Abnormal asymmetry in language association cortex in autism

TLDR

Autism is a neurodevelopmental disorder marked by cognitive, language, and social deficits, yet prior imaging studies have not examined language‑related cortex, despite its involvement in visual face processing. The study scanned 16 autistic and 15 control boys (ages 7–11, IQ > 80), segmented gray and white matter, parcellated cortex into 48 gyral divisions per hemisphere, and assessed asymmetry in language‑related frontal and temporal regions a priori and across all regions post hoc. Autistic boys showed a reversal of frontal language‑related cortical asymmetry (right‑dominant in autism versus left‑dominant in controls) and a left‑sided posterior temporal fusiform gyrus, with other regions trending right‑sided, suggesting that abnormal asymmetry in language and face‑processing areas may underlie language and social disturbances in autism.

Abstract

Abstract Autism is a neurodevelopmental disorder affecting cognitive, language, and social functioning. Although language and social communication abnormalities are characteristic, prior structural imaging studies have not examined language‐related cortex in autistic and control subjects. Subjects included 16 boys with autism (aged 7–11 years), with nonverbal IQ greater than 80, and 15 age‐ and handedness‐matched controls. Magnetic resonance brain images were segmented into gray and white matter; cerebral cortex was parcellated into 48 gyral‐based divisions per hemisphere. Asymmetry was assessed a priori in language‐related inferior lateral frontal and posterior superior temporal regions and assessed post hoc in all regions to determine specificity of asymmetry abnormalities. Boys with autism had significant asymmetry reversal in frontal language‐related cortex: 27% larger on the right in autism and 17% larger on the left in controls. Only one additional region had significant asymmetry differences on post hoc analysis: posterior temporal fusiform gyrus (more left‐sided in autism), whereas adjacent fusiform gyrus and temporooccipital inferior temporal gyrus both approached significance (more right‐sided in autism). These inferior temporal regions are involved in visual face processing. In boys with autism, language and social/face processing–related regions displayed abnormal asymmetry. These structural abnormalities may relate to language and social disturbances observed in autism.