Motor control, motor planning and the development of hand preference and performance

Language lateralization is specific to the left-hemisphere in approximately 96.5% of the population, where the majority of right-handed individuals fall under this distinction. However, atypical cerebral lateralization may result in the absence of a distinct right-hand preference. Neural deficits characteristic of autism are stereotypically of left-hemisphere function, such as language skills; consequently, left-hemisphere dysfunction and non-right-handedness are well documented. In typical development, left-hemisphere specialization for motor planning has been noted, where preferred hand use is linked to an advantage in motor performance. In autism, motor impairments include an inability to plan, organize and coordinate movements; thus solidifying the link to left-hemisphere deficit. The purpose of this study was to explore motor control, motor planning and the development of hand preference and performance. Left-handed ( n = 18) and right-handed (n = 94) typically-developing children (3- to 12-year-olds; n = 92) and adults ( n = 20) participated. Furthermore, three right-handed children with Autism Spectrum Disorders (ASD; 5-, 7- and 11-year-old) were age-matched with typically-developing children for an observational analysis. The Waterloo Handedness Questionnaire, Annett Pegboard, WatHand Cabinet Test, Bimanual Coordination Beading Task, and Motor Planning Task were completed within two testing sessions separated by a minimum of 24 hours. Quantitative results with typically-developing participants highlight the importance of considering different elements when measuring handedness over repeated sessions, as preference, performance and observational measures each possess their own inherent strengths and weaknesses. That said, this study confirms use of the WatHand Cabinet Test as a reliable measure. Furthermore, this study offers support for a preferred-hand advantage for mobilizing and non-preferred use for stabilizing. Finally, extending the motor planning literature, this study suggests adult like patterns of beginning-state comfort emerge at age 7, where end-state comfort follows shortly after at age 9. Observational results comparing children with ASD to their typically-developing counterparts suggest motor deficits undoubtedly exist, where it can be suggested that motor planning deficits may separate children with Asperger's Syndrome from children with High Functioning Autism. Overall, this study highlights the importance for further research in children with ASD, as there may be implications for amendments to current diagnostic criteria and intervention protocol.