Visual Information and the Control of Reaching in Children: A Comparison Between Children With and Without Developmental Coordination Disorder

Abstract

Three experiments were performed on reach and grasp in 9- to 10-year-old children (8 controls and 8 with developmental coordination disorder [DCD]). In normal reaching, children in the DCD group were less responsive to the accuracy demands of the task in controlling the transport component of prehension and spent less time in the deceleration phase of hand transport. When vision was removed as movement began, children in the control group spent more time decelerating and reached peak aperture earlier. Children in the DCD group did not do that, although, like the control group, they did increase grip aperture in the dark. When depth cues were reduced and only the target or only the target and hand were visible, children in the control group used target information to maintain the same grip aperture in all conditions, but DCD children behaved as if the target was not visible. Throughout the studies, the control group of 9- to 10-year-olds did not produce adult-like adaptations to reduced vision, suggesting that they had not yet attained adult-like integration of sensory input. Compared with control children, children with DCD did not exhibit increased dependence on vision but showed less recognition of accuracy demands, less adaptation to the removal of vision, and less use of minimal visual information when it was available.

Visual Feedback and Target Size Effects on Reach-to-Grasp Tasks in Children with Autism

“…Especially, children with autism as well as controls showed longer MT, smaller PV, smaller PTPV, larger NJS, and smaller PTMGA in non-visual feedback and small target blocks. Thus, these findings were consistent with previous studies (Jakobson and Goodale 1991;Kuhtz-Buschbeck et al 1998a, b;Smyth et al 2001). Also, in the absence of visual information and higher task-accuracy, both groups needed longer executing time and longer correctional phrase.…”

“…Time to MGA is the time from movement onset to MGA, and its percentage in MT is PTMGA (Kuhtz-Buschbeck et al 1998b). Therefore, Smyth et al (2001) on this note, stated that when the degree of task difficulty is higher, PTMGA would be smaller, which means MGA occurs earlier.…”

A test of motor (not executive) planning in developmental coordination disorder and autism.

“…We found a clear developmental trend in line with this hypothesis where younger children (aged 5-8 years) showed a greater bias towards selecting an MR grip than older children (aged 9-14 years). We had also hypothesised that a group of children with DCD would be biased towards MR at all ages due to their known prehension difficulties (Smyth, Anderson & Churchill 2001;Mon-Williams et al, 2005). The children with DCD showed the predicted bias towards MR, and the proportion of children with DCD who showed the MR bias was higher than even the youngest group of typically developing children.…”

Development of Prehension Between 5 and 10 Years of Age: Distance Scaling, Grip Aperture, and Sight of the Hand

“…Smyth, Peacock, and Katamba (2004) found that 5-and 6-year-old children did not spend more time in the low-velocity phase of movement when they could not see their hand and did not increase grip aperture, as 9-and 10-year-olds did and as adults have been shown to do. In addition, in a study of reach and grasp in 9and 10-year-old children with poor coordination, Smyth, Anderson, and Churchill (2001) found that these children showed less asymmetry in velocity profiles when reaching in normal light and that they were less affected by the removal of sight of the hand and the target than were agematched control children. Younger children, and children with poor coordination, do not respond to absence of sight of the hand by slowing the end of the movement, thus increasing the asymmetry in the velocity profile, or by increasing error margins in grip aperture.…”