Abnormalities in glutamate/glutamine may partially underpin the pathophysiology of autistic spectrum disorders, and the authors confirm earlier reports that limbic areas are metabolically aberrant in these disorders.

There is some consensus in the literature regarding the cognitive profile of people with Asperger syndrome (AS). Findings to date suggest that a proportion of people with AS have higher verbal than performance IQ, a non-verbal learning disability (NVLD) and impairments in some aspects of executive function (EF). However, there are few published studies on adults with AS and many have compared the AS group to an autistic control group alone. We compared cognitive functioning in 27 AS adults without a history of language delay and 20 normal controls who did not differ significantly in age, gender and IQ. People with AS had significant impairments on a test of visual memory and on EF tasks measuring flexibility and generativity, but not inhibition. There was no significant difference between verbal and performance IQ. Our results suggest that impairments on tests requiring flexibility of thought and generation occur at all ages and across a range of autistic disorders including AS.

Although 22q11DS children have specific cognitive deficits, differences in COMT do not account for these findings.

Executive functioning deficits characterize the neuropsychological profiles of the childhood neurodevelopmental disorders of attention deficit hyperactivity disorder (ADHD) and autistic spectrum disorder (ASD). This study sought to determine whether similar impairments exist in adults with ADHD (N = 53) and ASD (N = 45) in comparison with a healthy control group (N = 31), whether the two disorders can be distinguished on the basis of their executive functioning features, and whether these impairments are related to symptom severity. Both clinical groups were found to exhibit executive functioning deficits. The ADHD group had difficulty withholding a response, with relative preservation of initiation and planning abilities. In contrast, the ASD group exhibited significant impairments in initiation, planning and strategy formation. The specific executive functioning deficits were related to severity of response inhibition impairments in ADHD and stereotyped, repetitive behaviours in ASD. These findings suggest the pattern of executive functioning deficits follows a consistent trajectory into adulthood.

22q11.2 deletion syndrome (22q11DS) is a genetic disorder associated with a microdeletion of chromosome 22q11. In addition to high rates of neuropsychiatric disorders such as schizophrenia and attention deficit hyperactivity disorder, children with 22q11DS have a specific neuropsychological profile with particular deficits in visuospatial and working memory. However, the neurobiological substrate underlying these deficits is poorly understood. We investigated brain function during a visuospatial working memory (SWM) task in eight children with 22q11DS and 13 healthy controls, using fMRI. Both groups showed task-related activation in dorsolateral prefrontal cortex (DLPFC) and bilateral parietal association cortices. Controls activated parietal and occipital regions significantly more than those with 22q11DS but there was no significant between-group difference in DLPFC. In addition, while controls had a significant age-related increase in the activation of posterior brain regions and an age-related decrease in anterior regions, the 22q11DS children showed the opposite pattern. Genetically determined differences in the development of specific brain systems may underpin the cognitive deficits in 22q11DS, and may contribute to the later development of neuropsychiatric disorders.