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https://www.readbyqxmd.com/read/28338400/systematic-unintended-drifts-in-the-cyclic-force-produced-with-the-fingertips
#1
Satyajit Ambike, Daniela Mattos, Vladimir Zatsiorsky, Mark Latash
Cyclic isometric finger-force patterns established using visual feedback show systematic drifts when the feedback is removed. Force changes at multiple time scales and in opposite directions have been reported. For further characterization of these drifts, healthy subjects produced isometric, cyclic finger force with and without visual feedback at various initial amplitudes and frequencies. We hypothesized that on feedback removal, the amplitude will be attracted toward a preferred value that is frequency dependent...
January 1, 2018: Motor Control
https://www.readbyqxmd.com/read/27785549/optimality-and-stability-of-intentional-and-unintentional-actions-i-origins-of-drifts-in-performance
#2
Behnoosh Parsa, Alexander Terekhov, Vladimir M Zatsiorsky, Mark L Latash
We address the nature of unintentional changes in performance in two papers. This first paper tested a hypothesis that unintentional changes in performance variables during continuous tasks without visual feedback are due to two processes. First, there is a drift of the referent coordinate for the salient performance variable toward the actual coordinate of the effector. Second, there is a drift toward minimum of a cost function. We tested this hypothesis in four-finger isometric pressing tasks that required the accurate production of a combination of total moment and total force with natural and modified finger involvement...
February 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/27778048/optimality-and-stability-of-intentional-and-unintentional-actions-ii-motor-equivalence-and-structure-of-variance
#3
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
https://www.readbyqxmd.com/read/27601252/the-synergic-control-of-multi-finger-force-production-stability-of-explicit-and-implicit-task-components
#4
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
https://www.readbyqxmd.com/read/27540726/unsteady-steady-states-central-causes-of-unintentional-force-drift
#5
Satyajit Ambike, Daniela Mattos, Vladimir M Zatsiorsky, Mark L Latash
We applied the theory of synergies to analyze the processes that lead to unintentional decline in isometric fingertip force when visual feedback of the produced force is removed. We tracked the changes in hypothetical control variables involved in single fingertip force production based on the equilibrium-point hypothesis, namely the fingertip referent coordinate (RFT ) and its apparent stiffness (CFT ). The system's state is defined by a point in the {RFT ; CFT } space. We tested the hypothesis that, after visual feedback removal, this point (1) moves along directions leading to drop in the output fingertip force, and (2) has even greater motion along directions that leaves the force unchanged...
December 2016: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/27254391/analytical-inverse-optimization-in-two-hand-prehensile-tasks
#6
Behnoosh Parsa, Satyajit Ambike, Alexander Terekhov, Vladimir M Zatsiorsky, Mark L Latash
The authors explored application of analytical inverse optimization (ANIO) method to the normal finger forces in unimanual and bimanual prehensile tasks with discrete and continuously changing constraints. The subjects held an instrumented handle vertically with one or two hands. The external torque and grip force changed across trials or within a trial continuously. Principal component analysis showed similar percentages of variance accounted for by the first two principal components across tasks and conditions...
September 2016: Journal of Motor Behavior
https://www.readbyqxmd.com/read/27193319/on-the-nature-of-unintentional-action-a-study-of-force-moment-drifts-during-multifinger-tasks
#7
Behnoosh Parsa, Daniel J O'Shea, Vladimir M Zatsiorsky, Mark L Latash
We explored the origins of unintentional changes in performance during accurate force production in isometric conditions seen after turning visual feedback off. The idea of control with referent spatial coordinates suggests that these phenomena could result from drifts of the referent coordinate for the effector. Subjects performed accurate force/moment production tasks by pressing with the fingers of a hand on force sensors. Turning the visual feedback off resulted in slow drifts of both total force and total moment to lower magnitudes of these variables; these drifts were more pronounced in the right hand of the right-handed subjects...
