Dagmar Sternad - Academia.edu (original) (raw)
Papers by Dagmar Sternad
Abstract: This study investigates learning passive motor control strategies. Passive control is u... more Abstract: This study investigates learning passive motor control strategies. Passive control is understood as control without active error correction; the movement is stabilized by particular properties of the controlling dynamics. We analyze the task of juggling a ball on a racket. An approximation to the optimal solution of the task is derived by means of optimization theory. In order to model the learning process, the problem is coded for a genetic algorithm in representations without sensory or with sensory information.
Abstract: In the population model presented, an evolutionary dynamic is explored which is based o... more Abstract: In the population model presented, an evolutionary dynamic is explored which is based on the operator characteristics of genetic algorithms. Essential modification of genetic algorithms are dynamic boundary conditions and the inclusion of a constraint in the mixing of the gene pool. The pairing for crossover is governed by a selection principle based on a complementarity criterion derived from the theoretical tenet of perception-action mutuality of ecological psychology.
Behavioral and Brain Sciences, Jun 1, 1997
ABSTRACT
2014 40th Annual Northeast Bioengineering Conference (NEBEC), 2014
Motor Control, May 1, 2003
Http Dx Doi Org 10 1080 02701367 1998 10607704, Feb 8, 2013
Advances in Experimental Medicine and Biology, Feb 1, 2009
Http Dx Doi Org 10 1080 00222895 2010 536108, Nov 1, 2010
Physiotherapy, 2015
ABSTRACT To test the reliability and validity of shoulder joint angle measurements from the Micro... more ABSTRACT To test the reliability and validity of shoulder joint angle measurements from the Microsoft Kinect™ for virtual rehabilitation. Test-retest reliability and concurrent validity, feasibility study. Motion analysis laboratory. A convenience sample of 10 healthy adults. Shoulder joint angle was assessed in four static poses, two trials for each pose, using: (1) the Kinect; (2) a three-dimensional motion analysis system; and (3) a clinical goniometer. All poses were captured with the Kinect from the frontal view. The two poses of shoulder flexion were also captured with the Kinect from the sagittal view. Absolute and relative test-retest reliability of the Kinect for the measurement of shoulder angle was determined in each pose with intraclass correlation coefficients (ICCs), standard error of the measure and minimal detectable change. The 95% limits of agreement (LOA) between the Kinect and the standard methods for measuring shoulder angle were computed to determine concurrent validity. While the Kinect provided to be highly reliable (ICC 0.76-0.98) for measuring shoulder angle from the frontal view, the 95% LOA between the Kinect and the two measurement standards were greater than ±5° in all poses for both views. Before the Kinect is used to measure movements for virtual rehabilitation applications, it is imperative to understand its limitations in precision and accuracy for the measurement of specific joint motions. Copyright © 2015 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.
Motor control
... Login to save citations to My List. Citation. Database: PsycINFO. [Journal Article]. Effect o... more ... Login to save citations to My List. Citation. Database: PsycINFO. [Journal Article]. Effect of task and instruction on patterns of muscle activation: Wachholder and beyond. Sternad, Dagmar; Corcos, Daniel. Motor Control, Vol 5(4), Oct 2001, 307-336. Abstract. ...
We investigate the skill of rhythmically bouncing a ball on a racket with a focus on the mathemat... more We investigate the skill of rhythmically bouncing a ball on a racket with a focus on the mathematical modeling of the stability of performance. As a first step we derive the deterministic ball bouncing map as a Poincaré section of a sinusoidally driven bouncing ball. Subsequently, we show the ball bouncing map to have a passively stable regime. More precisely, for negative racket acceleration at impact, no control of racket amplitude or frequency is necessary for stable performance. Support for the model comes from a motor learning study, where a decrease in variability covaries with a change of mean acceleration at impact towards more negative values. For a more fine-grained test of the model we develop a stochastic version of it, by adding Gaussian white noise to the dynamics. We then test the model predictions for the correlation functions. We find that the observed correlation functions match the theoretical ones quite well, lending new support for the model. Lastly, we compare ...
