Autism or Autism Trait in the Normal Population? The Crisis of Defining Normal

The crisis of defining normal is just one of the issues that came to my mind after reading the recent paper “Autism Spectrum Traits in the Typical Population Predict Structure and Function in the Posterior Superior Temporal Sulcus” published May 3, 2010 in Cerebral Cortex.

Individuals with autism spectrum disorders are typically defined by impaired social interaction and communication, narrow interests, and repetitive behaviors. The severity of these characteristics varies broadly across individuals diagnosed with autism spectrum disorder. Are different traits of autism spectrum disorder associated with changes in brain structure and patterns of activation that are also seen in typical individuals?

Research described in the paper under review analyzed brain imaging data from 91 healthy individuals without autism spectrum disorders who also completed standardized questionnaires. The 50 item questionnaire is known as the autism spectrum quotient which is used to measure the degree of autism spectrum characteristics found within the typical population. A higher score indicates a greater extent of autism spectrum characteristics.

Results showed that those with higher scores on the questionnaire had a significant reduction in white matter volume in just one region of the brain known as the posterior part of the right superior temporal sulcus. Results also showed that individuals with higher scores displayed greater deactivation of the same region of the brain. The posterior part of the right superior temporal sulcus is known to be important for processing socially relevant stimuli and to be structurally and functionally impaired in people diagnosed with autism spectrum disorders.

These data provide evidence that typical healthy people present traits that are symptomatic in those diagnosed with autism spectrum disorders. Strikingly, the brain images of normal individuals with these traits displayed structural and functional brain anomalies like those seen in individuals diagnosed with autism spectrum disorders.

Other related blog posts:

Autism and the Brain: Recent Results from Brain Imaging Studies

Reduced Direct Eye Contact and Autism Spectrum Disorders: Reduced Orientation or Active Avoidance?

Abnormal Brain Growth in Toddlers Diagnosed with Autism