August 1, 2016: Journal of Neurophysiology
https://www.readbyqxmd.com/read/27021074/interpersonal-synergies-static-prehension-tasks-performed-by-two-actors
#8
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
https://www.readbyqxmd.com/read/26974715/dynamic-parameter-identification-of-subject-specific-body-segment-parameters-using-robotics-formalism-case-study-head-complex
#9
Miguel Díaz-Rodríguez, Angel Valera, Alvaro Page, Antonio Besa, Vicente Mata
Accurate knowledge of body segment inertia parameters (BSIP) improves the assessment of dynamic analysis based on biomechanical models, which is of paramount importance in fields such as sport activities or impact crash test. Early approaches for BSIP identification rely on the experiments conducted on cadavers or through imaging techniques conducted on living subjects. Recent approaches for BSIP identification rely on inverse dynamic modeling. However, most of the approaches are focused on the entire body, and verification of BSIP for dynamic analysis for distal segment or chain of segments, which has proven to be of significant importance in impact test studies, is rarely established...
May 2016: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/26867493/the-pro-inflammatory-effects-of-mir-155-promote-liver-fibrosis-and-alcohol-induced-steatohepatitis
#10
Shashi Bala, Timea Csak, Banishree Saha, James Zatsiorsky, Karen Kodys, Donna Catalano, Abhishek Satishchandran, Gyongyi Szabo
BACKGROUND & AIMS: Alcoholic liver disease (ALD) ranges from fatty liver to inflammation and cirrhosis. miRNA-155 is an important regulator of inflammation. In this study, we describe the in vivo role of miR-155 in ALD. METHODS: Wild-type (WT) (C57/BL6J) or miR-155 knockout (KO) and TLR4 KO mice received Lieber DeCarli diet for 5weeks. Some mice received corn oil or CCl4 for 2 or 9weeks. RESULTS: We found that miR-155 KO mice are protected from alcohol-induced steatosis and inflammation...
June 2016: Journal of Hepatology
https://www.readbyqxmd.com/read/26701299/synergies-in-the-space-of-control-variables-within-the-equilibrium-point-hypothesis
#11
S Ambike, D Mattos, V M Zatsiorsky, M L Latash
We use an approach rooted in the recent theory of synergies to analyze possible co-variation between two hypothetical control variables involved in finger force production based on the equilibrium-point (EP) hypothesis. These control variables are the referent coordinate (R) and apparent stiffness (C) of the finger. We tested a hypothesis that inter-trial co-variation in the {R; C} space during repeated, accurate force production trials stabilizes the fingertip force. This was expected to correspond to a relatively low amount of inter-trial variability affecting force and a high amount of variability keeping the force unchanged...
February 19, 2016: Neuroscience
https://www.readbyqxmd.com/read/26434623/task-specific-stability-of-abundant-systems-structure-of-variance-and-motor-equivalence
#12
D Mattos, G Schöner, V M Zatsiorsky, M L Latash
Our main goal was to test a hypothesis that transient changes in performance of a steady-state task would result in motor equivalence. We also estimated effects of visual feedback on the amount of reorganization of motor elements. Healthy subjects performed two variations of a four-finger pressing task requiring accurate production of total pressing force (F TOT) and total moment of force (M TOT). In the Jumping-Target task, a sequence of target jumps required transient changes in either F TOT or M TOT. In the Step-Perturbation task, the index finger was lifted by 1cm for 0...
December 3, 2015: Neuroscience
https://www.readbyqxmd.com/read/26419663/the-nature-of-constant-and-cyclic-force-production-unintentional-force-drift-characteristics
#13
Satyajit Ambike, Daniela Mattos, Vladimir M Zatsiorsky, Mark L Latash
We explored unintentional changes in forces during performance of constant and cyclic force-production tasks (F-tasks) after visual feedback removal. Based on earlier studies, we expected all force parameters to drop exponentially with time. We also explored possible role of working memory in the force drop phenomena. Healthy subjects performed constant or cyclic isometric F-tasks with the index finger under visual feedback. The cyclic task was paced by a metronome. Removing visual feedback resulted in a consistent force drop in constant F-tasks and a qualitatively similar drift in the mean force in the cyclic F-task...
January 2016: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/26169103/unintentional-changes-in-the-apparent-stiffness-of-the-multi-joint-limb
#14
Tao Zhou, Vladimir M Zatsiorsky, Mark L Latash
We explored the phenomenon of unintentional changes in the apparent stiffness of the human arm produced by transient changes in the external force. The subjects performed a positional task against a constant baseline force and were instructed not to react to changes in the force. A HapticMaster robot produced a smooth force increase (a perturbation) leading to a hand movement, followed by a dwell time. No visible hand drift was observed during the dwell time. After the robot force dropped to its initial baseline value, the hand moved toward the initial position but stopped short of it...
