Analysis of motor synergies within the uncontrolled manifold hypothesis

2014 ◽  
Vol 39 ◽  
pp. S78
Keyword(s):  
Uncontrolled Manifold ◽  
Uncontrolled Manifold Hypothesis ◽  
Motor Synergies

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.

Abundant Degrees of Freedom Are Not a Problem

2018 ◽  
Vol 7 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Mark L. Latash
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Methods ◽  
Uncontrolled Manifold ◽  
Motor Tasks ◽  
Uncontrolled Manifold Hypothesis ◽  
Motor Synergies ◽  
External Forces ◽  
Applied Fields ◽  
The Brain ◽  
Additional Constraints

The problem of motor redundancy has been one of the fundamental, albeit elusive, problems in motor control. Traditionally, it has been viewed as a computational problem for the brain, solved with either optimization methods or by introducing additional constraints to motor tasks. This review suggests that the problem was wrongly formulated, and that the abundant degrees of freedom are not to be eliminated but used to ensure dynamic stability of motor performance, which is vital given the unpredictable intrinsic states and external forces. The idea of synergies as mechanisms ensuring action stability is introduced based on the uncontrolled manifold hypothesis and the theory of control with spatial referent coordinates. The importance of controlled stability is illustrated with the phenomena of anticipatory synergy adjustments. This approach is productive for both basic and applied fields as illustrated, in particular, by changes in motor synergies with neurological disorder and exercise.

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 Postural Synergies and Their Development

2005 ◽  
Vol 12 (2-3) ◽  
pp. 119-130 ◽  
Author(s):  
Mark L. Latash ◽  
Vijaya Krishnamoorthy ◽  
John P. Scholz ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Uncontrolled Manifold ◽  
Motor Tasks ◽  
Performance Variables ◽  
Motor Synergies ◽  
Motor Abundance ◽  
Motor Practice ◽  
Recent Developments ◽  
The Central Nervous System ◽  
Postural Perturbations ◽  
Postural Synergies

The recent developments of a particular approach to analyzing motor synergies based on the principle of motor abundance has allowed a quantitative assessment of multieffector coordination in motor tasks involving anticipatory adjustments to self-triggered postural perturbations and in voluntary posturalsway. This approach, the uncontrolled manifold (UCM) hypothesis, is based on an assumption that the central nervous system organizes covariation of elemental variables to stabilize important performance variables in a task-specific manner. In particular, this approach has been used to demonstrate and to assess the emergence of synergies and their modification with motor practice in typical persons and persons with Down syndrome. The framework of the UCM hypothesis allows the formulation of testable hypotheses with respect to developing postural synergies in typically and atypically developing persons.

scholarly journals The human motor system alters its reaching movement plan for task-irrelevant, positional forces

2015 ◽  
Vol 113 (7) ◽  
pp. 2137-2149 ◽  
Author(s):  
Joshua G. A. Cashaback ◽  
Heather R. McGregor ◽  
Paul L. Gribble
Keyword(s):  
Uncontrolled Manifold ◽  
Movement Trajectory ◽  
Uncontrolled Manifold Hypothesis ◽  
Natural Behavior ◽  
Reaching Movement ◽  
Task Success ◽  
Human Motor ◽  
Hypothesis State ◽  
Task Irrelevant ◽  
Active Exploration

The minimum intervention principle and the uncontrolled manifold hypothesis state that our nervous system only responds to force perturbations and sensorimotor noise if they affect task success. This idea has been tested in muscle and joint coordinate frames and more recently using workspace redundancy (e.g., reaching to large targets). However, reaching studies typically involve spatial and or temporal constraints. Constrained reaches represent a small proportion of movements we perform daily and may limit the emergence of natural behavior. Using more relaxed constraints, we conducted two reaching experiments to test the hypothesis that humans respond to task-relevant forces and ignore task-irrelevant forces. We found that participants responded to both task-relevant and -irrelevant forces. Interestingly, participants experiencing a task-irrelevant force, which simply pushed them into a different area of a large target and had no bearing on task success, changed their movement trajectory prior to being perturbed. These movement trajectory changes did not counteract the task-irrelevant perturbations, as shown in previous research, but rather were made into new areas of the workspace. A possible explanation for this behavior change is that participants were engaging in active exploration. Our data have implications for current models and theories on the control of biological motion.

scholarly journals Visual feedback improves bimanual force control performances at planning and execution levels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hyun Joon Kim ◽  
Joon Ho Lee ◽  
Nyeonju Kang ◽  
James H. Cauraugh
Keyword(s):  
Visual Feedback ◽  
Force Control ◽  
Maximum Voluntary Contraction ◽  
Correlation Coefficients ◽  
Uncontrolled Manifold ◽  
Force Variability ◽  
Motor Synergies ◽  
Multiple Trials ◽  
Motor Synergy ◽  
Force Accuracy

