Search PubMed⌕ Search

Biomedical subjects

A M Wing

Publications and source records attributed to A M Wing.

48 records · Page 3Linked to original sources
PubMed1988

Relation between velocity and curvature in movement: equivalence and divergence between a power law and a minimum-jerk model.

Unconstrained hand movements typically display a decrease in hand speed around highly curved sections of a trajectory. It has been suggested that this relation between tangential velocity and radius of curvature conforms to a one-third power law. We demonstrate that a one-third power law can be explained by models taking account of trajectory costs such as a minimum-jerk model. Data were analyzed from 6 subjects performing elliptical drawing movements of varying eccentricities. Conformity to the one-third power law in the average was obtained but is shown to be artifactual. It is demonstrated that asymmetric velocity profiles may result in consistent departures from a one-third power law but that such differences may be masked by inappropriate analysis procedures. We introduce a modification to the original minimum-jerk model by replacing the assumption of a Newtonian point-mass with a visco-elastic body. Simulations with the modified model identify a basis for asymmetry of velocity profiles and thereby predict departures from a one-third law commensurate with the empirical findings.

Adult↗
PubMed1986

Grasp size and accuracy of approach in reaching.

In reaching for an object in the environment, it has been suggested that movement components concerned with transport of the hand toward the object and those related to grasping the object are organized and executed independently. An experiment is reported that demonstrates people adjust grasp aperture to compensate for factors affecting transport error. Grasp aperture was found to be greater in reaching movements performed faster than normal, and grasp aperture was also found to be wider when reaching with the eyes closed. In both cases, transport was spatially less accurate. It is argued that, in advance of movement, formation of grasp is planned to take into account not only the perceived characteristics of the object but, also, internalized information based on past experience about the likely accuracy of the transport component.

Journal Article↗
PubMed1984

Basal ganglia lesions and psychological analyses of the control of voluntary movement.

Psychological accounts of the voluntary control of movement recognize the contribution of perceptual and decision processes as well as processes such as motor memory and timing that are more obviously a part of motor control. A model including these and other components is outlined in relation to tracking, a task that has often been used to study human perceptual-motor performance. The need for experimental control in addressing such multi-process models is emphasized. A number of studies of perceptual-motor performance deficits in patients with Parkinson's disease are reviewed. The methods by which the studies relate the behavioural data to the hypothesized underlying processes may be broadly grouped according to whether they use a subtractive logic or take a decompositional approach. These studies suggest that the basal ganglia play a role in the activation of pre-planned movement.

Basal Ganglia Diseases↗
PubMed1984

Motor disorder and the timing of repetitive movements.

This paper is concerned with the timing of regular repetitive movements. The two-process model of Wing and Kristofferson attributes variability in self-paced interresponse intervals to imprecision in a timekeeper and to temporal noise in the execution of motor responses triggered by the timekeeper. Assuming independence of timekeeper intervals and motor delays, the variance of each may be estimated from interresponse-interval statistics. Comparison of changes in timing performance associated with alterations in motor-system functioning offer the possibility of a new approach to investigation of this model. Illustrative data are presented from a case study of a patient with Parkinson's disease whose lesions affecting the dopaminergic pathways of the basal ganglia have given rise to asymmetric symptoms, including differences in timing performance of the two hands. Analysis of interresponse-interval variability according to the two-process model indicates that the elevated variability of the side more greatly affected by parkinsonism is attributable to the timekeeper intervals rather than the motor delays.

Adult↗
PubMed1980

Timing of movement phases of a repeated response.

How can one determine the nature of timing control that exists among various distinct phases of movement in a repetitive activity? A statistical approach is suggested and is exemplified by reference to data on the timing of two phases of movement, arrival at and departure from the response plate, in repetitive finger tapping. Two contrasting models are presented, and the predictions for the covariation of the various intervals between the two movement phases are compared. Data on finger tapping support the model that assumes the initiation of each phase is centrally determined without reference to the time of occurrence of the immediately preceding phase.

Journal Article↗
PubMed1978

Effects of sleep deprivation on short duration performance measures compared to the Wilkinson auditory vigilance task.

The effects of one night's total sleep deprivation were examined using the Wilkinson vigilance task and four 10 min duration performance tests. A repeated measures design was used in which eight male subjects experienced one night of sleep loss, the order of sleep loss being balanced across subjects. The four short duration performance tests consisted of choice reaction time, simple reaction time, short-term memory, and a motor task, handwriting. The results confirm the effects of one night's sleep deprivation on the vigilance task and also show that performance on the two reaction time tests was significantly impaired by the loss of sleep, but not at such a high level as for the vigilance. The short-term memory test failed to show any adverse effects of sleep loss and similarly for the handwriting. The experiment shows that two portable and brief (10 min) performance tests are sensitive indices of sleep loss and should be particularly useful for assessing levels of alertness in the field.

Adult↗
PubMed1977

Pharmacokinetics and concentration-effect relationships of intervenous and oral clonidine.

The kinetics of the disposition of intravenous and oral clonidine in five normotensive subjects have been determined. It is proposed that a two-compartment model adequately describes the disposition of the drug. The drug is rapidly distributed (t1/2alpha = 10.8 +/- 4.7 min) but slowly elimainated (t1/2beta = 8.5 +/- 0.9 hr). The bioavailability of oral clonidine in the tablets tested averaged 75.2% and 40 to 50% of the bioavailable dose is excreted unchanged in urine. Renal clearance of the drug showed considerable intersubject variation (1.82 +/- 0.34 ml/min/kg) and exceed the calculated glomerular filtration rate in some subjects. Oral and intravenous clonidine induced significant falls in blood pressure (greater than 20/15 mm Hg) in our normotensive subjects and consistently caused marked sedation and dryness of the mouth. Sedation and salivary flow correlated with plasma clonidine concentration over the range 0 to 4 ng/ml. Falls in blood pressure were related to plasma concentration to 1.5 to 2 ng/ml but at higher concentrations the hypotensive effect was attenuated.

Administration, Oral↗
PubMed1977

Perturbations of auditory feedback delay and the timing of movement.

Among theories concerned with the timing of movement sequences, an important distinction exists between those that assume closed-loop control (in which feedback contingent on one response starts the chain of events that leads to the next response) and those that assume open-loop control (in which feedback does not serve that function). An experiment is reported in which subjects had to make repetitive finger-tapping responses at fixed intervals of 350, 500, or 650 msec. A brief auditory signal was fed back to the subject after each response, and once in each trial, the auditory feedback delay associated with one response selected at random was perturbed by a small amount. It was found that such perturbations affected the immediately subsequent interresponse interval, which is evidence against the simple open-loop model. However, the effects, although in the same direction as the perturbation, were smaller in magnitude, a finding that rejects the simple closed-loop model. In discussing these results it is suggested that subjects operated chiefly in open-loop fashion but monitored the auditory feedback, making compensatory attempts when intervals between auditory feedback events grossly deviated from the desired interresponse interval.

Auditory Perception↗