Neuropsychological investigation of motor impairments in autism

Abstract

It is unclear how standardized neuropsychological measures of motor function relate to brain volumes of motor regions in autism spectrum disorder (ASD). An all-male sample composed of 59 ASD and 30 controls (ages 5–33 years) completed three measures of motor function: strength of grip (SOG), finger tapping test (FTT), and grooved pegboard test (GPT). Likewise, all participants underwent magnetic resonance imaging with region of interest (ROI) volumes obtained to include the following regions: motor cortex (precentral gyrus), somatosensory cortex (postcentral gyrus), thalamus, basal ganglia, cerebellum, and caudal middle frontal gyrus. These traditional neuropsychological measures of motor function are assumed to differ in motor complexity, with GPT requiring the most followed by FTT and SOG. Performance by ASD participants on the GPT and FTT differed significantly from that of controls, with the largest effect size differences observed on the more complex GPT task. Differences on the SOG task between the two groups were nonsignificant. Since more complex motor tasks tap more complex networks, poorer GPT performance by those with ASD may reflect less efficient motor networks. There was no gross pathology observed in classic motor areas of the brain in ASD, as ROI volumes did not differ, but FTT was negatively related to motor cortex volume in ASD. The results suggest a hierarchical motor disruption in ASD, with difficulties evident only in more complex tasks as well as a potential anomalous size–function relation in motor cortex in ASD.

Keywords:

• Autism
• Network disruption
• Motor impairment
• Brain volume differences
• Motor cortex volume

The project described was supported by Grants RO1 MH080826 (J.E.L., E.D.B., A.L.A., N.L.), RO1 MH084795 (J.E.L., P.T.F., N.L.), and KO8 MH092697 (J.S.A.) from the National Institute of Mental Health; Grants T32 HD07489 (B.T.) and P30 HD003352-45 (Waisman Center Core Grant) from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), The Hartwell Foundation (B.T.), and the Primary Children’s Foundation Early Career Development Award (B.Z.). Support from the Poelman Foundation to Brigham Young University for autism research is gratefully acknowledged. The authors report no conflicts of interest. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Mental Health, the National Institute of Child Health and Development, or the National Institutes of Health. We thank former members of the Utah Autism Creative Programs of Excellence in Autism (CPEA) for their assistance during the early stages of this project. We sincerely thank the children, adolescents, and adults with autism and the individuals with typical development who participated in this study and their families. The assistance of Tracy J. Abildskov with image analysis and Jo Ann Petrie with manuscript preparation is gratefully acknowledged.