Motor Control Strategies Revealed in the Structure of Motor Variability

Latash, Mark L.; Scholz, John P.; Schöner, Gregor

doi:10.1097/00003677-200201000-00006

Cited by 676 publications

(533 citation statements)

References 7 publications

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“…Although we can provide no direct evidence from this report that different points within a UCM correspond to different values of directional stiffness, this seems to be a reasonable assumption given endpoint stiffness estimates reported in earlier studies (Shadmehr et al 1993). The result is consistent with our view that variance in the values of movement components is not simply a reflection of noise (Latash et al 2002b;Scholz and Schöner 1999). …”

Section: Goal-equivalent Joint Configuration Variance Increased In Resupporting

confidence: 92%

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The role of kinematic redundancy in adaptation of reaching

2006

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Although important differences exist between learning a new motor skill and adapting a well-learned skill to new environmental constraints, studies of force field adaptation have been used frequently in recent years to identify processes underlying learning. Most of these studies have been of reaching tasks that were each hand position was specified by a unique combination of joint angles. At the same time, evidence has been provided from a variety of tasks that the central nervous system takes advantage of the redundancy available to it when planning and executing functional movements. The current study attempted to determine whether a change in the use of joint motion redundancy is associated with the adaptation process. Both experimental and control subjects performed 160 trials of reaching in each of four adaptation phases, while holding the handle of a robot manipulandum. During the first and last adaptation phases, the robot motors were turned off. During phases 2 and 3 the motors produced a velocity-dependent force field to which experimental subjects had to adapt to regain relatively straight line hand movements during reaching to a target, while the motors remained off for the control group. The uncontrolled manifold (UCM) method was used to partition the variance of planar clavicle-scapular, shoulder, elbow and wrist joint movements into two orthogonal components, one (V UCM ) that reflected combinations of joint angles that were equivalent with respect to achieving the average hand path and another (V ORT ) that took the hand away from its average path. There was no change in either variance component for the control group performing 640 nonperturbed reaches across four 'pseudo-adaptation' phases. The experimental group showed adaptation to reaching in the force field that was accompanied initially by an increase in both components of variance, followed by a smaller decrease of V UCM than V ORT during 320 practice reaches in the force field. After initial re-adaptation to reaching to the null field, V UCM was higher in experimental than in control subjects after performing a comparable number of reaches. V UCM was also larger in the experimental group after re-adaptation when compared to the 160 null field reaching trials performed prior to initial force field introduction. The results suggest that the central nervous system makes use of kinematic redundancy, or flexibility of motor patterns, to adapt reaching performance to unusual force fields, a fact that has implications for the hypothesis that motor adaptation requires learning of formal models of limb and environmental dynamics.

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Section: Goal-equivalent Joint Configuration Variance Increased In Resupporting

confidence: 92%

“…This principle emphasizes error compensation, or more generally, flexible solutions to the coordination of the motor elements underlying a motor task. Such flexibility may be the most important feature of a functional synergy (Latash et al 2002b). …”

Section: Introductionmentioning

confidence: 99%

The role of kinematic redundancy in adaptation of reaching

2006

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“…In the four-finger MVC pressing tasks it was found that the variance of the total maximal force output was smaller than the sum of variances of the maximal individual finger forces (Li et al 1998a(Li et al , 1998b. The reduction of the force variance at the multi-finger level suggested the existence of an inter-compensation among individual digits also confirmed in a series of further studies (Latash et al 2001(Latash et al , 2002a(Latash et al , 2002b. Santello and Soechting (2000) examined the control of five-digit grasping by measuring gripping forces when subjects lifted and held a handle.…”

Section: Multi-finger Synergies Stabilizing Force Directionmentioning

confidence: 87%

“…The existence of synergies in multi-finger force production is well documented and revealed in both pressing and grasping tasks (Li et al 1998a(Li et al , 1998bLatash et al 2001Latash et al , 2002aLatash et al , 2002b. In the four-finger MVC pressing tasks it was found that the variance of the total maximal force output was smaller than the sum of variances of the maximal individual finger forces (Li et al 1998a(Li et al , 1998b.…”

Section: Multi-finger Synergies Stabilizing Force Directionmentioning

confidence: 96%

“…This is a logical extension of a series of studies that analyzed multi-digit synergies in pressing and prehension tasks with respect to such performance variables as total force and total moment of forces produced by a set of digits (Latash et al 2001(Latash et al , 2002aShim et al 2003;Zatsiorsky and Latash 2004).…”

Section: To Test the Dependence Of Direction Accuracy On Target Forcementioning

confidence: 99%

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Control of finger force direction in the flexion-extension plane

2004

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We have examined the interaction among individual finger forces in tasks that required the production of the total force by a subset of fingers in a particular direction in the flexion-extension plane. Nine subjects produced fingertip forces in a prescribed direction with a maximum voluntary contraction (MVC) effort and held the peak force for two seconds. Six finger combinations were tested, four single-finger tasks-Index (I), Middle (M), Ring (R) and Little (L)-one two-digit task (IM), and one four-digit task (IMRL). The subjects were asked to generate the finger forces in two directions, 0° (perpendicular to the surface of the transducer) and 15° toward the palm. In all task conditions, there were two experimental sessions, with and without visual feedback on the task force vector. The main findings were:1. The target direction significantly affected the constant error (CE) but not the variable error (VE) while removal of the feedback resulted in an increase in VE. 2.The direction of the forces produced by fingers that were not explicitly required to produce force (enslaved fingers) depended on the target direction. 3.In multi-finger tasks, the individual fingers produced force in directions that could differ significantly from the target direction, while the resultant force pointed in the target direction. There was a negative co-variation among the deviations of the directions of the individual finger forces from the target direction. If a finger force vector deviated from the target, another finger force vector was likely to deviate in the opposite direction. We conclude that a multi-finger synergy is involved in the control of the finger force direction.

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How to Press a Button: Perspectives from the Science of Motor Control

Mattos

Frey

2018

Stevens' Handbook of Experimental Psychology and Cognitive Neuroscience

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Pressing a button in response to some stimulus is the most common response in all of experimental psychology. Yet, remarkably little attention has been paid to understanding the surprisingly complex processes that underlie this deceptively simple act. Here, we use the of pressing a response button as a vehicle for discussing some key theoretical and empirical developments in the study of motor control. Our hope is that readers will gain a fresh appreciation of the relevance of this area to investigations of perceptual and cognitive processes that employ motor responses.

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Motor Control Strategies Revealed in the Structure of Motor Variability

Cited by 676 publications

References 7 publications

The role of kinematic redundancy in adaptation of reaching

The role of kinematic redundancy in adaptation of reaching

Control of finger force direction in the flexion-extension plane

How to Press a Button: Perspectives from the Science of Motor Control

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