Although brain structure in Autism Spectrum Disorders (ASD) has been extensively investigated using magnetic resonance imaging techniques, considerable heterogeneity across studies exists for findings at the level of individual brain structures and regions. An important theme to emerge, however, is of structural alterations within the neural circuit that has become known as the ‘social brain’ – including the amygdala, superior temporal sulcus, fusiform face area and orbito-frontal cortex. Evidence points also to altered structure in the caudate nucleus in association with restricted and repetitive behaviours. Diffusion tensor imaging studies suggest aberrant connectivity between social brain structures and also between these areas and other cortical regions. Important future roles for structural neuroimaging will include longitudinal studies to investigate developmental trajectories in ASD, and efforts to join together neuroimaging and genomic techniques and to relate these findings to neuropathological studies.

Background

The notion that mental illness is a somatic disorder of the brain was put forward in 1845 by Wilhelm Griesinger (Griesinger, 1845), first Professor of psychiatry and neurology in Berlin, and has been actively investigated ever since. The initial work was neuropathological as there existed no means of visualising the brain in life but clear cut results were obtained in some disorders (Alzheimer, 1897; Wernicke, 1881) and where no such findings could be demonstrated as in schizophrenia, work still continued (Dunlap, 1924; Klippel and Lhermitte, 1909).