scholarly journals Stabilization of cat paw trajectory during locomotion

2014 ◽  
Vol 112 (6) ◽  
pp. 1376-1391 ◽  
Author(s):  
Alexander N. Klishko ◽  
Bradley J. Farrell ◽  
Irina N. Beloozerova ◽  
Mark L. Latash ◽  
Boris I. Prilutsky
Keyword(s):  
Uncontrolled Manifold ◽  
Vertical Position ◽  
Components Of Variance ◽  
Performance Variables ◽  
Limb Segment ◽  
Orientation Space ◽  
Limb Kinematics ◽  
Locomotor Behaviors ◽  
Candidate Performance ◽  
Segment Orientation

We investigated which of cat limb kinematic variables during swing of regular walking and accurate stepping along a horizontal ladder are stabilized by coordinated changes of limb segment angles. Three hypotheses were tested: 1) animals stabilize the entire swing trajectory of specific kinematic variables (performance variables); and 2) the level of trajectory stabilization is similar between regular and ladder walking and 3) is higher for forelimbs compared with hindlimbs. We used the framework of the uncontrolled manifold (UCM) hypothesis to quantify the structure of variance of limb kinematics in the limb segment orientation space across steps. Two components of variance were quantified for each potential performance variable, one of which affected it (“bad variance,” variance orthogonal to the UCM, VORT) while the other one did not (“good variance,” variance within the UCM, VUCM). The analysis of five candidate performance variables revealed that cats during both locomotor behaviors stabilize 1) paw vertical position during the entire swing ( VUCM> VORT, except in mid-hindpaw swing of ladder walking) and 2) horizontal paw position in initial and terminal swing (except for the entire forepaw swing of regular walking). We also found that the limb length was typically stabilized in midswing, whereas limb orientation was not ( VUCM≤ VORT) for both limbs and behaviors during entire swing. We conclude that stabilization of paw position in early and terminal swing enables accurate and stable locomotion, while stabilization of vertical paw position in midswing helps paw clearance. This study is the first to demonstrate the applicability of the UCM-based analysis to nonhuman 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 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.

Estimation of lower limb segment orientation using Motion Envelopes: A preliminary study

2020 ◽  
Vol 81 ◽  
pp. 301-302
Author(s):  
I. Roupa ◽  
S.F. Paulo ◽  
S.B. Gonçalves ◽  
M. Tavares da Silva ◽  
D.S. Lopes
Keyword(s):  
Lower Limb ◽  
Limb Segment ◽  
Preliminary Study ◽  
Segment Orientation

scholarly journals Short-Term Effects of the Repeated Exposure to Trip-like Perturbations on Inter-Segment Coordination during Walking: An UCM Analysis

2021 ◽  
Vol 11 (20) ◽  
pp. 9663
Author(s):  
Vito Monaco ◽  
Clara Zabban ◽  
Tamon Miyake
Keyword(s):  
Lower Limb ◽  
Kinematic Chain ◽  
Repeated Exposure ◽  
Uncontrolled Manifold ◽  
Short Term ◽  
Motor Behaviors ◽  
Promising Tool ◽  
Limb Kinematics ◽  
Effective Organization ◽  
Short Term Effects

The minimum toe clearance (MTC) results from the coordination of all bilateral lower limb body segments, i.e., a redundant kinematic chain. We tested the hypothesis that repeated exposure to trip-like perturbations induces a more effective covariation of limb segments during steady walking, in accordance with the uncontrolled manifold (UCM) theory, to minimize the MTC across strides. Twelve healthy young adults (mean age 26.2 ± 3.3 years) were enrolled. The experimental protocol consisted of three identical trials, each involving three phases carried outin succession: steady walking (baseline), managing trip-like perturbations, and steady walking (post-perturbation). Lower limb kinematics collected during both steady walking phases wereanalyzed in the framework of the UCM theory to test the hypothesis that the reduced MTC variability following the perturbation can occur, in conjunction with more effective organization of the redundant lower limb segments. Results revealed that, after the perturbation, the synergy underlying lower limb coordination becomes stronger. Accordingly, the short-term effects of the repeated exposure to perturbations modify the organization of the redundant lower limb-related movements. In addition, results confirm that the UCM theory is a promising tool for exploring the effectiveness of interventions aimed at purposely modifying motor behaviors.

