Performance-Stabilizing Synergies in a Complex Motor Skill: Analysis Based on the Uncontrolled Manifold Hypothesis

Motor Control ◽  
2020 ◽  
Vol 24 (2) ◽  
pp. 238-252
Author(s):  
Fariba Hasanbarani ◽  
Mark L. Latash
Keyword(s):  
Hierarchical Control ◽  
Uncontrolled Manifold ◽  
Time Varying ◽  
Uncontrolled Manifold Hypothesis ◽  
Small Ball ◽  
Complex Motor ◽  
Eyes Open ◽  
Skill Analysis ◽  
Joint Velocity ◽  
Different Levels

The authors studied indices of stability (ΔV) of two time-varying variables, hand coordinate and velocity, during accurate throw of a small ball into the basket. Ten participants performed the throwing task with eyes-open (vision) and -closed (no vision) conditions. In the latter condition, participants closed their eyes prior to initiating the throw. The intertrial variance in the joint configuration space (and joint velocity space) was analyzed based on the uncontrolled manifold hypothesis. The results confirmed the presence of both coordinate- and velocity-stabilizing synergies (ΔV > 0). Intertrial variance was larger in the no-vision condition compared with the vision condition. Over the movement duration, ΔV did not change for the coordinate-related analysis but dropped consistently for the velocity-related analysis. The authors interpret the findings within the idea of hierarchical control and trade-off between synergy indices at different levels of the hierarchy.

scholarly journals Number of Trials Necessary to Apply Analysis within the Framework of the Uncontrolled Manifold Hypothesis at Different Levels of Hierarchical Synergy Control

2021 ◽  
Vol 76 (1) ◽  
pp. 131-143
Author(s):  
Michał Pawłowski ◽  
Mariusz P. Furmanek ◽  
Grzegorz Sobota ◽  
Wojciech Marszałek ◽  
Kajetan J. Słomka ◽  
...  
Keyword(s):  
Intraclass Correlation ◽  
Hierarchical Control ◽  
Large Body ◽  
Elbow Flexion ◽  
Uncontrolled Manifold ◽  
Uncontrolled Manifold Hypothesis ◽  
Motor Synergies ◽  
Minimum Number ◽  
Motor Actions ◽  
Different Levels

Abstract The uncontrolled manifold hypothesis is a method used to quantify motor synergies, defined as a specific central nervous system organization that maintains the task-specific stability of motor actions. The UCM allows for inter-trial variance analysis between consecutive trials. However, despite the large body of literature within this framework, there is no report on the number of movement repetitions required for reliable results. Based on the hypothetical hierarchical control of motor synergies, this study aims to determine the minimum number of trials necessary to achieve a good to excellent level of reliability. Thirteen young, healthy participants performed fifteen bilateral isometric contractions of elbow flexion when visual feedback was provided. The force and electromyography data were recorded to investigate synergies at different levels of hierarchical control. The intraclass correlation coefficient was used to determine the reliability of the variance indices. Based on the obtained results, at least twelve trials are required to analyze the inter-trial variance in both force and muscle synergies within the UCM framework.

scholarly journals The Hand: Shall We Ever Understand How It Works?

Motor Control ◽  
2015 ◽  
Vol 19 (2) ◽  
pp. 108-126 ◽  
Author(s):  
Mark L. Latash
Keyword(s):  
Motor Control ◽  
Equilibrium Point ◽  
Neurological Disorder ◽  
Neural Control ◽  
Hierarchical Control ◽  
Uncontrolled Manifold ◽  
Human Hand ◽  
Uncontrolled Manifold Hypothesis ◽  
Target Article ◽  
Point Control

The target article presents a review of the neural control of the human hand. The review emphasizes the physical approach to motor control. It focuses on such concepts as equilibrium-point control, control with referent body configurations, uncontrolled manifold hypothesis, principle of abundance, hierarchical control, multidigit synergies, and anticipatory synergy adjustments. Changes in aspects of the hand neural control with age and neurological disorder are discussed. The target article is followed by six commentaries written by Alexander Aruin, Kelly Cole, Monica Perez, Robert Sainburg, Marco Sanello, and Wei Zhang.

New Models for Motor Control

1989 ◽  
Vol 1 (2) ◽  
pp. 173-183 ◽  
Author(s):  
Jennifer S. Altman ◽  
Jenny Kien
Keyword(s):  
Distributed Control ◽  
Hierarchical Control ◽  
Sensory Information ◽  
Striking Similarity ◽  
Maximum Efficiency ◽  
Behavioral Choice ◽  
Modular Control ◽  
Superficial Resemblance ◽  
Different Levels ◽  
Command Center

