Biomedical subjects

Laurette Hay

Publications and source records attributed to Laurette Hay.

7 recordsLinked to original sources

PubMed2006

Age-related differences in the reaching and grasping coordination in children: unimanual and bimanual tasks.

This study examined age-related differences in the coordinative mechanism of the reach-to-grasp movement in three groups of children aged 6, 8, and 11 year, and in healthy adults. Three prehension conditions were manipulated: an unimanual and a bimanual self-driven tasks in which the reaching and grasping of the object were performed by participants, and a bimanual externally-driven task, in which the experimenter brought the object into the vicinity of the participant which grasped it. Classical kinematics data-peak velocities of the reaching and the grasping, the time to onset grip opening, maximum grip opening and grip closure-were calculated. Moreover, to obtain equivalent kinematics variables for all age groups, relative time to peak velocity (% of reaching duration), relative maximum grip opening (% of object size), and percentage of the four types of phase plans between reaching velocity and grip size have been calculated for each group of age. Our main results showed (1) a high variability at age 6, (2) an age-related change between the 6- and 8-year old for almost all of the dependent variables, and (3) a significant difference between the 11-year olds and adults. In summary, at 6 years, the interdependence between the reaching and grasping programs was unstable. A transitory feedback-based coordination between reaching and grasping appeared at 8 years of age. Finally, the adults' relationship between reaching and grasping was not attained at the age of 11.

Adult↗

PubMed2006

Response delay and spatial representation in pointing movements.

Pointing movements decrease in accuracy when target information is removed before movement onset. This time effect was analyzed in relation with the spatial representation of the target location, which can be egocentric (i.e. in relation to the body) or exocentric (i.e. in relation to the external world) depending on the visual environment of the target. The accuracy of pointing movements performed without visual feedback was measured in two delay conditions: 0 and 5-s delay between target removal and movement onset. In each delay condition, targets were presented either in the darkness (egocentric localization) or within a structured visual background (exocentric localization). The results show that pointing was more accurate when targets were presented within a visual background than in the darkness. The time-related decrease in accuracy was observed in the darkness condition, whereas no delay effect was found in the presence of a visual background. Therefore, contextual factors applied to a simple pointing action might induce different spatial representations: a short-lived sensorimotor egocentric representation used in immediate action control, or a long-lived perceptual exocentric representation which drives perception and delayed action.

Adult↗

PubMed2005

Role of visual context and oculomotor conditions in pointing accuracy.

Localizing a target in the extrapersonal space may rely on two types of spatial coordinate systems: egocentric or exocentric. Two experiments investigated the role of these systems in the accuracy of goal-directed movements. The accuracy of pointing movements performed without visual feedback of the hand was measured in two conditions of target presentation (darkness or within a visually structured background), and in two conditions of eye-hand coordination (eye fixed on a fixation point, or with a foveation saccade). The results showed (1) that pointing accuracy increased in the presence of a visual background, and (2) enhancement of this beneficial effect by a steady retinal image of target and background, that is without a foveation saccade. An object that has to be reached in the prehension space can be localized in two ways: (1) in relation to the body (egocentric), induced by the absence of a structured visual environment, (2) in relation to the external space (exocentric), favored by the presence of a visually structured background. We investigated the importance of the localizing mode in the accuracy of reaching movements, and how the two modes can be optimized. We found better reaching accuracy with exocentric than with egocentric localization, particularly when the retinal image of the goal and its environment was stabilized in the absence of eye movements.

Eye Movements↗

PubMed2005

Role of proprioceptive information in movement programming and control in 5 to 11-year old children.

