Functional neuroimaging of set shifting in children with Autism Spectrum Disorder (ASD)

Background: Accumulating research on structural abnormalities strongly implicates the involvement of the frontal lobes in autism spectrum disorders (ASD). The current study will focus on differences in frontal activity in children with ASD as elicited by a set-shifting task, an executive function considered to be primarily mediated by the dorsolateral prefrontal cortex.

Objectives: To examine the neural activation in frontal cortex during a set-shifting task in a group of typically developing (TD) children and a group of children with ASD.

Methods: Participants are typically developing children and high-functioning children with ASD, between the ages of 7 and 12 years. Using colourful, child-friendly stimuli, the task requires participants to make a series of choices between bidimensional compound stimuli, based on a given rule. Periodically, the rule shifts; these shifts are either intradimensional or extradimensional. Neural activity is measured at the time of shift using functional Magnetic Resonance Imaging (fMRI). The ability to shift set/dimension is also measured behaviourally using the Cambridge Intradimensional Extradimensional Shift task, and general executive function using the Test of Everyday Attention for Children (TEAch).

Results: Based on results with a group of 13 young adults, it was hypothesized that the set-shifting task would elicit activation in the prefrontal cortex in the TD group, with intradimensional shifts activating more dorsolateral regions, a pattern that may become more focal with age; and these developmental trends would be abnormal or altered in the ASD group. It was also hypothesized that the pattern and extent of functional activity would be correlated with performance on behavioural measures of set shifting and executive function.

Conclusions: If differences are found in the pattern of neural activation in the children with ASD during the shifts, this lends weight to the theory that frontal dysfunction, and consequently executive dysfunction, may be contributing to symptoms of ASD.