What do a prototype robot (Brooks 1989) and a model for the control of behavioral choice in insects (Altman and Kien 1987a) have in common? And what do they share with a scratching cat (Shadmehr 1989)? The answer is distributed control systems that do not depend on a central command center for the execution of behavioral outputs. The first two in particular are examples of a growing trend to replace the long-held concept of linear hierarchical control of motor output with one of decentralized, distributed control, with inputs at many levels and the output a consensus of the activity in several centers. Brooks (1989) describes a six-legged machine that, in its most advanced form, can walk over rough terrain and prowl around following a source of warmth, such as a person. The six legs, chosen as a compromise between stability and ease of coordination, give the robot a superficial resemblance to an insect — but the similarity goes deeper. The modular control system, designed strictly on engineering principles for maximum efficiency and economy, bears a striking similarity to the model we have proposed elsewhere (Altman and Kien 1987a) to describe the organization of the motor system in insects such as the locust. In both systems, the same set of components can generate different behaviors, depending on the context, and similar principles govern the generation of different levels of behavior, from movements of a single leg to coordinated responses of the whole beast. Neither requires a single center for integrating all sensory information and conflicts tend to be resolved by consensus at the motor level.

scholarly journals Synergies in coordination: a comprehensive overview of neural, computational, and behavioral approaches

2018 ◽  
Vol 120 (6) ◽  
pp. 2761-2774 ◽  
Author(s):  
Michaela Bruton ◽  
Nicholas O’Dwyer
Keyword(s):  
Motor Control ◽  
Hierarchical Control ◽  
Research Approach ◽  
Comprehensive Overview ◽  
Control Scheme ◽  
The One ◽  
Explanatory Concept ◽  
Different Levels ◽  
And Task

At face value, the term “synergy” provides a unifying concept within a fractured field that encompasses complementary neural, computational, and behavioral approaches. However, the term is not used synonymously by different researchers but has substantially different meanings depending on the research approach. With so many operational definitions for the one term, it becomes difficult to use as either a descriptive or explanatory concept, yet it remains pervasive and apparently indispensable. Here we provide a summary of different approaches that invoke synergies in a descriptive or explanatory context, summarizing progress, not within the one approach, but across the theoretical landscape. Bernstein’s framework of flexible hierarchical control may provide a unifying framework here, since it can incorporate divergent ideas about synergies. In the current motor control literature, synergy may refer to conceptually different processes that could potentially operate in parallel, across different levels within the same hierarchical control scheme. There is evidence for the concurrent existence of synergies with different features, both “hard-wired” and “soft-wired,” and task independent and task dependent. By providing a comprehensive overview of the multifaceted ideas about synergies, our goal is to move away from the compartmentalization and narrow the focus on one level and promote a broader perspective on the control and coordination of movement.

scholarly journals Equifinality and its violations in a redundant system: multifinger accurate force production

2013 ◽  
Vol 110 (8) ◽  
pp. 1965-1973 ◽  
Author(s):  
Luke Wilhelm ◽  
Vladimir M. Zatsiorsky ◽  
Mark L. Latash
Keyword(s):  
Force Production ◽  
Uncontrolled Manifold ◽  
Total Force ◽  
Redundant System ◽  
Uncontrolled Manifold Hypothesis ◽  
Final State ◽  
Performance Variables ◽  
Force Mode ◽  
Finger Forces ◽  
The Individual

We explored a hypothesis that transient perturbations applied to a redundant system result in equifinality in the space of task-related performance variables but not in the space of elemental variables. The subjects pressed with four fingers and produced an accurate constant total force level. The “inverse piano” device was used to lift and lower one of the fingers smoothly. The subjects were instructed “not to intervene voluntarily” with possible force changes. Analysis was performed in spaces of finger forces and finger modes (hypothetical neural commands to fingers) as elemental variables. Lifting a finger led to an increase in its force and a decrease in the forces of the other three fingers; the total force increased. Lowering the finger back led to a drop in the force of the perturbed finger. At the final state, the sum of the variances of finger forces/modes computed across repetitive trials was significantly higher than the variance of the total force/mode. Most variance of the individual finger force/mode changes between the preperturbation and postperturbation states was compatible with constant total force. We conclude that a transient perturbation applied to a redundant system leads to relatively small variance in the task-related performance variable (equifinality), whereas in the space of elemental variables much more variance occurs that does not lead to total force changes. We interpret the results within a general theoretical scheme that incorporates the ideas of hierarchically organized control, control with referent configurations, synergic control, and the uncontrolled manifold hypothesis.

scholarly journals Stability of hand force production. II. Ascending and descending synergies

2018 ◽  
Vol 120 (3) ◽  
pp. 1045-1060 ◽  
Author(s):  
Sasha Reschechtko ◽  
Mark L. Latash
Keyword(s):  
Visual Feedback ◽  
Neural Control ◽  
Uncontrolled Manifold ◽  
Total Force ◽  
Level Control ◽  
Control Variables ◽  
Specific Level ◽  
Referent Coordinate ◽  
Apparent Stiffness ◽  
Different Levels

