Avril V. Brereton

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 characterized 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.

A Deficit in Shifting Attention Present in High-Functioning Autism but not Asperger’s Disorder:

The aim of this study was to examine executive functioning, in particular, attentional set-shifting deficits in high-functioning autism (n = 12) and Asperger’s disorder (n = 12). A large or global digit composed of smaller or local digits was presented during each trial. The participants indicated the presence of 1s or 2s by pressing the appropriate button. These targets could appear globally or locally. Relative to IQ, sex and age matched controls, reaction time to global targets in individuals with autism was retarded when the previous target appeared locally. This deficiency in shifting from local to global processing, however, was not observed in individuals with Asperger’s disorder. The theoretical and neurobiological significance of this dissociation in executive functioning in these clinically related disorders was explored.

Lateralization in individuals with high-functioning autism and Asperger's disorder: a frontostriatal model.

Neurobiological and behavioural studies of possible left hemisphere dysfunction in autism have generated conflicting results. Left hemisphere dysfunction may manifest in autism only in tasks that invoke executive functions. Moreover, left hemisphere dysfunction may underpin autism but not Aspergers disorder. We thus aimed to systematically investigate reports of anomalous lateralization in individuals with high-functioning autism and Aspergers disorder. Two of the tasks were sensitive to executive dysfunction: a serial choice reaction-time task and a Posner-type paradigm; the remaining tasks instead investigated aspects of perceptual lateralisation. Compared with age- and IQ-matched controls, the autism group displayed deficiencies in right hemispace (and by implication, left hemisphere) performance on both executive function tasks; however, this group demonstrated normal lateralization effects on the nonexecutive, visual-perceptual tasks. In contrast, the Aspergers disorder group showed similar laterality effects to their age- and IQ-matched controls on both executive and nonexecutive function tasks. The etiological relevance of this neurobehavioral dissociation between high-functioning autism and Aspergers disorder was discussed; in particular, it was suggested that the period where dominance shifts from right to left hemisphere is important in whatever process might dictate the emergence of either autism or Aspergers disorder.

Screening for Autism in Infants, Children, and Adolescents

Publisher Summary Screening of at risk children who have developmental problems might more effectively channel referrals to the scarce resource at specialist assessment services for autism and improve the rate of early diagnosis. This chapter reviews the reliability, validity, and utility of the currently available instruments designed to screen for autism. Primary care professionals, such as general practitioners, community pediatricians, and child health nurses, are usually in the best position to implement screening procedures, but they have limited time and may not have trained in the identification of complex childhood disorders. It is, therefore, essential that screening be neither time consuming nor requires extensive training. Ideally, a screening tool should be brief, be able to be completed by parents, and enable easy identification of those children requiring referral for specialist assessment. Screening instruments specifically developed for autism include measures for use with infants and preschool children and those for use with older young people. These two groups are considered separately in this chapter.