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Stability of Phase Relationships While Coordinating Arm Reaches with Whole Body Motion.

Bakker RS, Selen LP, Medendorp WP - PLoS ONE (2015)

Bottom Line: For parallel reaches, we found a stable in-phase and an unstable anti-phase relationship.For orthogonal reaches, we did not find a clear difference in stability between in-phase and anti-phase relationships.Computer simulations further show that cost models that minimize energy expenditure (i.e. net torques) or endpoint variance of the reach cannot fully explain the observed coordination patterns.

View Article: PubMed Central - PubMed

Affiliation: Radboud University Nijmegen, Donders Centre for Cognition, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.

ABSTRACT
The human movement repertoire is characterized by the smooth coordination of several body parts, including arm movements and whole body motion. The neural control of this coordination is quite complex because the various body parts have their own kinematic and dynamic properties. Behavioral inferences about the neural solution to the coordination problem could be obtained by examining the emerging phase relationship and its stability. Here, we studied the phase relationships that characterize the coordination of arm-reaching movements with passively-induced whole-body motion. Participants were laterally translated using a vestibular chair that oscillated at a fixed frequency of 0.83 Hz. They were instructed to reach between two targets that were aligned either parallel or orthogonal to the whole body motion. During the first cycles of body motion, a metronome entrained either an in-phase or an anti-phase relationship between hand and body motion, which was released at later cycles to test phase stability. Results suggest that inertial forces play an important role when coordinating reaches with cyclic whole-body motion. For parallel reaches, we found a stable in-phase and an unstable anti-phase relationship. When the latter was imposed, it readily transitioned or drifted back toward an in-phase relationship at cycles without metronomic entrainment. For orthogonal reaches, we did not find a clear difference in stability between in-phase and anti-phase relationships. Computer simulations further show that cost models that minimize energy expenditure (i.e. net torques) or endpoint variance of the reach cannot fully explain the observed coordination patterns. We discuss how predictive control and impedance control processes could be considered important mechanisms underlying the rhythmic coordination of arm reaches and body motion.

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Experimental setup and paradigms.(A) Subjects were seated on a linear sled and performed right hand reaching movements to visual targets presented on a sled mounted table. (B) Parallel reaching. (top) in-phase, (bottom) anti-phase. (C) Orthogonal reaching. (top) in-phase, (bottom) anti-phase.
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pone.0146231.g001: Experimental setup and paradigms.(A) Subjects were seated on a linear sled and performed right hand reaching movements to visual targets presented on a sled mounted table. (B) Parallel reaching. (top) in-phase, (bottom) anti-phase. (C) Orthogonal reaching. (top) in-phase, (bottom) anti-phase.

Mentions: Subjects were translated on linear sled (Fig 1A). The sled, powered by a linear motor (TB15N, Technotion, Almelo, The Netherlands), was controlled by a Kollmorgen S700 drive (Danaher, Washington, DC) with accuracy better than 0.034 mm, 2 mm/s, and 150 mm/s2. During the experiment, the sled moved sinusoidally at a fixed frequency of 0.8 Hz over 30 cm with a maximum acceleration of 4.1 m/s2. Subjects were seated with their interaural axis aligned with the direction of the sled motion. They were restrained with a five-point seat belt and the head was firmly fixed with an ear-fixed mold and a chin rest. Auditory stimuli were presented using in-ear headphones. Emergency buttons at either side of the chair could immediately stop the sled motion, if needed.


Stability of Phase Relationships While Coordinating Arm Reaches with Whole Body Motion.

Bakker RS, Selen LP, Medendorp WP - PLoS ONE (2015)

Experimental setup and paradigms.(A) Subjects were seated on a linear sled and performed right hand reaching movements to visual targets presented on a sled mounted table. (B) Parallel reaching. (top) in-phase, (bottom) anti-phase. (C) Orthogonal reaching. (top) in-phase, (bottom) anti-phase.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697800&req=5

pone.0146231.g001: Experimental setup and paradigms.(A) Subjects were seated on a linear sled and performed right hand reaching movements to visual targets presented on a sled mounted table. (B) Parallel reaching. (top) in-phase, (bottom) anti-phase. (C) Orthogonal reaching. (top) in-phase, (bottom) anti-phase.
Mentions: Subjects were translated on linear sled (Fig 1A). The sled, powered by a linear motor (TB15N, Technotion, Almelo, The Netherlands), was controlled by a Kollmorgen S700 drive (Danaher, Washington, DC) with accuracy better than 0.034 mm, 2 mm/s, and 150 mm/s2. During the experiment, the sled moved sinusoidally at a fixed frequency of 0.8 Hz over 30 cm with a maximum acceleration of 4.1 m/s2. Subjects were seated with their interaural axis aligned with the direction of the sled motion. They were restrained with a five-point seat belt and the head was firmly fixed with an ear-fixed mold and a chin rest. Auditory stimuli were presented using in-ear headphones. Emergency buttons at either side of the chair could immediately stop the sled motion, if needed.

Bottom Line: For parallel reaches, we found a stable in-phase and an unstable anti-phase relationship.For orthogonal reaches, we did not find a clear difference in stability between in-phase and anti-phase relationships.Computer simulations further show that cost models that minimize energy expenditure (i.e. net torques) or endpoint variance of the reach cannot fully explain the observed coordination patterns.

View Article: PubMed Central - PubMed

Affiliation: Radboud University Nijmegen, Donders Centre for Cognition, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.

ABSTRACT
The human movement repertoire is characterized by the smooth coordination of several body parts, including arm movements and whole body motion. The neural control of this coordination is quite complex because the various body parts have their own kinematic and dynamic properties. Behavioral inferences about the neural solution to the coordination problem could be obtained by examining the emerging phase relationship and its stability. Here, we studied the phase relationships that characterize the coordination of arm-reaching movements with passively-induced whole-body motion. Participants were laterally translated using a vestibular chair that oscillated at a fixed frequency of 0.83 Hz. They were instructed to reach between two targets that were aligned either parallel or orthogonal to the whole body motion. During the first cycles of body motion, a metronome entrained either an in-phase or an anti-phase relationship between hand and body motion, which was released at later cycles to test phase stability. Results suggest that inertial forces play an important role when coordinating reaches with cyclic whole-body motion. For parallel reaches, we found a stable in-phase and an unstable anti-phase relationship. When the latter was imposed, it readily transitioned or drifted back toward an in-phase relationship at cycles without metronomic entrainment. For orthogonal reaches, we did not find a clear difference in stability between in-phase and anti-phase relationships. Computer simulations further show that cost models that minimize energy expenditure (i.e. net torques) or endpoint variance of the reach cannot fully explain the observed coordination patterns. We discuss how predictive control and impedance control processes could be considered important mechanisms underlying the rhythmic coordination of arm reaches and body motion.

Show MeSH
Related in: MedlinePlus