Planning and execution of multijoint movements

Hogan, Neville

doi:10.1139/y88-080

Cited by 105 publications

(38 citation statements)

References 18 publications

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“…It now seems well accepted that we plan a limb movement in space coordinates (Hogan, 1988;Morasso, 1981). However, it is still an open question as to what type of coding is used in the planning and execution of goaldirected movements.…”

Section: Discussionmentioning

confidence: 99%

Vector coding in slow goal-directed arm movements

Graaf

Gon

Sittig

1996

Perception & Psychophysics

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It has been found that the estimate of relative target direction is consistently biased. Relative target direction refers to the direction in which a target is located relative to another location in space (e.g., a starting position in the case of goal-directed movements). In this study, we have tested two models that could underlie this biased estimate. The first proposed model is based on a distorted internal representation of locations (i.e., we perceive a target at the "wrong" location). Wecall this the distorted location model. The second model is based on the idea that the derivation of target direction from spatial information about starting and target position is biased. Wecall this the biased direction model. These two models lead to different predictions of the deviations that occur when the distance between the starting position and the target position is increased. Since we know from previous studies that the initial direction of slow arm movements reflects the target direction estimate, we tested the two models by analyzing the initial direction of slow arm movements. The results show that the biased direction model can account for the biases we find in the target direction estimate for various target distances, whereas the distorted location model cannot. In two additional experiments, we explored this model further. The results show that the biases depend only on the orientation of the line through starting position and target position relative to the plane through longitudinal head or body axis and starting position. Weconclude that the initial part of (slow) goal-directed arm movements is planned on the basis of a (biased) target direction estimate and not on the basis of a wrong internal representation of target location. This supports the hypothesis that we code displacements of our limbs in space as a vector.

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Section: Discussionmentioning

confidence: 99%

Vector coding in slow goal-directed arm movements

Graaf

Gon

Sittig

1996

Perception & Psychophysics

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“…Because of its excellent agreement with these experimental observations, the minimum-jerk principle became one of the most influential motor control theories. In several publications, Flash (1990), Hogan (1988), and Hogan and Flash (1987) further popularized the minimum-jerk theory, and a number of researchers have since expanded its scope in various directions.…”

Section: Cartesian-space Planningmentioning

confidence: 99%

Minimum Principles in Motor Control

Engelbrecht¹

2001

Journal of Mathematical Psychology

140

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“…One possibility is that the nervous system varies movement time by varying the timing of muscle commands, based, for example, on an internal model of limb inertia. Alternatively, the direction-dependent variations in movement time in control subjects might emerge as a consequence of the interactions of limb inertia and joint stiffness associated with changes in equilibrium position (Bizzi et al 1984;Flash 1990;Hogan 1988). One version of this idea, Feldman's lambda model, proposes that the regulation of joint stiffness depends on proprioceptive feedback.…”

Section: Compensation For Direction-dependent Variations In Limb Inertiamentioning

confidence: 99%

Impairments of reaching movements in patients without proprioception. II. Effects of visual information on accuracy

Ghez

Gordon²,

Ghilardi³

1995

Journal of Neurophysiology

324

170

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SUMMARY AND CONCLUSIONSVictor 198 1) . This degradation when vision is absent gener-I. The aim of this study was to determine how vision of a cursor indicating hand position on a computer screen or vision of the limb itself improves the accuracy of reaching movements in patients deprived of limb proprioception due to large-fiber sensory neuropathy. In particular, we wished to ascertain the contribution of such information to improved planning rather than to feedback corrections. We analyzed spatial errors and hand trajectories of reaching movements made by subjects moving a hand-held cursor on a digitizing tablet while viewing targets displayed on a computer screen. The errors made when movements were performed without vision of their arm or of a screen cursor were compared with errors made when this information was available concurrently or prior to movement.2. Both monitoring the screen cursor and seeing their limb in peripheral vision during movement improved the accuracy of the patients' movements. Improvements produced by seeing the cursor during movement are attributable simply to feedback corrections. However, because the target was not present in the actual workspace, improvements associated with vision of the limb must involve more complex corrective mechanisms.3. Significant improvements in performance also occurred in trials without vision that were performed after viewing the limb at rest or during movements. In particular, prior vision of the limb in motion improved the ability of patients to vary the duration of movements in different directions so as to compensate for the inertial anisotropy of the limb. In addition, there were significant reductions in directional errors, path curvature, and late secondary movements. Comparable improvements in extent, direction, and curvature were produced when subjects could see the screen cursor during alternate movements to targets in different directions.4. The effects of viewing the limb were transient and decayed during a period of minutes once vision of the limb was no longer available.5. It is proposed that the improvements in performance produced after vision of the limb were mediated by the visual updating of internal models of the limb. Vision of the limb at rest may provide configuration information while vision of the limb in motion provides additional dynamic information. Vision of the cursor and the resulting ability to correct ongoing movements, however, is considered primarily to provide information about the dynamic properties of the limb and its response to neural commands.

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Planning and execution of multijoint movements

Cited by 105 publications

References 18 publications

Vector coding in slow goal-directed arm movements

Vector coding in slow goal-directed arm movements

Minimum Principles in Motor Control

Impairments of reaching movements in patients without proprioception. II. Effects of visual information on accuracy

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