Abnormal activation of face processing systems at early and intermediate latency in individuals with autism spectrum disorder: a magnetoencephalographic study

The neurological basis of developmental psychopathology in autism is a matter of intense debate. Magnetoencephalography (MEG) was used to study the neuronal responses associated with the processing of faces in 12 able adults with autism spectrum disorders (ASD), performing image categorization and image identification tasks. The neuromagnetic data were analysed using nonparametric time-series analysis and equivalent current dipole estimation. Comparison data were obtained from 22 normally developing adults. In individuals with ASD, the neural responses to images of faces, observed in right extrastriate cortices at approximately 145 ms after stimulus onset, were significantly weaker, less lateralized and less affected by stimulus repetition than in control subjects. Early latency (30-60 ms) responses to face images, over right anterior temporal regions, differed significantly between the two subject groups in the image identification task. No such difference was observed for images of mugs or meaningless geometrical patterns. These findings suggest that, during the course of development in individuals with ASD, the cortical activity associated with the processing of human faces assumes a different-from-normal localization in extrastriate brain regions. This abnormal localization may be associated with unusual, but nevertheless face-specific, fast processing pathways.