Impaired white matter integrity and social cognition in high functioning autism spectrum disorders : a diffusion tensor imaging study

Abstract

Autism spectrum disorders (ASDs) are neurodevelopmental disorders, characterized by impaired social interaction; impaired communication; and repetitive, restrictive, and stereotyped interests, activities, and behaviors. Although the etiology of autism is unknown, recent studies have provided convincing evidence that many of the cognitive and social deficits of ASDs may be caused by abnormal connectivity between brain networks. In this study, we aimed to determine whether patients with ASDs have less intact functional connectivity between cortico-cortical areas involved in social cognition than a normally developing control group. We assessed severity of impairment of social interaction and communication by subscales of the Autism Diagnostic Interview-Revised-Korean version (ADI-R-K). Subsequently, we investigated the relationship between the degree of impaired connectivity in relevant brain areas and severity of the symptom scores. Method: Diffusion tensor imaging (DTI) is the best currently available method for assessing white matter integrity in the human brain and does not require any intrusive interventions. Fractional anisotropy (FA) is an index of the integrity of white matter in DTI studies. In this study, we compared individuals with high functioning autism (9 to 14 years old) to normal controls using DTI to determine whether the high functioning autism group demonstrated decreased FA in association fiber tracts. We also evaluated the relationships between FA and ADI-R-K scores for social interaction, communication and stereotypic behaviors. Result: There were 22 study participants, including 9 with high functioning autism (8 boys and 1 girl) and 13 normally developing individuals (all boys). The 2 groups were not significantly different in age or full-scale intelligence quotient, and all subjects were right-handed. Tract based spatial statistics (TBSS) analysis performed after excluding age and gender revealed significantly lower FA in the left inferior fronto-occipital fasciculus, left superior longitudinal fasciculus, left inferior longitudinal fasciculus, and right amygdala. Significant negative correlations were found between social interaction scores of the ADI-R-K and FA of the left inferior fronto-occipital fasciculus, left inferior longitudinal fasciculus, and left superior longitudinal fasciculus in the high functioning autism group, suggesting that the severity of white matter impairment in these regions was related to poor social cognition. FA of significantly affected regions in the high functioning autism group also showed negative correlations with communication and stereotypic behavior scores of the ADI-R-K. Conclusion: In this study, we conclude that individuals with high functioning autism exhibited impaired neural connectivity between the brain regions involved in social cognition.