The present study aimed to provide preliminary insight into the integrity of motor imagery (MI) in adults with probable developmental coordination disorder (pDCD). Based on a strong body of evidence indicating that paediatric samples of DCD often experience difficulties engaging MI, we hypothesised that young adults with pDCD would demonstrate similar difficulties. The performance of 12 young adults (19–35 years) with pDCD was compared to 47 age-matched controls on a traditional mental hand rotation task. Mean inverse efficiency scores were generated for each participant by dividing each participant's mean RT by their proportion of correct responses at each of the stimuli presentation conditions. Preliminary analysis revealed that the performance profiles of individuals with pDCD and age-matched controls showed evidence of being constrained by the biomechanical and postural constraints of real movement, suggesting that both groups engaged in an embodied (MI) strategy to complete the task. Despite engaging in a MI strategy, however, young adults with pDCD were nonetheless significantly less efficient when doing so, shown by significant main effects for group on all group efficiency comparisons. Based on the assumption that MI provides insight into the internal ‘neural’ action representation that precedes action, we argue that the less efficient MI performance demonstrated by young adults with pDCD may indicate inefficiencies engaging or implementing internal action representations. Implications and directions for future research are discussed.
Developmental coordination disorder (DCD) is characterised by delayed motor development in the absence of an identifiable developmental or neurological impairment, and affects an estimated 5–6% of school-aged children (Zwicker, Harris, & Klassen, 2012a). Affected individuals present with a reduced capacity to learn and/or perform fundamental motor skills which interferes with their ability to complete a variety of tasks of everyday living including dressing themselves, eating with utensils, brushing their teeth, toileting, handwriting and playing sports and musical instruments (Zwicker et al., 2012a). Critically, the impact of DCD often extends beyond the motor domain with clumsy individuals presenting with higher rates of psychological (e.g. depression and anxiety), social (e.g. decreased quality of social relationships, isolation, social anxiety, social withdrawal), educational (e.g. decreased educational achievement) and health (e.g. increased risk of obesity and cardiovascular disease, Rivilis et al., 2011) problems in comparison to their typically developing peers (see Zwicker, Missiuna, Harris, & Boyd, 2012b for a good review). It was once thought that the poor motor skill typical of DCD was transitory and hence, these individuals were expected to grow-out of their motor impairment through the natural process of experiential learning and neuro-cognitive development. However, a burgeoning body of longitudinal and cross-sectional research beginning in the early 1990s has demonstrated that without targeted intervention the motor impairment characteristic of DCD often persists into adolescence and adulthood ( Cantell et al., 1994, Cantell et al., 2003, Losse et al., 1991 and Rasmussen and Gillberg, 2000). Critically, this also appears to be the case for the aforementioned associated health and psychosocial difficulties ( Kirby et al., 2011 and Kirby et al., 2013).
The present study showed that young adults with pDCD and age-matched controls were able to engage in a MI strategy to complete a traditional hand rotation task, as shown by efficiency performance profiles which in both cases obeyed the biomechanical and postural constraints of real movement. Importantly, however, the performance of adults with pDCD was significantly less efficient than that of age-matched controls. Based on the assumption that motor simulation provides insight into the integrity of internal action representations, we argue that this atypical performance profile shown by adults with pDCD may reflect inefficiencies generating and or manipulating internal representations of movement. The finding here that adults with pDCD show similar performance deficits to their younger counterparts on a task of MI is unique and provides valuable insight into our understanding of atypical motor skill across the developmental spectrum and the future development of targeted interventions for adults with atypical motor skill. To this end, future research investigating whether a MI training intervention similar that shown to be effective at improving motor skill in children with atypical motor skill is similarly effective at improving motor skill in adults with the disorder is warranted.
