Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by difficulties with social interactions. Within the brain, distant brain regions communicate by sending signals to one another through tracts. These tracts are much like telephone lines; they are physical connections that facilitate rapid communication between brain areas (telephones) separated by distance. Also like telephone lines, differences in tract construction can result in differences in their ability to communicate signals effectively. It has been postulated that individuals with ASD may have structural differences in the brain’s tracts, which might explain relative social difficulties.
In this study, we used specialized MRI (magnetic resonance imaging) scans to investigate the structure of brain tracts in individuals with ASD and to determine if tract structure is related to social symptoms. To do this, we scanned 25 youth with ASD and 27 healthy age-matched controls. We also had parents of participants with ASD complete a questionnaire which provided us with a score that described the severity of their children’s symptoms. Next we compared the brain tract structure between groups and looked for correlations between tract structure and symptom scores in the individuals with ASD.
We found that tracts in individuals with ASD had reduced density of fiber bundles (smaller units that make up the tract) relative to the control participants. Furthermore, in participants with ASD, we found that lower fiber bundle density was associated with more severe social symptoms. These findings add to our understanding of the physiology of ASD and could help aid in the development of effective treatment for social symptoms.