Abstract
Goal-directed hand movements are guided by sensory information and may be adjusted ‘online,’ during the movement. If the target of a movement unexpectedly changes position, trajectory corrections can be initiated in as little as 100 ms in adults. This rapid visual online control is impaired in children with developmental coordination disorder (DCD), and potentially in other neurodevelopmental conditions. We investigated the visual control of hand movements in children in a ‘center-out’ double-step reaching and grasping task, and examined how parameters of this visuomotor control co-vary with performance on standardized motor tests often used with typically and atypically developing children. Two groups of children aged 8–12 years were asked to reach and grasp an illuminated central ball on a vertically oriented board. On a proportion of trials, and at movement onset, the illumination switched unpredictably to one of four other balls in a center-out configuration (left, right, up, or down). When the target moved, all but one of the children were able to correct their movements before reaching the initial target, at least on some trials, but the latencies to initiate these corrections were longer than those typically reported in the adult literature, ranging from 211 to 581 ms. These later corrections may be due to less developed motor skills in children, or to the increased cognitive and biomechanical complexity of switching movements in four directions. In the first group (n = 187), reaching and grasping parameters significantly predicted standardized movement scores on the MABC-2, most strongly for the aiming and catching component. In the second group (n = 85), these same parameters did not significantly predict scores on the DCDQ′07 parent questionnaire. Our reaching and grasping task provides a sensitive and continuous measure of movement skill that predicts scores on standardized movement tasks used to screen for DCD.
Highlights
Almost from the moment able-bodied people wake up, they begin reaching and grasping for objects with their hands – bed covers, a cup of coffee, a toothbrush
The foregoing work on online control has compared groups of children with developmental coordination disorder (DCD) to typically developing (TD) children, but has not examined how children’s visual online control across a wide range of movement skills covaries with performance on the standardized tests of movement coordination. By testing children both with and without motor impairments, and by assessing a wide range of movement variables on a continuous scale, the present study explores which reaching and grasping parameters best predict scores on standardized measures of movement ability often used for assessing children with DCD – the Movement Assessment Battery for Children Second Edition (MABC-2; Henderson et al, 2007), and the Developmental Coordination Disorder Questionnaire (DCDQ 07; Wilson et al, 2000, 2009)
262 children completed the reaching and grasping task with sufficient valid trials (≥20, including at least one successful movement correction) for analysis
Summary
Almost from the moment able-bodied people wake up, they begin reaching and grasping for objects with their hands – bed covers, a cup of coffee, a toothbrush. Online Control Predicts MABC-2 Scores (Castiello et al, 1991; Paulignan et al, 1991a,b; Farnè et al, 2003; Tresilian, 2012) which is the ability to quickly and accurately correct one’s movement in response to unexpected changes in the hand or target’s position or orientation, for example, when grasping an object as it is falling from your desk (Ruddock et al, 2014) In such situations, the reaching movement must be altered online, to reduce the error and bring the hand and target closer together. Adjustments to the reaching component of prehension (i.e., hand position) based on changes in object position occur more rapidly than adjustments to the grasping component (hand orientation and grip aperture) based on changes in object size (Paulignan et al, 1991a,b)
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