We combined the theory of neural control of movement with referent coordinates and the uncontrolled manifold hypothesis to investigate multifinger coordination. We tested hypotheses related to stabilization of performance by covarying control variables, translated into apparent stiffness and referent coordinate, at different levels of an assumed hierarchy of control. Subjects produced an accurate combination of total force and total moment of force with the four fingers under visual feedback on both variables and after feedback was partly or completely removed. The “inverse piano” device was used to estimate control variables. We observed strong synergies in the space of hypothetical control variables that stabilized total force and moment of force, as well as weaker synergies stabilizing individual finger forces; whereas the former were attenuated by alteration of visual feedback, the latter were much less affected. In addition, we investigated the organization of “ascending synergies” stabilizing task-level control variables by covaried adjustments of finger-level control variables. We observed intertrial covariation of individual fingers’ referent coordinates that stabilized hand-level referent coordinate, but we observed no such covariation for apparent stiffness. The observations suggest the existence of both descending and ascending synergies in a hierarchical control system. They confirm a trade-off between synergies at different levels of control and corroborate the hypothesis on specialization of different fingers for the control of force and moment. The results provide strong evidence for the importance of central back-coupling loops in ensuring stability of action.NEW & NOTEWORTHY We expand analysis of action in the space of hypothetical control variables to hierarchically organized multieffector systems. We also introduce the novel concept of ascending synergies, which reflect covariation of control variables to individual effectors (fingers) that stabilize task-specific control variables at a hierarchically higher, task-specific level (hand).

scholarly journals Association of Time–Varying Intensity of Ventilation With Mortality in Patients With COVID−19 ARDS: Secondary Analysis of the PRoVENT–COVID Study

2021 ◽  
Vol 8 ◽  
Author(s):  
Michiel T. U. Schuijt ◽  
David M. P. van Meenen ◽  
Ignacio Martin–Loeches ◽  
Guido Mazzinari ◽  
Marcus J. Schultz ◽  
...  
Keyword(s):  
Distress Syndrome ◽  
Secondary Analysis ◽  
Fixed Time ◽  
Sensitivity Analyses ◽  
Cumulative Exposure ◽  
Time Varying ◽  
Joint Models ◽  
Clinical Trial Registration ◽  
Increased Risk ◽  
Different Levels

Background: High intensity of ventilation has an association with mortality in patients with acute respiratory failure. It is uncertain whether similar associations exist in patients with acute respiratory distress syndrome (ARDS) patients due to coronavirus disease 2019 (COVID−19). We investigated the association of exposure to different levels of driving pressure (ΔP) and mechanical power (MP) with mortality in these patients.Methods: PRoVENT–COVID is a national, retrospective observational study, performed at 22 ICUs in the Netherlands, including COVID−19 patients under invasive ventilation for ARDS. Dynamic ΔP and MP were calculated at fixed time points during the first 4 calendar days of ventilation. The primary endpoint was 28–day mortality. To assess the effects of time–varying exposure, Bayesian joint models adjusted for confounders were used.Results: Of 1,122 patients included in the PRoVENT–COVID study, 734 were eligible for this analysis. In the first 28 days, 29.2% of patients died. A significant increase in the hazard of death was found to be associated with each increment in ΔP (HR 1.04, 95% CrI 1.01–1.07) and in MP (HR 1.12, 95% CrI 1.01–1.36). In sensitivity analyses, cumulative exposure to higher levels of ΔP or MP resulted in increased risks for 28–day mortality.Conclusion: Cumulative exposure to higher intensities of ventilation in COVID−19 patients with ARDS have an association with increased risk of 28–day mortality. Limiting exposure to high ΔP or MP has the potential to improve survival in these patients.Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT04346342.

The origin of the oppositional patterns of cultural diversity in different levels

2020 ◽  
Vol 31 (08) ◽  
pp. 2050105
Author(s):  
You-Zhao Gou ◽  
Jun-Ying Cui ◽  
Xiao-Pu Han
Keyword(s):  
Cultural Diversity ◽  
Numerical Simulations ◽  
Mobile Agents ◽  
Cultural Difference ◽  
Social Systems ◽  
Communication Cost ◽  
Time Varying ◽  
Cultural Characteristics ◽  
Modeling Framework ◽  
Different Levels

The evolution of cultural diversity in some social systems can be observed as the oppositional patterns in different levels, namely, the directions of the trends of diversity in different levels are opposite. In this paper, we propose a payoff-driven metapopulation modeling framework to investigate the origin of the oppositional patterns in the trends of cultural diversity. This model considers the mobile agents in multiple communities, and the cultural characteristics of an agent are represented by a vector. The diffusion of cultural characteristics is driven by two opposite effects: the communication cost positively depending on cultural difference between agents, and the cultural attractiveness single-peak-functional correlating on cultural difference. In the numerical simulations of the model, the polarization is observed in the case with the homophily principle, and two types of the oppositional patterns can emerge in the case with time-varying mobility of agents. These findings efficiently explain the emergence of the oppositional patterns and help to understand the evolution of diversity under the dynamics of both synchronization and variation.

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