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.

scholarly journals Analysis of Lower Limb Segment Orientation Using Triaxial Accelerometers

2010 ◽  
Vol 5 (4) ◽  
pp. 368-379 ◽  
Author(s):  
Kun LIU ◽  
Yoshio INOUE ◽  
Kyoko SHIBATA
Keyword(s):  
Lower Limb ◽  
Limb Segment ◽  
Segment Orientation

scholarly journals Motor synergies research in physical therapy: advantages of the uncontrolled manifold approach

2017 ◽  
Vol 24 (1) ◽  
pp. 2-8 ◽  
Author(s):  
Daniela Virgínia Vaz
Keyword(s):  
Physical Therapy ◽  
Relevant Literature ◽  
Movement Control ◽  
Uncontrolled Manifold ◽  
Clinical Activity ◽  
Learning And Development ◽  
Literature Research ◽  
Performance Variables ◽  
Motor Synergies ◽  
Life Tasks

ABSTRACT Movement is central to physical therapy identity and practice. Advances in the science of movement control, motor learning and development are thus inextricably tied to professional development and clinical activity. This paper aims to describe a prominent approach to motor control with potential to greatly advance the understanding of movement dysfunction: the uncontrolled manifold (UCM). An argument is formulated for incorporating this method of data analysis in rehabilitation research. It is a narrative review of the relevant literature. Research in physical therapy could greatly benefit from investigating synergies with the theory and methods of UCM. Research should seek connections between functioning in daily life tasks and the assembling of synergies to stabilize different performance variables, the UCM variability measures, the synergy strength indexes, and the anticipatory synergy adjustments. Changes in these synergy variables should also be quantified after rehabilitation interventions. UCM can offer one solid science-based approach to inform clinical decisions on whether synergies have to be broken, rebalanced, created, or reinforced in patients with movement dysfunction.

scholarly journals Unpredictable elbow joint perturbation during reaching results in multijoint motor equivalence

2011 ◽  
Vol 106 (3) ◽  
pp. 1424-1436 ◽  
Author(s):  
D. J. S. Mattos ◽  
M. L. Latash ◽  
E. Park ◽  
J. Kuhl ◽  
J. P. Scholz
Keyword(s):  
Elbow Joint ◽  
Neural Control ◽  
Formal Method ◽  
General Scheme ◽  
Uncontrolled Manifold ◽  
Movement Trajectory ◽  
Motor Equivalence ◽  
Joint Configuration ◽  
Performance Variables ◽  
Hand Orientation

Motor equivalence expresses the idea that movement components reorganize in the face of perturbations to preserve the value of important performance variables, such as the hand's position in reaching. A formal method is introduced to evaluate this concept quantitatively: changes in joint configuration due to unpredictable elbow perturbation lead to a smaller change in performance variables than expected given the magnitude of joint configuration change. This study investigated whether motor equivalence was present during the entire movement trajectory and how magnitude of motor equivalence was affected by constraints imposed by two different target types. Subjects pointed to spherical and cylindrical targets both with and without an elbow joint perturbation produced by a low- or high-stiffness elastic band. Subjects' view of their arm was blocked in the initial position, and the perturbation condition was randomized to avoid prediction of the perturbation or its magnitude. A modification of the uncontrolled manifold method variance analysis was used to investigate how changes in joint configuration on perturbed vs. nonperturbed trials (joint deviation vector) affected the hand's position or orientation. Evidence for motor equivalence induced by the perturbation was present from the reach onset and increased with the strength of the perturbation after 40% of the reach, becoming more prominent as the reach progressed. Hand orientation was stabilized more strongly by motor equivalent changes in joint configuration than was three-dimensional position regardless of the target condition. Results are consistent with a recent model of neural control that allows for flexible patterns of joint coordination while resisting joint configuration deviations in directions that affect salient performance variables. The observations also fit a general scheme of synergic control with referent configurations defined across different levels of the motor hierarchy.

scholarly journals Movements that are both variable and optimal

2012 ◽  
Vol 34 (1) ◽  
pp. 5-13 ◽  
Author(s):  
Mark L. Latash
Keyword(s):  
Cost Function ◽  
Neural Control ◽  
Healthy Aging ◽  
Motor Coordination ◽  
Uncontrolled Manifold ◽  
Cost Functions ◽  
Secondary Tasks ◽  
Performance Variables ◽  
Neurophysiological Mechanisms ◽  
Atypical Development

AbstractThis brief review addresses two major aspects of the neural control of multi-element systems. First, theprinciple of abundance suggests that the central nervous system unites elements into synergies (co-variation ofelemental variables across trials quantified within the framework of the uncontrolled manifold hypothesis) that stabilizeimportant performance variables. Second, a novel method, analytical inverse optimization, has been introduced tocompute cost functions that define averaged across trials involvement of individual elements over a range of values oftask-specific performance variables. The two aspects reflect two features of motor coordination: (1) using variablesolutions that allow performing secondary tasks and stabilizing performance variables; and (2) selecting combinationsof elemental variables that follow an optimization principle. We suggest that the conflict between the two approaches (asingle solution vs. families of solutions) is apparent, not real. Natural motor variability may be due to using the samecost function across slightly different initial states; on the other hand, there may be variability in the cost function itselfleading to variable solutions that are all optimal with respect to slightly different cost functions. The analysis of motorsynergies has revealed specific changes associated with atypical development, healthy aging, neurological disorders, andpractice. These have allowed formulating hypotheses on the neurophysiological mechanisms involved in the synergiccontrol of actions.

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