Previous research on structural abnormalities in Autism Spectrum Disorders (ASD) has largely focused on low-functioning or a broad spectrum of high- and low-functioning adult and adolescent populations. These studies have found reduced temporal, fusiform, and cerebellar grey matter and increases in frontal grey matter in ASD relative to control subjects. One study with school-aged high-functioning children showed increases in prefrontal, supramarginal and post central gyri with a reduction in the parahipppcampal gyrus in ASD relative to control subjects.
To examine differences in gray matter density between high-functioning 7-13 year old ASD children and IQ-matched typically developing controls (TD).
15 school-aged TD children and 15 children with ASD matched on age, IQ and gender-ratio (TD: FSIQ = 119, age = 10.4 years, 15 male; ASD: FSIQ = 121, age = 10.2 years, 11 male) were recruited for research studies conducted at Georgetown University. Structural images (MPRAGE) were collected for each subject and processed in SPM8 using the method for optimized voxel based morphometry (VBM). Two-Group t-tests were run between TD and ASD.
Children with ASD showed reduced grey matter in the right fusiform and left superior temporal gyrus (p<0.001, k=50). Further, they showed greater grey matter in the right middle temporal and right middle fusiform gyrus. These abnormalities did not correlate with IQ or ASD symptoms as measured by the Social Responsiveness Scale, ADI or ADOS.
Our findings converge with prior VBM studies of adults and low-functioning children/adolescents by showing reduced gray matter concentration in regions critical for processing social information. The consistency of differences in gray matter in the fusiform and temporal regions across studies suggests that changes to these regions are independent of age and IQ.