NEURAL CORRELATES OF PERCEPTUAL EXPERTISE IN AUTISM

Background: Failure to look at people is an early symptom of autism, and individuals with autism exhibit anomalous face recognition, face scanning, and face-related brain activity throughout the lifespan. These deficits have been posited to reflect a lack of expertise resulting from limited social motivation and inattention to faces during development. This hypothesis presupposes an intact capacity for development of perceptual expertise given sufficient attention, interest, and exposure. This notion is difficult to examine because common areas of expertise among individuals with autism are rare. The current study examined brain response to letters of the alphabet as a neurophysiological marker of perceptual expertise.

Objectives: To investigate electrophysiological indices of perceptual expertise for non-social stimuli in individuals with autism.

Methods: High-density event-related potentials (ERPs; 256 channel Geodesic Sensor Net) were recorded from high-functioning adolescents with autism and typically-developing peers matched for age, sex, IQ, and handedness. Participants viewed social and non-social “expert” versus “non-expert” stimuli (human faces versus houses, Roman letters versus pseudoletters). Peak amplitude and latency were extracted for a negative component at 170 milliseconds over lateral posterior scalp (N170).

Results: Typical individuals exhibited enhanced N170 amplitude to both faces (versus houses; right lateralized) and Roman letters (versus pseudoletters; left lateralized), reflecting perceptual expertise for both classes of stimuli. Between-group comparisons indicated atypical ERP response to faces among individuals with autism but comparable response patterns for letters. Analyses in progress will examine correlations among ERP parameters and behavioral measures of letter and face perception.

Conclusions: Results concord with previous studies demonstrating anomalous face-related brain activity in autism. This is the first study to demonstrate intact development of perceptual expertise for letters in individuals with autism. Results are consistent with the hypothesis that face processing deficits in autism derive from developmental inattention to faces secondary to core impairments in social behavior.