Sequential aiming movements and the one-target advantage in individuals with Down syndrome

Abstract

Research has revealed that individuals with Down syndrome (DS) have elevated reaction times, longer movement times, and greater movement errors during single-target single-limb actions compared to their typically developing (TD) peers. These perceptualmotor impairments have been attributed to both central processes and the physical phenotype associated with DS. The purpose of the present study was to directly investigate these possible central and peripheral deficits by examining how individuals with DS plan and execute more complex movements. Three groups (DS, TD, and individuals with an undifferentiated intellectual disability; UID) of 8 participants completed a single target movement, a two-target movement performed by a single arm, and a two-target movement where the first movement was performed with one arm and the second movement performed with the other arm. For all groups and all conditions, movement times revealed a one-target advantage (OTA). Specifically, times to the first target were longer in the two-target responses compared to the single-target response. In general, the OTA finding reveals that persons with DS utilise planning strategies similar to their TD peers when performing sequential actions involving two targets and two arms. Furthermore, because the OTA was observed in both the single-and two-arm two-target responses the interference in movement one associated with having to make a subsequent movement is not due to peripheral processes associated with single limb constraints. Rather, individuals with DS treat movements within a sequence as functionally dependent. Thus, the central processes associated with the timing of the implementation of the second element of the movement appear to be responsible for the interference that leads to the OTA. MOVEMENT INTEGRATION IN PERSONS WITH DOWN SYNDROME3

The multiple process model of goal-directed aiming/reaching: insights on limb control from various special populations

“…Children and adults with Down syndrome take more time to initiate and complete goal-directed aiming movements than their chronological age counter-parts from the general population (Chen et al 2015;Elliott et al 2006;Gimenez et al 2017;Hodges et al 1995;Lawrence et al 2013;Vimercati et al 2012). This perceptual-motor slowness is particularly evident when the accuracy demands of the movement are high (Hocking et al 2011;Lam et al 2009).…”

“…This perceptual-motor slowness is particularly evident when the accuracy demands of the movement are high (Hocking et al 2011;Lam et al 2009). As well, adults with Down syndrome take more time between movement components, than do adults without Down syndrome, when performing reciprocal aiming movements (Lam et al 2009) and multi-component aiming movements involving reversals (Reilley et al 2017), but not when performing sequential movements with only two components (Lawrence et al 2013).…”

Motor Coordination and Global Development in Subjects with Down Syndrome: The Influence of Physical Activity

“…Nevertheless, motor impairments in the DS population refer to restrictions in domains such as motor planning and control, locomotion and object control skill, manual dexterity, fine motor skills, and writing skills [ 19 , 20 , 21 , 22 ]. In both children and adults with DS, impaired movement fluency and axial control, hypotonia, and disorders in coordination and body balance, that negatively affect gross motor skills, can be attributed to the decreased size of the corpus callosum and cerebellum, reduced superior temporal gyrus and reduced volume of the brainstem [ 7 , 10 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ].…”

A note on motor skill acquisition in mild and moderate Down syndrome individuals

“…The adaptive control strategy used by DS individuals was also highlighted by the greater number of movement unities given by the velocity profile of the wrist which means greater reliance on feedback control. Lawrence et al (2013) conducted a study bringing evidence that central factors rather peripheral ones play a major role in the deficits observed in the motor performance of individuals with Down syndrome. They specifically tested the one-target advantage hypothesis (OTA) in sequential aim movements.…”

“…It will be longer when there is more than one target. Lawrence et al (2013) asked DS individuals to perform a single target movement, a two-target movement performed by a single arm, and a two-target movement performed bi-manually (the first movement was performed with one arm, and the second movement with the other arm). OTA was observed for DS individuals in a similar strategy observed with the other participants in the study (typically developing individuals and individuals with an undifferentiated intellectual disability).…”