Abnormal asymmetry in language association cortex in autism

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 languagerelated 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.

Electrophysiological signatures: Magnetoencephalographic studies of the neural correlates of language impairment in autism spectrum disorders

“…At 200-300ms, problems with change detection and rapid temporal processing are apparent. Hemispheric differences also exist, with some suggestion of right hemisphere abnormalities, perhaps consistent with emerging evidence from structural studies which implicate right hemisphere substrates in ASD (De Fosse et al, 2004;Herbert et al, 2002). That said, atypical left hemispheric responses in mismatch and RTP paradigms are also observed in ASD, reflective of language impairment.…”

Three-dimensional mapping of the lateral ventricles in autism

“…While this could be related to abnormalities of asymmetry reported in other brain imaging studies of autism (e.g., Herbert et al, 2002), statistical assessment of asymmetry did not show significant group differences.…”

Neonatal serotonin depletion alters behavioral responses to spatial change and novelty

“…Head circumference and cortical volume are increased in young children (2-6 years of age) with autism (Piven et al, 1996;Courchesne et al, 2001;Sparks et al, 2002) during the same time that cortical 5-HT synthesis lags behind normal. Moreover, numerous studies show structural alterations in the cerebral cortex of children with autism (Bailey et al, 1998;Casanova et al, 2002;Herbert et al, 2002;Levitt et al, 2003). Such changes in the size and architecture of important cortical processing areas may underlie functional deficits in the development of cortical sound processing (Gage et al, 2003), visuo-motor maps (Mueller et al, 2003) and face recognition Dawson et al, 2002) that are observed in autism.…”