Executive Dysfunction in Autism Spectrum Disorders; are siblings affected?

Background: People with high functioning autism (HFA) have difficulties in social interaction, communication and behaviour, but normal intelligence. In HFA, deficits in the executive function of response-inhibition (eg. inability to suppress context-inappropriate behaviour) lead to conduct that is unsuitable and socially embarrassing^{[Kana et al, 2007]}. Recent research from our laboratory suggests a specific deficit in response-inhibition in children with HFA using the Sustained Attention to Response Task (SART)^{[Johnson et al, 2007]}. Executive dysfunction (held to account for the defining behavioural features of autism^{[Turner, 1999]}) has been reported both in probands with HFA and their close relatives, suggesting that executive function may play a central role in the aetiology of autism^{[Wong et al, 2006]}. However, there are a very limited number of studies investigating executive function in relatives of individuals with HFA. This is surprising as this strategy is important in determining which cognitive deficits are potential endophenotypes for autism ^{[Hughes et al, 1999]}. We hypothesise that there will be response-inhibition deficits in probands with ASD and partial deficits in their unaffected siblings suggesting that this executive function is familial and heritable and may be a useful cognitive endophenotype for use in future studies attempting to localise susceptibility genes for autism.

Objectives:

1. To characterise the performance of children with and without HFA on a task testing response inhibition.
   

2. To determine the familiality/heritability of response-inhibition, by comparing the performance of children with HFA, their unaffected siblings, and control participants on a task of response inhibition.
   

Methods:

Neuropsychological testing will be carried out in HFA probands, unaffected siblings, and controls using the SART to assess response-inhibition, and Wechsler Intelligence Scale for Children (WISC-IV) to assess IQ. Neuropsychological data will be analysed using ANOVA and regression analyses.

Results:

Data is currently being collected. Results will be discussed in relation to current theory.

Conclusions:

To be discussed.