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Uncontrolled manifold

Ali Falaki, Xuemei Huang, Mechelle M Lewis, Mark L Latash
We explored posture-stabilizing multi-muscle synergies with two methods of analysis of multi-element, abundant systems: (1) Analysis of inter-cycle variance; and (2) Analysis of motor equivalence, both quantified within the framework of the uncontrolled manifold (UCM) hypothesis. Data collected in two earlier studies of patients with Parkinson's disease (PD) were re-analyzed. One study compared synergies in the space of muscle modes (muscle groups with parallel scaling of activation) during tasks performed by early-stage PD patients and controls...
April 28, 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
P Passos, J Milho, C Button
Collective behaviors in team sports result in players forming interpersonal synergies that contribute to performance goals. Because of the huge amount of variables that continuously constrain players' behavior during a game, the way that these synergies are formed remain unclear. Our aim was to quantify interpersonal synergies in the team sport of Rugby Union. For that purpose we used the Uncontrolled Manifold Hypothesis (UCM) to identify interpersonal synergies that are formed between ball carrier and support player in two-versus-one situations in Rugby Union...
April 19, 2017: Behavior Research Methods
Amanda Marchini, Rafael Pereira, Wellington Pedroso, Evangelos Christou, Osmar Pinto Neto
Older adults are more variable than young adults on tasks that demand the simultaneous control of more than one effector, and the difference between age groups may be related to their different capacity of coordinating the force output of the involved effectors. The goal of this study was to determine whether age-associated differences in motor output variability during tasks involving the simultaneous dorsiflexion of two feet can be partially explained by differences in coordination and possibly attenuated by physical training...
April 19, 2017: Somatosensory & Motor Research
Christian Greve, Tibor Hortobágyi, Raoul M Bongers
PURPOSE: Our ability to flexibly coordinate the available degrees of freedom allows us to perform activities of daily living under various task constraints. Healthy old adults exhibit subclinical peripheral and central nervous system dysfunctions, possibly compromising the flexibility in inter-joint coordination during voluntary movements and the ability to adapt to varying task constraints. METHOD: We examined how healthy old (75.4 ± 5.2 years, n = 14) compared with young adults (24...
May 2017: European Journal of Applied Physiology
Nyeonju Kang, James H Cauraugh
Dysfunction in bilateral coordination post-stroke is responsible for impaired bilateral movements. This study examined bilateral synergies using the uncontrolled manifold (UCM) approach while individuals in a chronic stage after stroke executed bilateral isometric force control at three submaximal force levels. Nine patients with stroke and nine age-matched healthy controls performed 24 trials of wrist and fingers extension at 5, 25, and 50% of MVC. The UCM findings revealed: (a) decreased bilateral synergies in patients with stroke as compared to controls at 50% of MVC and (b) reduced good variability and increased bad variability components in patients with stroke at 50% of MVC...
February 28, 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Mark L Latash
Biomechanics and motor control are discussed as parts of a more general science, physics of living systems. Major problems of biomechanics deal with exact definition of variables and their experimental measurement. In motor control, major problems are associated with formulating currently unknown laws of nature specific for movements by biological objects. Mechanics-based hypotheses in motor control, such as those originating from notions of a generalized motor program and internal models, are non-physical...
September 1, 2016: Journal of Human Kinetics
Yun Wang, Kazuhiko Watanabe, Tadayoshi Asaka
PURPOSE: We explored changes in muscle interactions during healthy aging as a window into neural control strategies of postural preparation to action/perturbation. In particular, we quantified the strength of multi-muscle synergies stabilizing the center of pressure (COP) displacement during the preparation for making a step associated with support surface translations. METHODS: Young and elderly subjects were required to make a step in response to support surface perturbations...
December 21, 2016: European Journal of Applied Physiology
Yasuyuki Suzuki, Hiroki Morimoto, Ken Kiyono, Pietro G Morasso, Taishin Nomura
Human postural sway during stance arises from coordinated multi-joint movements. Thus, a sway trajectory represented by a time-varying postural vector in the multiple-joint-angle-space tends to be constrained to a low-dimensional subspace. It has been proposed that the subspace corresponds to a manifold defined by a kinematic constraint, such that the position of the center of mass (CoM) of the whole body is constant in time, referred to as the kinematic uncontrolled manifold (kinematic-UCM). A control strategy related to this hypothesis (CoM-control-strategy) claims that the central nervous system (CNS) aims to keep the posture close to the kinematic-UCM using a continuous feedback controller, leading to sway patterns that mostly occur within the kinematic-UCM, where no corrective control is exerted...
2016: Frontiers in Human Neuroscience
Daniele Piscitelli, Ali Falaki, Stanislaw Solnik, Mark L Latash
We explored two aspects of feed-forward postural control, anticipatory postural adjustments (APAs) and anticipatory synergy adjustments (ASAs) seen prior to self-triggered unloading with known and unknown direction of the perturbation. In particular, we tested two main hypotheses predicting contrasting changes in APAs and ASAs. The first hypothesis predicted no major changes in ASAs. The second hypothesis predicted delayed APAs with predominance of co-contraction patterns when perturbation direction was unknown...
March 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Behnoosh Parsa, Vladimir M Zatsiorsky, Mark L Latash
We address the nature of unintentional changes in performance in two papers. This second paper tested hypotheses related to stability of task-specific performance variables estimated using the framework of the uncontrolled manifold (UCM) hypothesis. Our first hypothesis was that selective stability of performance variables would be observed even when the magnitudes of those variables drifted unintentionally because of the lack of visual feedback. Our second hypothesis was that stability of a variable would depend on the number of explicit task constraints...
