Movement Preparation in High-Functioning Autism and Asperger Disorder: A Serial Choice Reaction Time Task Involving Motor Reprogramming

Autism and Asperger disorder have long been associated with movement abnormalities, although the neurobehavioural details of these abnormalities remain poorly defined. Clumsiness has traditionally been associated with Asperger disorder but not autism, although this is controversial. Others have suggested that both groups demonstrate a similar global motor delay. In this study we aimed to determine whether movement preparation or movement execution was atypical in these disorders and to describe any differences between autism and Asperger disorder. A simple motor reprogramming task was employed. The results indicated that individuals with autism and Asperger disorder have atypical movement preparation with an intact ability to execute movement. An atypical deficit in motor preparation was found in Asperger disorder, whereas movement preparation was characterised by a “lack of anticipation” in autism. The differences in movement preparation profiles in these disorders were suggested to reflect differential involvement of the fronto-striatal region, in particular the supplementary motor area and anterior cingulate.

Discussion
The results from this study show that individuals with autism and Asperger disorder have a normal ability to execute movements in this motor reprogramming paradigm. Of particular interest, however, was the finding that both the HFA and AD groups showed anomalies in movement preparation. These findings are generally comparable with those of Hughes who showed that autism is associated with an atypical planning and anticipation of a motor response. Also of interest was the finding that movement was prepared for differently by the HFA and AD groups. The movement preparation displayed by the autism group appeared to be lacking in a normal anticipatory pattern.