Update on neuroimaging findings in autism spectrum disorder

Purpose - Autism spectrum disorder (ASD) has been studied as a neurodevelopmental disorder since Leo Kanner's early observations of abnormal head circumference in autistic children. In the past few years, there has been much progress made in elucidating the anatomical and functional abnormalities in ASD. This paper aims to summarise the extant research. Design/methodology/approach - This paper provides a summary of relevant research findings in the neuroimaging of autism for the past 12 month period. Papers were identified using the Medline search terms: autism; ASD (functional); magnetic resonance imaging (MRI); neuroimaging; diffusion tensor imaging (DTI); and endophenotype. Findings - Relatively recent techniques such as functional MRI and DTI have furthered the initial work derived from early histological and structural imaging studies. Even newer techniques, such as DTI tractography and support vector machine analysis, and other computer- based learning methods have allowed us to move beyond regional variations in grey and white matter volume and study ASD as a disorder of connectivity, and of regional cerebral function and neural circuitry. Brain regions and neural circuits that are implicated in the core symptoms of ASD (deficits in social reciprocity, language and communication, and restricted and stereotyped interests) have been repeatedly shown to be abnormal in those individuals. Originality/value - This paper aims to provide a background for clinicians to the current research and focuses on developments in the field of neuroimaging of ASD from the past year, which have generated further insights into the neurobiology of ASD.