Independent Component Analysis Reveals Atypical Electroencephalographic Activity During Visual Perception in Individuals with Autism
Received 23 January 2007; received in revised form 13 July 2008; accepted 24 July 2008. published online 09 September 2008.
Background
Individuals with autistic spectrum disorder (ASD) experience atypical visual perception, yet the etiology of this remains unknown. The aim of this study was to investigate the neural correlates of visual perception in individuals with and without ASD by carrying out a detailed analysis of the dynamic brain processes elicited by perception of a simple visual stimulus.
Methods
We investigated perception in 20 individuals with ASD and 20 control subjects with electroencephalography (EEG). Visual evoked potentials elicited by Gabor patches of varying spatial frequency and stimulus-induced changes in α- and γ-frequency bands of independent components were compared in those with and without ASD.
Results
By decomposing the EEG data into independent components, we identified several processes that contributed to the average event related potential recorded at the scalp. Differences between the ASD and control groups were found only in some of these processes. Specifically, in those components that were in or near the striate or extrastriate cortex, stimulus spatial frequency exerted a smaller effect on induced increases in α- and γ-band power, and time to peak α-band power was reduced, in the participants with ASD. Induced α-band power of components that were in or near the cingulate gyrus was increased in the participants with ASD, and the components that were in or near the parietal cortex did not differ between the two groups.
Conclusions
Atypical processing is evident in individuals with ASD during perception of simple visual stimuli. The implications of these data for existing theories of atypical perception in ASD are discussed.
ABSTRACT