Journal of motor behavior
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Journal of motor behavior · Sep 2008
Comparative StudyAdaptation to a nonlinear visuomotor amplitude transformation with continuous and terminal visual feedback.
The control of a cursor on a computer monitor offers a simple means of exploring the limits of the plasticity of human visuomotor coordination. The authors explored the boundary conditions for adaptation to nonlinear visuomotor amplitude transformations. The authors hypothesized that only with terminal visual feedback during practice, but not with continuous visual feedback, humans might develop an internal model of the nonlinear visuomotor amplitude transformation. ⋯ In contrast to expectations, adaptive shifts and aftereffects observed in visual open-loop tests were linearly related to target amplitudes for both groups. Although the 2 feedback groups did not differ with respect to adaptive shifts and aftereffects, terminal visual feedback resulted in stable visual open-loop performance for an extended period, whereas movement errors increased after continuous visual feedback during practice. The benefit of continuous visual feedback, on the other hand, was faster closed-loop performance, indicating an optimization of visual closed-loop control.
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Journal of motor behavior · Sep 2005
From egocentric to exocentric spatial orientation: development of posture control in bimanual and trunk inclination tasks.
The authors investigated the emergence of independent control of body segments in bimanual tasks involving either voluntary or involuntary trunk motion by tracking the transition from an ego- to an exocentric mode of postural control during childhood (i.e., from body-referenced orientation to externally referenced action). A paradigm combining a seated manual task and various trunk manipulations described the coordination strategies used by 24 children at different ages (2 to 9 years) and by adults. ⋯ Young children patterned the forearm trajectory after the initiating segment (support surface or the trunk), thus reducing the degrees of freedom during the dual task. Echoing previous reports, 7-9 years of age appears to be a critical period in which children master postural control and develop an internal representation of body scheme.
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The authors review studies of mentally simulated movements. In automatic or cyclical movements, actual and motor imagery (MI) durations are similar. When athletes simulate only dynamic phases of movement or perform MI just before competing, however, environmental and time constraints lead to an underestimation of actual duration. ⋯ Results showed systematic and disproportionate overestimation of actual duration. The authors found a relationship between complex motor skills and MI duration. They discuss the factors leading to over- and underestimation and the hypotheses that could be tested.
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Journal of motor behavior · Mar 2004
Form and variability during sit-to-stand transitions: children versus adults.
In performing the sit-to-stand transition, young children (6- to 7-year-olds) were expected to display a movement form similar to that of adults. However, movement consistency was predicted to be poorer in children than in adults because they lack refinement of motor control processes. Kinematic analysis of 10 repetitions of the sit-to-stand movement was carried out for 6 typically developing children and 6 adults. ⋯ The authors interpret the children's lack of movement consistency as a reflection of inadequate stabilization of an internal model of intersegmental dynamics. Whereas adults have attained a skill level associated with refinement of that model, children have not. Children have an additional control problem because changes in body morphology throughout childhood require ongoing updating of the internal model that controls intrinsic dynamics.
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Journal of motor behavior · Jun 2002
Quiet eye duration, expertise, and task complexity in near and far aiming tasks.
. Skilled (n = 12) and less skilled (n = 12) billiards players participated in 2 experiments in which the relationship between quiet eye duration, expertise, and task complexity was examined in a near and a far aiming task. Quiet eye was defined as the final fixation on the target prior to the initiation of movement. ⋯ In Experiment 2, participants executed shots under 3 different time-constrained conditions in which quiet eye periods were experimentally manipulated. Shorter quiet eye periods resulted in poorer performance, irrespective of participant skill level. The authors argue that quiet eye duration represents a critical period for movement programming in the aiming response.