AbstractThe purpose of this study was to determine the effect of different visual conditions and targeted force levels on bilateral motor synergies and bimanual force control performances. Fourteen healthy young participants performed bimanual isometric force control tasks by extending their wrists and fingers under two visual feedback conditions (i.e., vision and no-vision) and three targeted force levels (i.e., 5%, 25%, and 50% of maximum voluntary contraction: MVC). To estimate bilateral motor synergies across multiple trials, we calculated the proportion of good variability relative to bad variability using an uncontrolled manifold analysis. To assess bimanual force control performances within a trial, we used the accuracy, variability, and regularity of total forces produced by two hands. Further, analysis included correlation coefficients between forces from the left and right hands. In addition, we examined the correlations between altered bilateral motor synergies and force control performances from no-vision to vision conditions for each targeted force level. Importantly, our findings revealed that the presence of visual feedback increased bilateral motor synergies across multiple trials significantly with a reduction of bad variability as well as improved bimanual force control performances within a trial based on higher force accuracy, lower force variability, less force regularity, and decreased correlation coefficients between hands. Further, we found two significant correlations in (a) increased bilateral motor synergy versus higher force accuracy at 5% of MVC and (b) increased bilateral motor synergy versus lower force variability at 50% of MVC. Together, these results suggested that visual feedback effectively improved both synergetic coordination behaviors across multiple trials and stability of task performance within a trial across various submaximal force levels.

scholarly journals Visual Feedback Improves Bimanual Force Control Performances at Planning and Execution Levels

2021 ◽  
Author(s):  
Hyun Joon Kim ◽  
Joon Ho Lee ◽  
Nyeonju Kang ◽  
James H. Cauraugh
Keyword(s):  
Visual Feedback ◽  
Force Control ◽  
Maximum Voluntary Contraction ◽  
Primary Outcome Measure ◽  
Voluntary Contraction ◽  
Uncontrolled Manifold ◽  
Motor Synergies ◽  
Uncontrolled Manifold Analysis ◽  
Multiple Trials ◽  
Coordination Patterns

Abstract The purpose of this study was to determine whether altered interlimb coordination patterns across trials improved bimanual force control capabilities within a trial. Fourteen healthy young participants completed bimanual force control tasks at 5%, 25%, and 50% of maximum voluntary contraction with and without visual feedback. To estimate synergetic coordination patterns between hands across multiple trials, we analyzed our primary outcome measure by performing an uncontrolled manifold analysis. In addition, we calculated force accuracy, variability, and regularity within a trial to quantify task stabilization. Using Pearson’s correlation analyses, we determined the relation between the changes in bilateral motor synergies (i.e., a proportion of good variability relative to bad variability) and bimanual force control performance from no-vision to vision conditions. The findings revealed that the presence of visual feedback significantly increased bilateral motor synergies with a reduction of bad variability components across multiple trials, and decreased force error, variability, and regularity within a trial. Further, we observed significant positive correlations between higher bilateral motor synergies and increased improvements in force control capabilities. These findings suggested that bimanual synergetic coordination behaviors at the planning level modulated by external sensory feedback may be related to advanced task stabilization patterns at the execution level.

scholarly journals Motor control theories and their applications

Medicina ◽  
2010 ◽  
Vol 46 (6) ◽  
pp. 382 ◽  
Author(s):  
Mark Latash ◽  
Mindy Levin ◽  
John Scholz ◽  
Gregor Schöner
Keyword(s):  
Motor Control ◽  
Equilibrium Point ◽  
Movement Disorders ◽  
Stretch Reflex ◽  
Uncontrolled Manifold ◽  
Uncontrolled Manifold Hypothesis ◽  
Equilibrium Point Hypothesis ◽  
Performance Variables ◽  
Neural Computations ◽  
Technical Details

We describe several infl uential hypotheses in the field of motor control including the equilibrium-point (referent confi guration) hypothesis, the uncontrolled manifold hypothesis, and the idea of synergies based on the principle of motor abundance. The equilibrium-point hypothesis is based on the idea of control with thresholds for activation of neuronal pools; it provides a framework for analysis of both voluntary and involuntary movements. In particular, control of a single muscle can be adequately described with changes in the threshold of motor unit recruitment during slow muscle stretch (threshold of the tonic stretch reflex). Unlike the ideas of internal models, the equilibrium-point hypothesis does not assume neural computations of mechanical variables. The uncontrolled manifold hypothesis is based on the dynamic system approach to movements; it offers a toolbox to analyze synergic changes within redundant sets of elements related to stabilization of potentially important performance variables. The referent confi guration hypothesis and the principle of abundance can be naturally combined into a single coherent scheme of control of multi-element systems. A body of experimental data on healthy persons and patients with movement disorders are reviewed in support of the mentioned hypotheses. In particular, movement disorders associated with spasticity are considered as consequences of an impaired ability to shift threshold of the tonic stretch reflex within the whole normal range. Technical details and applications of the mentioned hypo theses to studies of motor learning are described. We view the mentioned hypotheses as the most promising ones in the field of motor control, based on a solid physical and neurophysiological foundation.

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