Heschl's Gyrus and Planum Temporale Volume in Autism: Does Morphology Reflect Language Function?

Background: Functional imaging studies of language and auditory processing in autism show abnormalities in the location and asymmetry of neural activation. Despite the striking clinical significance of language impairment and auditory sensitivity in autism, the development of the cortical regions underling these deficits remains largely unknown. Objectives: The present study compares volume and asymmetry of the primary auditory cortex (Heschl's gyrus) and auditory association cortex (planum temporale) in children with autism to typically developing children using 3 Tesla structural MRI. We also investigate how speech onset and language function are related to Heschl's gyrus and planum temporale structure in autism. Methods: Manual segmentation of Heschl's gyrus and planum temporale of 17 male individuals with autism and 12 male control participants (age range 4-12 years; mean age: autism=8.3, control=8.7) were made on coronal 3T MRI images using itk-SNAP. The autism group was further divided into those with normal language onset or delayed language onset assessed with the ADI-R. Group differences in volume and asymmetry were examined. Results: No autism-control differences were found in Heschl's gyrus or planum temporale volume or asymmetry controlling for age and performance IQ. Interestingly, the individuals with autism with delayed language onset (n=8) showed reduced Heschl's gyrus L>R asymmetry (p=.002) compared to the autism group with normal language onset (n=9). This difference was driven by larger volume in the right Heschl's gyrus in the delayed language onset autism group compared to the normal language onset autism group (p=.002). Data collection is ongoing and future analyses will examine Heschl's gyrus gray and white matter differences in a larger participant sample. Conclusions: These preliminary findings suggest abnormalities in the development of cortical regions responsible for early auditory and language processing in individuals with autism with aberrant language development. Results also suggest that differences in brain morphology may subdivide individuals with autism into meaningful subgroups. These cross-sectional findings will be combined with longitudinal data on this same group of participants to understand the structural development of cortical areas involved in early stages of language processing.