October 2015: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/26105756/force-stabilizing-synergies-in-motor-tasks-involving-two-actors
#15
Stanislaw Solnik, Sasha Reschechtko, Yen-Hsun Wu, Vladimir M Zatsiorsky, Mark L Latash
We investigated the ability of two persons to produce force-stabilizing synergies in accurate multi-finger force production tasks under visual feedback on the total force only. The subjects produced a time profile of total force (the sum of two hand forces in one-person tasks and the sum of two subject forces in two-person tasks) consisting of a ramp-up, steady-state, and ramp-down segments; the steady-state segment was interrupted in the middle by a quick force pulse. Analyses of the structure of inter-trial finger force variance, motor equivalence, anticipatory synergy adjustments (ASAs), and the unintentional drift of the sharing pattern were performed...
October 2015: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/26000460/estimating-physical-activity-energy-expenditure-with-the-kinect-sensor-in-an-exergaming-environment
#16
David Nathan, Du Q Huynh, Jonas Rubenson, Michael Rosenberg
Active video games that require physical exertion during game play have been shown to confer health benefits. Typically, energy expended during game play is measured using devices attached to players, such as accelerometers, or portable gas analyzers. Since 2010, active video gaming technology incorporates marker-less motion capture devices to simulate human movement into game play. Using the Kinect Sensor and Microsoft SDK this research aimed to estimate the mechanical work performed by the human body and estimate subsequent metabolic energy using predictive algorithmic models...
2015: PloS One
https://www.readbyqxmd.com/read/25896800/moving-a-hand-held-object-reconstruction-of-referent-coordinate-and-apparent-stiffness-trajectories
#17
S Ambike, T Zhou, V M Zatsiorsky, M L Latash
This study used the framework of the referent configuration hypothesis and slow changes in the external conditions during vertical oscillation of a hand-held object to infer the characteristics of hypothetical control variables. The study had two main objectives: (1) to show that hypothetical control variables, namely, referent coordinates and apparent stiffness of vertical hand position and grip force can be measured in an experiment; and (2) to establish relation(s) between these control variables that yield the classic grip-force-load-force coupling...
July 9, 2015: Neuroscience
https://www.readbyqxmd.com/read/25565327/task-specific-stability-of-multifinger-steady-state-action
#18
Sasha Reschechtko, Vladimir M Zatsiorsky, Mark L Latash
The authors explored task-specific stability during accurate multifinger force production tasks with different numbers of instructed fingers. Subjects performed steady-state isometric force production tasks and were instructed not to interfere voluntarily with transient lifting-and-lowering perturbations applied to the index finger. The main results were (a) intertrial variance in the space of finger modes at steady states was larger within the subspace that had no effect on the total force (the uncontrolled manifold [UCM]); (b) perturbations caused large deviations of finger modes within the UCM (motor equivalence); and (c) deviations caused by the perturbation showed larger variance within the UCM...
2015: Journal of Motor Behavior
https://www.readbyqxmd.com/read/25417192/processes-underlying-unintentional-finger-force-changes-in-the-absence-of-visual-feedback
#19
Satyajit Ambike, Vladimir M Zatsiorsky, Mark L Latash
Previous reports show that the forces produced by the fingers of one hand drop exponentially over time in the absence of visual feedback on the forces. We study the force production by the index fingers of both hands with no visual feedback. Subjects produced a specified total force with a specific contribution from each finger by pressing on force sensors. We observed that in the absence of visual feedback: (1) The finger forces dropped with time by an amount proportional to the magnitude of the initial force...
March 2015: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/25365477/learning-to-combine-high-variability-with-high-precision-lack-of-transfer-to-a-different-task
#20
Yen-Hsun Wu, Thomas S Truglio, Vladimir M Zatsiorsky, Mark L Latash
The authors studied effects of practicing a 4-finger accurate force production task on multifinger coordination quantified within the uncontrolled manifold hypothesis. During practice, task instability was modified by changing visual feedback gain based on accuracy of performance. The authors also explored the retention of these effects, and their transfer to a prehensile task. Subjects practiced the force production task for 2 days. After the practice, total force variability decreased and performance became more accurate...
2015: Journal of Motor Behavior
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