Abstract
Autism spectrum disorder (ASD) is a prevalent and fast-growing pervasive neurodevelopmental disorder worldwide. Despite the increasing prevalence of ASD and the breadth of research conducted on the disorder, a conclusive etiology has yet to be established and controversy still exists surrounding the anatomical abnormalities in ASD. In particular, structural asymmetries have seldom been investigated in ASD, especially in subcortical regions. Additionally, the majority of studies for identifying structural biomarkers associated with ASD have focused on small sample sizes. Therefore, the present study utilizes a large-scale, multi-site database to investigate asymmetries in the amygdala, hippocampus, and lateral ventricles, given the potential involvement of these regions in ASD. Contrary to prior work, we are not only computing volumetric asymmetries, but also shape asymmetries, using a new measure of asymmetry based on spectral shape descriptors. This measure represents the magnitude of the asymmetry and therefore captures both directional and undirectional asymmetry. The asymmetry analysis is conducted on 437 individuals with ASD and 511 healthy controls using T1-weighted MRI scans from the Autism Brain Imaging Data Exchange (ABIDE) database. Results reveal significant asymmetries in the hippocampus and the ventricles, but not in the amygdala, in individuals with ASD. We observe a significant increase in shape asymmetry in the hippocampus, as well as increased volumetric asymmetry in the lateral ventricles in individuals with ASD. Asymmetries in these regions have not previously been reported, likely due to the different characterization of neuroanatomical asymmetry and smaller sample sizes used in previous studies. Given that these results were demonstrated in a large cohort, such asymmetries may be worthy of consideration in the development of neurodiagnostic classification tools for ASD.
Highlights
Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder that begins in early childhood and persists throughout life
Multiple regression analyses were calculated to predict volumetric and shape asymmetries in the amygdala, hippocampus, and lateral ventricles based on diagnosis and sex, while controlling for age, scanning site, intracranial volume, and full-scale IQ (FSIQ)
Diagnosis had no significant effect on shape or volumetric asymmetry, sex was a significant predictor of shape asymmetry
Summary
Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder that begins in early childhood and persists throughout life. Extensive research utilizing magnetic resonance imaging (MRI) has been conducted to investigate structural and functional differences found in ASD, and various neuroanatomical differences have been proposed as potential biomarkers for the disorder (for a recent review, see Li et al, 2017). MRI has enabled researchers to search for neuroanatomical biomarkers and attempt to develop MRI-based classification algorithms and computer-aided diagnostic systems to facilitate diagnosis (Dekhil et al, 2017; Ecker et al., 2010; Ismail, 2016; Mateos-Perez et al, 2018; Mostapha et al, 2015; Nielsen et al, 2012; Plitt et al, 2014), findings of potential structural biomarkers for ASD have been mixed and partly inconclusive
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