Finger coordination in persons with Down syndrome: atypical patterns of coordination and the effects of practice

Latash, Mark L.; Kang, Ning; Patterson, David

doi:10.1007/s00221-002-1189-3

Cited by 102 publications

(82 citation statements)

References 28 publications

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“…Actually, commands to fingers (finger modes) showed predominantly positive co-variation across trials that could be viewed as contributing to total force variability. In earlier studies, such patterns of finger force co-variation were referred to as "the fork strategy", that is using the fingers as the prongs of a fork rather than exploiting the flexibility of the hand design (Latash et al 2002a;Scholz et al 2003). We have also observed substantial differences in finger coordination during the production of PR and SU moments of force.…”

Section: Discussionmentioning

confidence: 83%

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Finger synergies during multi-finger cyclic production of moment of force

2006

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We investigated multi-finger synergies stabilizing the total moment of force and the total force when the subjects produced a quick cyclic change in the total moment of force. The seated subjects performed the task with the fingers of the dominant arm while paced by the metronome at 1.33 Hz. They were required to produce a rhythmic, sine-like change in the total pronation-supination moment of force computed with respect to the midpoint between the middle and ring fingers. The framework of the uncontrolled manifold hypothesis was used to compute indices of stabilization of the total moment and of the total force across 20 cycles. Variance of the total moment showed a cyclic pattern with peaks close to the peak rate of the moment change. Variance of the total force was maximal close to peak moment into supination. Higher magnitudes of the moment directed against the required moment direction (antagonist moment) were produced by individual fingers during supination efforts as compared to pronation efforts. Indices of multi-finger synergies showed across-trials stabilization of the total moment over the whole cycle but not of the total force. These indices were smaller during supination efforts. We conclude that the central nervous system facilitates multi-finger synergies stabilizing the total rotational action across a variety of tasks. Synergies stabilizing the total force are not seen in tasks that do not explicitly require accurate force control. Pronation efforts are performed more efficiently and with better stabilization of the action.

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Section: Discussionmentioning

confidence: 83%

“…A series of recent studies investigated multi-finger synergies in a variety of isometric tasks that required the production of certain total force patterns (Latash et al 2001(Latash et al , 2002aScholz et al 2002). These studies used the framework of the uncontrolled manifold (UCM) hypothesis (Scholz and Schoner 1999).…”

Section: Introductionmentioning

confidence: 99%

Finger synergies during multi-finger cyclic production of moment of force

2006

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“…This hypothesis is supported by recent studies of finger force production tasks that report lower total force variance compared to the sum of variances of individual finger forces (Latash et al 2002c. More extensive evidence comes from additional studies of finger force production tasks (Latash et al 2001(Latash et al ,2002aScholz et al 2002Scholz et al ,2003Shinohara et al 2004), of upper extremity targeting tasks (Scholz et al 2000;Tseng et al 2002Tseng et al ,2003Tseng and Scholz 2005a,b) and of both kinematic (Krishnamoorthy et al 2005;Reisman et al 2002;Scholz et al 2001) and muscular synergies (Krishnamoorthy et al 2003(Krishnamoorthy et al ,2004 underlying postural control.…”

Section: Introductionmentioning

confidence: 70%

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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“…In one study , the framework of the UCM hypothesis was applied to the analysis of the multi-finger production of an accurate slow ramp profile of the total force while persons with Down syndrome (DS), aged 14 to 42, pressed on force sensors with all four fingers of the dominant hand (Latash et al, 2002b). Prior to practice, persons with DS showed predominantly positive covariation among individual finger forces (and modes) that destabilized the total force.…”

Section: Atypical Synergies In Down Syndromementioning

confidence: 99%