Understanding Complex Systems, 2008
2014 40th Annual Northeast Bioengineering Conference (NEBEC), 2014
Motor control, 2003
An asymmetric bimanual task was investigated in which participants performed a rhythmic movement ... more An asymmetric bimanual task was investigated in which participants performed a rhythmic movement with their dominant arm and initiated a second movement with their nondominant arm at a random phase of the continued oscillations. The objective was to examine whether different constraints existed between rhythmic and discrete movements and, more generally, whether rhythmic and discrete movements can be regarded as two different movement primitives. Participants performed rhythmic forearm rotations at 1 of 4 prescribed metronome periods. After a random interval, a trigger signaled to initiate either a discrete or rhythmic movement with the left forearm as fast as possible while continuing the oscillations. Analyses extracted the mutual influences that the two movements exerted on each other and contrasted discrete-rhythmic and rhythmic-rhythmic coupling. (a) The initiation of the rhythmic movement was constrained to occur in-phase with the ongoing rhythmic movement, while the discrete ...
Experimental brain research, Jan 28, 2015
Feedback about error or reward is regarded essential for aiding learners to acquire a perceptual-... more Feedback about error or reward is regarded essential for aiding learners to acquire a perceptual-motor skill. Yet, when a task has redundancy and the mapping between execution and performance outcome is unknown, simple error feedback does not suffice in guiding the learner toward the optimal solutions. The present study developed and tested a new means of implicitly guiding learners to acquire a perceptual-motor skill, rhythmically bouncing a ball on a racket. Due to its rhythmic nature, this task affords dynamically stable solutions that are robust to small errors and noise, a strategy that is independent from actively correcting error. Based on the task model implemented in a virtual environment, a time-shift manipulation was designed to shift the range of ball-racket contacts that achieved dynamically stable solutions. In two experiments, subjects practiced with this manipulation that guided them to impact the ball with more negative racket accelerations, the indicator for the st...
Nature neuroscience, Jan 26, 2015
Abstract: This study investigates learning passive motor control strategies. Passive control is u... more Abstract: This study investigates learning passive motor control strategies. Passive control is understood as control without active error correction; the movement is stabilized by particular properties of the controlling dynamics. We analyze the task of juggling a ball on a racket. An approximation to the optimal solution of the task is derived by means of optimization theory. In order to model the learning process, the problem is coded for a genetic algorithm in representations without sensory or with sensory information.
Abstract: In the population model presented, an evolutionary dynamic is explored which is based o... more Abstract: In the population model presented, an evolutionary dynamic is explored which is based on the operator characteristics of genetic algorithms. Essential modification of genetic algorithms are dynamic boundary conditions and the inclusion of a constraint in the mixing of the gene pool. The pairing for crossover is governed by a selection principle based on a complementarity criterion derived from the theoretical tenet of perception-action mutuality of ecological psychology.
Behavioral and Brain Sciences, Jun 1, 1997
ABSTRACT
2014 40th Annual Northeast Bioengineering Conference (NEBEC), 2014
Motor Control, May 1, 2003
Http Dx Doi Org 10 1080 02701367 1998 10607704, Feb 8, 2013
Advances in Experimental Medicine and Biology, Feb 1, 2009
Http Dx Doi Org 10 1080 00222895 2010 536108, Nov 1, 2010
Physiotherapy, 2015
ABSTRACT To test the reliability and validity of shoulder joint angle measurements from the Micro... more ABSTRACT To test the reliability and validity of shoulder joint angle measurements from the Microsoft Kinect™ for virtual rehabilitation. Test-retest reliability and concurrent validity, feasibility study. Motion analysis laboratory. A convenience sample of 10 healthy adults. Shoulder joint angle was assessed in four static poses, two trials for each pose, using: (1) the Kinect; (2) a three-dimensional motion analysis system; and (3) a clinical goniometer. All poses were captured with the Kinect from the frontal view. The two poses of shoulder flexion were also captured with the Kinect from the sagittal view. Absolute and relative test-retest reliability of the Kinect for the measurement of shoulder angle was determined in each pose with intraclass correlation coefficients (ICCs), standard error of the measure and minimal detectable change. The 95% limits of agreement (LOA) between the Kinect and the standard methods for measuring shoulder angle were computed to determine concurrent validity. While the Kinect provided to be highly reliable (ICC 0.76-0.98) for measuring shoulder angle from the frontal view, the 95% LOA between the Kinect and the two measurement standards were greater than ±5° in all poses for both views. Before the Kinect is used to measure movements for virtual rehabilitation applications, it is imperative to understand its limitations in precision and accuracy for the measurement of specific joint motions. Copyright © 2015 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.
