Abstract
Autism Spectrum Disorders (ASDs) are a heterogeneous group of neurodevelopmental disorders that are diagnosed solely on the basis of behaviour. A large body of work has reported neuroanatomical differences between individuals with ASD and neurotypical controls. Despite the huge clinical and genetic heterogeneity that typifies autism, some of these anatomical features appear to be either present in most cases or so dramatically altered in some that their presence is now reasonably well replicated in a number of studies. One such finding is the tendency towards overgrowth of the frontal cortex during the early postnatal period. Although these reports have been focused primarily on the presumed pathological anatomy, they are providing us with important insights into normal brain anatomy and are stimulating new ideas and hypotheses about the normal trajectory of brain development and the function of specific anatomical brain structures. The use of model systems that include genetic model organisms such as the mouse and, more recently, human induced pluripotent stem cell‐derived brain organoids to model normal and pathological human cortical development, is proving particularly informative. Here we review some of the neuroanatomical alterations reported in autism, with a particular focus on well‐validated findings and recent advances in the field, and ask what these observations can tell us about normal and abnormal brain development.
Highlights
Autism Spectrum Disorders (ASDs) is characterised by persistent difficulties in communication and social interactions and restricted, repetitive patterns of behaviour, interests or activities
We will start by reviewing some of the most intriguing anatomical differences described between ASD and neurotypical brains and move on to discuss what these observations might teach us about how specific aspects of brain development are regulated to ensure normal anatomy and function
This study examined the brains of individuals between 1 and 50 years of age and, akin to previous studies, reported evidence of early frontal cortex overgrowth followed by a marked reduction in brain size in ASD cases (Courchesne et al 2011a)
Summary
ASD is characterised by persistent difficulties in communication and social interactions and restricted, repetitive patterns of behaviour, interests or activities. One of the most consistent neuroanatomical abnormalities observed in the postmortem analysis of brains from individuals with ASD is a substantial decrease in the size and number of Purkinje cells, primarily in the posterolateral neocerebellar and archicerebellar cortices (Fatemi et al 2012).
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