The role of proprioceptive inputs in the control of goal-directed movements was examined, by means of the tendon vibration technique, in 5 to 11-year old children performing a serial pointing task. Children pointed, with movements of various amplitudes and at various positions, by alternating wrist flexions and extensions. Tendon vibration was applied to both agonist and antagonist muscles to perturb relevant muscular proprioceptive inputs during the static or dynamic phase of the task, i.e., during stops on targets or during movement execution. Constant and variable amplitude errors as well as constant position error were evaluated. Vibratory perturbation applied during movement execution resulted in a similar reduction in movement amplitude, yielding an increased constant error in all age groups and a systematic position error in the direction of the movement starting point. Perturbing proprioception during static phases preceding movement resulted in an age-related increase in the variable amplitude error, which was maximal in 5-year old children performing extension movements. The results were interpreted in terms of the use of proprioceptive information in the feedforward and feedback based components of movement control in children. In particular, the results indicated (1) developmental changes in the relative weighting of each component, (2) an increased capacity to move from one strategy to the other, depending on the availability of information, and (3) developmental changes from an alternated to an integrated control of amplitude and position in serial pointing.

Biomechanical Phenomena↗

PubMed2003

Interhemispheric relationships in 4- to 14-year-old children pointing to lateral targets.

Some developmental changes in movement control are not monotonic during childhood, which leads us to question how hemispheric relationships develop since they are closely involved with visuo-manual coordination. We tested right-handed children between 4 and 14 years of age performing pointing movements with the right and left hand towards visual targets located in the right and left hemifield. The analysis of movement parameters showed a left hand advantage in reaction time, but this is mainly due to the contralateral movements relative to the semifield of target presentation, suggesting that hemispheric asymmetry is not achieved even in older children. Interhemispheric transfer was evaluated through the difference between crossed (opposite hand and hemifield side) and uncrossed (same hand and hemifield side) movements. The difference was significant at all ages, and decreased with age between 4-6 and 7-9 years. It moved from early asymmetry in favor of the left-to-right interhemispheric transfer to adult-like symmetry at 10-14 years. The long development of hemispheric specificity and interhemispheric communication suggested by our results might be associated to asynchronous development of various processes involved in visuo-motor coordination, leading to qualitative changes in visually directed movement during childhood described in the literature.

Adolescent↗

PubMed2003

Information processing and movement optimization during development: kinematics of cyclical pointing in 5- to 11-year-old children.

The authors studied the development of movement control in speed-accuracy tradeoff conditions in children aged 5-11 years and in adults performing cyclical pointings. Twelve difficulty levels (IDs), ranging from 2 to 6.58 bits, were defined (P. M. Fitts, 1954). Peak and time to peak velocity, acceleration, and deceleration, and acceleration profiles as a function of hand position (Hooke's portraits) were analyzed. Movement time decreased with age and was less affected by ID. Peak velocity and acceleration increased, acceleration and deceleration were decreasingly time consuming, and movement profiles turned to increased harmonicity with age and task easiness. Nevertheless, the developmental trends differed between parameters. Gain in velocity seemed chiefly dependent on improved muscular cooperation patterns before 7 years of age and on improved information processing from age 7 onward; achievement of an optimized strategy in the speed-accuracy tradeoff occurred at age 11 years.

Acceleration↗

PubMed2002

Visuomanual coordination in childhood: adaptation to visual distortion.

The aim of the experiment was to study the adaptive capacities of children to perform drawing movements while being visually perturbed. Children aged 5-11 years and a group of adults drew diamonds via information provided through a computer screen. The screen display was either upright or rotated 180 degrees. Results showed that the absence of direct vision of the hand yielded more perturbation in the youngest group of children compared to all other groups. In spite of some initial difficulty, all children reached accurate control after five trials. When faced with spatial rotations of the visual field, youngsters were again more perturbed than others. All children showed the same rate of adaptation to visual rotations, but they differed on adaptive strategies. Five- and 7-year-olds shifted to a feedforward mode of control consisting of the production of a rapid gesture, followed by error evaluation in order to correct their next movement. Older children were characterised by a progressive integration of reafferent visual and proprioceptive information. It resulted in an increase in duration of strokes and reduced speed, meaning enhanced on-line retrieval of information. However, 9-year-old children experienced more difficulty recuperating sensory information during movement than 11-year-olds, and kept using error feedback. Finally, visuomanual coordination in children aged 11 years, while slightly differing from that of adults, was not yet totally mature.

Adaptation, Physiological↗