Difficulties with language acquisition and communication are often found in individuals with ASD. Imaging studies show atypical neural activation and lateralization during language tasks and suggest abnormal age-related changes in language lateralization. Despite these findings, the longitudinal development of cortical areas and white matter underlying auditory and language function are unknown.
The purpose of this longitudinal study was to examine developmental changes in an area involved in auditory and early language processing: the primary auditory cortex or Heschl’s gyrus (HG). Using magnetic resonance imaging (MRI), volumes of HG gray matter (GM) and HG white matter (WM) were examined during childhood and early adolescence in a group of individuals with ASD compared to typical development.
3T T1-weighted MRI images from 38 males with ASD and 12 typically developing male controls were examined at two timepoints acquired 2.5 years apart on average (mean age at Time 1: ASD=8.05 years, range 3-12; Control=9.42 years, range 4-12; mean age at Time 2: ASD=10.6 years, range 5-15; Control=11.75 years, range 6-15). HG was segmented manually on coronal MRI images using ITK-SNAP and longitudinal changes in HG GM and WM were measured. The ASD group was further examined by comparing HG changes in those participants with typical versus delayed language onset, as assessed by the ADI, and atypical auditory sensitivity measured by the Sensory Profile.
No significant between-group differences were found in mean HG GM or HG WM volumes at Time 1 or Time 2. A trend toward reduced volumetric changes in right HG GM was found in the ASD group compared to the typically developing group controlling for the effects of age, handedness, and head circumference (p=0.055). Longitudinal development of left HG WM was increased in ASD individuals with typical language onset versus delayed language onset (p=0.035). Longitudinal changes in left HG GM were decreased in individuals with atypical responses to questions of auditory sensitivity (p=0.04).
These findings suggest that in the absence of mean group differences at each timepoint, there may be differences in HG volumetric changes in ASD compared to typical development. We found increased longitudinal changes in the left HG in those individuals with ASD having typical language onset and typical auditory sensitivity profiles compared to those with delayed language onset and atypical auditory sensitivity, suggesting volumetric developmental differences in an area important for early auditory and language processing. The final analyses, that will include ASD and control participants with a 3rd timepoint, is in progress.
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