Brain surface anatomy in adults with autism: the relationship between surface area, cortical thickness, and autistic symptoms.
Neuroimaging studies of brain anatomy in autism spectrum disorder (ASD) have mostly been based on measures of cortical volume (CV). However, CV is a product of 2 distinct parameters, cortical thickness (CT) and surface area (SA), that in turn have distinct genetic and developmental origins.
To investigate regional differences in CV, SA, and CT as well as their relationship in a large and well-characterized sample of men with ASD and matched controls.
Multicenter case-control design using quantitative magnetic resonance imaging.
Medical Research Council UK Autism Imaging Multicentre Study.
A total of 168 men, 84 diagnosed as having ASD and 84 controls who did not differ significantly in mean (SD) age (26  years vs 28  years, respectively) or full-scale IQ (110  vs 114 , respectively).
MAIN OUTCOME MEASURES
Between-group differences in CV, SA, and CT investigated using a spatially unbiased vertex-based approach; the degree of spatial overlap between the differences in CT and SA; and their relative contribution to differences in regional CV.
Individuals with ASD differed from controls in all 3 parameters. These mainly consisted of significantly increased CT within frontal lobe regions and reduced SA in the orbitofrontal cortex and posterior cingulum.
These differences in CT and SA were paralleled by commensurate differences in CV. The spatially distributed patterns for CT and SA were largely nonoverlapping and shared only about 3% of all significantly different locations on the cerebral surface.
Individuals with ASD have significant differences in CV, but these may be underpinned by (separable) variations in its 2 components, CT and SA.
This is of importance because both measures result from distinct developmental pathways that are likely modulated by different neurobiological mechanisms. This finding may provide novel targets for future studies into the etiology of the condition and a new way to fractionate the disorder.
Further Readings of Interest
Maternal autoantibodies are associated with abnormal brain enlargement in a subgroup of children with autism spectrum disorder.
Myeloid dendritic cells frequencies are increased in children with autism spectrum disorder and associated with amygdala volume and repetitive behaviors.
Neurogenesis, inflammation and behavior.
Brain enlargement and increased behavioral and cytokine reactivity in infant monkeys following acute prenatal endotoxemia.
Harlow Primate Laboratory, University of WisconsinAbstract
Infections and inflammatory conditions during pregnancy can dysregulate neural development and increase the risk for developing autism and schizophrenia. The following research utilized a nonhuman primate model to investigate the potential impact of a mild endotoxemia during pregnancy on brain maturation and behavioral reactivity as well as the infants’ hormone and immune physiology.
Nine pregnant female rhesus monkeys (Macaca mulatta) were administered nanogram concentrations of lipopolysaccharide (LPS) on two consecutive days, 6 weeks before term, and their offspring were compared to nine control animals. When tested under arousing challenge conditions, infants from the LPS pregnancies were more behaviorally disturbed, including a failure to show a normal attenuation of startle responses on tests of prepulse inhibition.
Examination of their brains at 1 year of age with magnetic resonance imaging (MRI) revealed the unexpected finding of a significant 8.8% increase in global white matter volume distributed across many cortical regions compared to controls.
More selective changes in regional gray matter volume and cortical thickness were noted in parietal, medial temporal, and frontal areas.
While inhibited neural growth has been described previously after prenatal infection and LPS administration at higher doses in rodents, this low dose endotoxemia in the monkey is the first paradigm to produce a neural phenotype associated with augmented gray and white matter growth.