Motor control
... Login to save citations to My List. Citation. Database: PsycINFO. [Journal Article]. Effect o... more ... Login to save citations to My List. Citation. Database: PsycINFO. [Journal Article]. Effect of task and instruction on patterns of muscle activation: Wachholder and beyond. Sternad, Dagmar; Corcos, Daniel. Motor Control, Vol 5(4), Oct 2001, 307-336. Abstract. ...
We investigate the skill of rhythmically bouncing a ball on a racket with a focus on the mathemat... more We investigate the skill of rhythmically bouncing a ball on a racket with a focus on the mathematical modeling of the stability of performance. As a first step we derive the deterministic ball bouncing map as a Poincaré section of a sinusoidally driven bouncing ball. Subsequently, we show the ball bouncing map to have a passively stable regime. More precisely, for negative racket acceleration at impact, no control of racket amplitude or frequency is necessary for stable performance. Support for the model comes from a motor learning study, where a decrease in variability covaries with a change of mean acceleration at impact towards more negative values. For a more fine-grained test of the model we develop a stochastic version of it, by adding Gaussian white noise to the dynamics. We then test the model predictions for the correlation functions. We find that the observed correlation functions match the theoretical ones quite well, lending new support for the model. Lastly, we compare ...
Understanding Complex Systems, 2008
2014 40th Annual Northeast Bioengineering Conference (NEBEC), 2014
Motor control, 2003
An asymmetric bimanual task was investigated in which participants performed a rhythmic movement ... more An asymmetric bimanual task was investigated in which participants performed a rhythmic movement with their dominant arm and initiated a second movement with their nondominant arm at a random phase of the continued oscillations. The objective was to examine whether different constraints existed between rhythmic and discrete movements and, more generally, whether rhythmic and discrete movements can be regarded as two different movement primitives. Participants performed rhythmic forearm rotations at 1 of 4 prescribed metronome periods. After a random interval, a trigger signaled to initiate either a discrete or rhythmic movement with the left forearm as fast as possible while continuing the oscillations. Analyses extracted the mutual influences that the two movements exerted on each other and contrasted discrete-rhythmic and rhythmic-rhythmic coupling. (a) The initiation of the rhythmic movement was constrained to occur in-phase with the ongoing rhythmic movement, while the discrete ...
Experimental brain research, Jan 28, 2015
Feedback about error or reward is regarded essential for aiding learners to acquire a perceptual-... more Feedback about error or reward is regarded essential for aiding learners to acquire a perceptual-motor skill. Yet, when a task has redundancy and the mapping between execution and performance outcome is unknown, simple error feedback does not suffice in guiding the learner toward the optimal solutions. The present study developed and tested a new means of implicitly guiding learners to acquire a perceptual-motor skill, rhythmically bouncing a ball on a racket. Due to its rhythmic nature, this task affords dynamically stable solutions that are robust to small errors and noise, a strategy that is independent from actively correcting error. Based on the task model implemented in a virtual environment, a time-shift manipulation was designed to shift the range of ball-racket contacts that achieved dynamically stable solutions. In two experiments, subjects practiced with this manipulation that guided them to impact the ball with more negative racket accelerations, the indicator for the st...
Nature neuroscience, Jan 26, 2015