February 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Hang Jin Jo, Daniela Mattos, Elisabeth B Lucassen, Xuemei Huang, Mark L Latash
The authors explored the changes in multidigit synergies in patients with multiple sclerosis (MS) within the framework of the uncontrolled manifold hypothesis. The specific hypotheses were that both synergy indices and anticipatory synergy adjustments prior to the initiation of a self-paced quick action would be diminished in the patients compared to age-matched controls. The MS patients and age-matched controls (n = 13 in both groups) performed one-finger and multifinger force production tasks involving both accurate steady-state force production and quick force pulses...
August 11, 2016: Journal of Motor Behavior
Ingmar E J de Vries, Andreas Daffertshofer, Dick F Stegeman, Tjeerd W Boonstra
Neural synchrony has been suggested as a mechanism for integrating distributed sensorimotor systems involved in coordinated movement. To test the role of corticomuscular and intermuscular coherence in bimanual coordination, we experimentally manipulated the degree of coordination between hand muscles by varying the sensitivity of the visual feedback to differences in bilateral force. In 16 healthy participants, cortical activity was measured using EEG and muscle activity of the flexor pollicis brevis of both hands using high-density electromyography (HDsEMG)...
December 1, 2016: Journal of Neurophysiology
Sasha Reschechtko, Vladimir M Zatsiorsky, Mark L Latash
Manipulating objects with the hands requires the accurate production of resultant forces including shear forces; effective control of these shear forces also requires the production of internal forces normal to the surface of the object(s) being manipulated. In the present study, we investigated multi-finger synergies stabilizing shear and normal components of force, as well as drifts in both components of force, during isometric pressing tasks requiring a specific magnitude of shear force production. We hypothesized that shear and normal forces would evolve similarly in time and also show similar stability properties as assessed by the decomposition of inter-trial variance within the uncontrolled manifold hypothesis...
January 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Shunta Togo, Hiroshi Imamizu
We grasp and dexterously manipulate an object through multi-digit synergy. In the framework of the uncontrolled manifold (UCM) hypothesis, multi-digit synergy is defined as the coordinated control mechanism of fingers to stabilize variable important for task success, e.g., total force. Previous studies reported anticipatory synergy adjustments (ASAs) that correspond to a drop of the synergy index before a quick change of the total force. The present study compared ASA's properties with individual performances of feedforward force control to investigate a relationship of those...
October 6, 2016: Neuroscience Letters
Shunta Togo, Takahiro Kagawa, Yoji Uno
The brain must coordinate with redundant bodies to perform motion tasks. The aim of the present study is to propose a novel control model that predicts the characteristics of human joint coordination at a behavioral level. To evaluate the joint coordination, an uncontrolled manifold (UCM) analysis that focuses on the trial-to-trial variance of joints has been proposed. The UCM is a nonlinear manifold associated with redundant kinematics. In this study, we directly applied the notion of the UCM to our proposed control model called the "UCM reference feedback control...
2016: Frontiers in Computational Neuroscience
Megan E Toney, Young-Hui Chang
Human walking is a complex task, and we lack a complete understanding of how the neuromuscular system organizes its numerous muscles and joints to achieve consistent and efficient walking mechanics. Focused control of select influential task-level variables may simplify the higher-level control of steady-state walking and reduce demand on the neuromuscular system. As trailing leg power generation and force application can affect the mechanical efficiency of step-to-step transitions, we investigated how joint torques are organized to control leg force and leg power during human walking...
October 2016: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Stanislaw Solnik, Sasha Reschechtko, Yen-Hsun Wu, Vladimir M Zatsiorsky, Mark L Latash
We investigated multidigit synergies stabilizing components of the resultant force vector during joint performance of a static prehension task by two persons as compared to similar tasks performed by a single person using both hands. Subjects transferred the instrumented handle from the right hand to the left hand (one-person condition) or passed that handle to another person (two-person condition) while keeping the handle's position and orientation stationary. Only three digits were involved per hand, the thumb, the index finger, and the middle finger; the forces and moments produced by the digits were measured by six-component sensors...
August 2016: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Geetanjali Gera, Kelsey E McGlade, Darcy S Reisman, John Peter Scholz
In this study, we investigated deficits in coordination of trunk muscle modes involved in the stabilization of the trunk's trajectory for reaching upward and downward beyond functional arm length. Trunk muscle activity from 10 stroke survivors (8 men, 2 women; 64.1 ± 10.5 years old) and 9 healthy control subjects (7 men, 2 women; 59.3 ± 9.3 years old) was analyzed. Coordination of trunk muscle modes to stabilize the trunk trajectory was investigated using the uncontrolled manifold (UCM) analysis. The UCM analysis decomposes the variability of muscle modes into good and bad variability...
January 2016: Motor Control
Shraddha Srivastava, Pei-Chun Kao, Darcy S Reisman, Jill S Higginson, John P Scholz
The central nervous system (CNS) is believed to use the abundant degrees of freedom of muscles and joints to stabilize a particular task variable important for task success, such as footpath during walking. Stroke survivors often demonstrate impaired balance and high incidences of falls due to increased footpath variability during walking. In the current study, we use the uncontrolled manifold (UCM) approach to investigate the role of motor abundance in stabilizing footpath during swing phase in healthy individuals and stroke survivors...
July 2016: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Eunse Park, Hendrik Reimann, Gregor Schöner
The control of upright stance is commonly explained on the basis of the single inverted pendulum model (ankle strategy) or the double inverted pendulum model (combination of ankle and hip strategy). Kinematic analysis using the uncontrolled manifold (UCM) approach suggests, however, that stability in upright standing results from coordinated movement of multiple joints. This is based on evidence that postural sway induces more variance in joint configurations that leave the body position in space invariant than in joint configurations that move the body in space...
June 2016: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
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