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Joint angle variability in 3D bimanual pointing: uncontrolled manifold analysis.
Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
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2005 (English)In: Experimental Brain Research, ISSN 0014-4819, Vol. 163, no 1, 44-57 p.Article in journal (Refereed) Published
Abstract [en]

The structure of joint angle variability and its changes with practice were investigated using the uncontrolled manifold (UCM) computational approach. Subjects performed fast and accurate bimanual pointing movements in 3D space, trying to match the tip of a pointer, held in the right hand, with the tip of one of three different targets, held in the left hand during a pre-test, several practice sessions and a post-test. The prediction of the UCM approach about the structuring of joint angle variance for selective stabilization of important task variables was tested with respect to selective stabilization of time series of the vectorial distance between the pointer and aimed target tips (bimanual control hypothesis) and with respect to selective stabilization of the endpoint trajectory of each arm (unimanual control hypothesis). The components of the total joint angle variance not affecting (V(COMP)) and affecting (V(UN)) the value of a selected task variable were computed for each 10% of the normalized movement time. The ratio of these two components R(V)=V(COMP)/V(UN) served as a quantitative index of selective stabilization. Both the bimanual and unimanual control hypotheses were supported, however the R(V) values for the bimanual hypothesis were significantly higher than those for the unimanual hypothesis applied to the left and right arm both prior to and after practice. This suggests that the CNS stabilizes the relative trajectory of one endpoint with respect to the other more than it stabilizes the trajectories of each of the endpoints in the external space. Practice-associated improvement in both movement speed and accuracy was accompanied by counter-intuitive lack of changes in R(V). Both V(COMP) and V(UN) variance components decreased such that their ratio remained constant prior to and after practice. We conclude that the UCM approach offers a unique and under-explored opportunity to track changes in the organization of multi-effector systems with practice and allows quantitative assessment of the degree of stabilization of selected performance variables.

Place, publisher, year, edition, pages
2005. Vol. 163, no 1, 44-57 p.
Keyword [en]
Adult, Arm/*physiology, Biomechanics/*methods/standards, Elbow Joint/physiology, Female, Finger Joint/physiology, Humans, Joints/*physiology, Models; Biological, Movement/*physiology, Reproducibility of Results, Shoulder Joint/physiology, Volition/physiology, Wrist Joint/physiology
URN: urn:nbn:se:umu:diva-16968PubMedID: 15668794OAI: diva2:156641
Available from: 2007-10-23 Created: 2007-10-23 Last updated: 2009-11-10Bibliographically approved
In thesis
1. Perception and control of upper limb movement: Insights gained by analysis of sensory and motor variability
Open this publication in new window or tab >>Perception and control of upper limb movement: Insights gained by analysis of sensory and motor variability
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Chronic neck-shoulder pain is associated with impairments of proprioception and motor control. Thus, assessment of proprioceptive and motor function may be powerful tools both for research and clinical practice. However, insufficient knowledge of certain features of human sensorimotor control hampers both development and interpretation of results of clinically relevant tests. For example, evidence is lacking which proprioception submodalities are reflected in common tests of proprioception. For testing motor function, a better understanding of the control of goal directed arm movements is needed. The purpose of the thesis was to gain further insights into the sensorimotor control of the upper limb in healthy subjects, with implications for clinical testing. The main aims were: (1) to study relationships of outcomes of different tests of shoulder proprioception and (2) to study control strategies in bimanual pointing tasks by analysis of the structure of joint angle variability with the Uncontrolled Manifold (UCM) method. Correlations between proprioceptive acuity in different variants of ipsilateral position-matching and velocity-discrimination were studied. The main finding was that two uncorrelated mechanisms based either on perception of position or movement might underlie perception of limb location in ipsilateral position-matching. The results provided important information for interpretation of common and development of novel tests of shoulder proprioception. The structure of joint angle variance was computed with respect to several task variables during bimanual pointing. Joint angle variability was decomposed in variance affecting and not affecting a task variable. The results showed that the variance in joint space was structured according to the predictions of the UCM hypothesis. It was also shown that the arms were united into one synergy to significantly larger degree than joints within each arm were united into single-arm synergies. It was concluded that the UCM approach might quantify components of motor variability during repetitive motor tasks.

Place, publisher, year, edition, pages
Umeå: Kirurgisk och perioperativ vetenskap, 2005. 51 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 953
Medicine, proprioception, kinaesthesia, position sense, movement sense, position-matching, velocity-discrimination, correlation, uncontrolled manifold, variability, synergy, upper limb, motor control, Medicin
National Category
Sport and Fitness Sciences
Research subject
urn:nbn:se:umu:diva-485 (URN)91-7305-850-5 (ISBN)
Public defence
2005-04-12, Stora salen, Arbetslivsinstitutet / Belastningsskadecentrum, Petrus Lästadius väg, Umeå, 13:00 (English)
Available from: 2005-03-31 Created: 2005-03-31 Last updated: 2015-01-21Bibliographically approved

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