effects of fatigue is a central issue in the context of endurance sports. Given the popularity of running, there are numerous novices among runners. Therefore, understanding the effects of fatigue in novice runners is an important issue. Various studies have drawn [...] Read more.
Understanding the effects of fatigue is a central issue in the context of endurance sports. Given the popularity of running, there are numerous novices among runners. Therefore, understanding the effects of fatigue in novice runners is an important issue. Various studies have drawn conclusions about the control of certain variables by analyzing motor variability. One variable that plays a crucial role during running is the center of mass (CoM), as it reflects the movement of the whole body in a simplified way. Therefore, the aim of this study was to analyze the effects of fatigue on the motor variability structure that stabilizes the CoM trajectory in novice runners. To do so, the uncontrolled manifold approach was applied to a 3D whole-body model using the CoM as the result variable. It was found that motor variability increased with fatigue (UCM). However, the UCMRatio did not change. This indicates that the control of the CoM decreased, whereas the stability was not affected. The decreases in control were correlated with the degree of exhaustion, as indicated by the Borg scale (during breaking and flight phase). It can be summarized that running-induced fatigue increases the step-to-step variability in novice runners and affects the control of their CoM. Full article
(This article belongs to the Special Issue Variability in Human Motor Control)
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17 pages, 1583 KiB  
Article
Higher Responsiveness of Pattern Generation Circuitry to Sensory Stimulation in Healthy Humans Is Associated with a Larger Hoffmann Reflex
by Irina A. Solopova, Victor A. Selionov, Egor O. Blinov, Irina Y. Dolinskaya, Dmitry S. Zhvansky, Francesco Lacquaniti and Yury Ivanenko
Biology 2022, 11(5), 707; https://0-doi-org.brum.beds.ac.uk/10.3390/biology11050707 - 05 May 2022
Cited by 3 | Viewed by 1580
Abstract
The state and excitability of pattern generators are attracting the increasing interest of neurophysiologists and clinicians for understanding the mechanisms of the rhythmogenesis and neuromodulation of the human spinal cord. It has been previously shown that tonic sensory stimulation can elicit non-voluntary stepping-like [...] Read more.
The state and excitability of pattern generators are attracting the increasing interest of neurophysiologists and clinicians for understanding the mechanisms of the rhythmogenesis and neuromodulation of the human spinal cord. It has been previously shown that tonic sensory stimulation can elicit non-voluntary stepping-like movements in non-injured subjects when their limbs were placed in a gravity-neutral unloading apparatus. However, large individual differences in responsiveness to such stimuli were observed, so that the effects of sensory neuromodulation manifest only in some of the subjects. Given that spinal reflexes are an integral part of the neuronal circuitry, here we investigated the extent to which spinal pattern generation excitability in response to the vibrostimulation of muscle proprioceptors can be related to the H-reflex magnitude, in both the lower and upper limbs. For the H-reflex measurements, three conditions were used: stationary limbs, voluntary limb movement and passive limb movement. The results showed that the H-reflex was considerably higher in the group of participants who demonstrated non-voluntary rhythmic responses than it was in the participants who did not demonstrate them. Our findings are consistent with the idea that spinal reflex measurements play important roles in assessing the rhythmogenesis of the spinal cord. Full article
(This article belongs to the Special Issue Variability in Human Motor Control)
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13 pages, 2439 KiB  
Brief Report
Error Size Shape Relationships between Motor Variability and Implicit Motor Adaptation
by Naoyoshi Matsuda and Masaki O. Abe
Biology 2023, 12(3), 404; https://0-doi-org.brum.beds.ac.uk/10.3390/biology12030404 - 03 Mar 2023
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Abstract
Previous studies have demonstrated the effects of motor variability on motor adaptation. However, their findings have been inconsistent, suggesting that various factors affect the relationship between motor variability and adaptation. This study focused on the size of errors driving motor adaptation as one [...] Read more.
Previous studies have demonstrated the effects of motor variability on motor adaptation. However, their findings have been inconsistent, suggesting that various factors affect the relationship between motor variability and adaptation. This study focused on the size of errors driving motor adaptation as one of the factors and examined the relationship between different error sizes. Thirty-one healthy young adults participated in a visuomotor task in which they made fast-reaching movements toward a target. Motor variability was measured in the baseline phase when a veridical feedback cursor was presented. In the adaptation phase, the feedback cursor was sometimes not reflected in the hand position and deviated from the target by 0°, 3°, 6°, or 12° counterclockwise or clockwise (i.e., error-clamp feedback). Movements during trials following trials with error-clamp feedback were measured to quantify implicit adaptation. Implicit adaptation was driven by errors presented through error-clamp feedback. Moreover, motor variability significantly correlated with implicit adaptation driven by a 12° error. The results suggested that motor variability accelerates implicit adaptation when a larger error occurs. As such a trend was not observed when smaller errors occurred, the relationship between motor variability and motor adaptation might have been affected by the error size driving implicit adaptation. Full article
(This article belongs to the Special Issue Variability in Human Motor Control)
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