title: Independent component analysis reveals atypical electroencephalographic activity during visual perception in individuals with autism.
abstract: 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 alpha- and gamma-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 alpha- and gamma-band power, and time to peak alpha-band power was reduced, in the participants with ASD. Induced alpha-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.
authors.affiliation: Department of Psychology, The University of Sheffield, Sheffield, United Kingdom. E.Milne@Sheffield.ac.uk
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Milne
authors.forename: Alison
authors.initials: A
authors.lastname: Scope
authors.forename: Olivier
authors.initials: O
authors.lastname: Pascalis
authors.forename: David
authors.initials: D
authors.lastname: Buckley
authors.forename: Scott
authors.initials: S
authors.lastname: Makeig
mesh_terms: D000293:Adolescent; D020817:Asperger Syndrome / Q000503:physiopathology*; D001321:Autistic Disorder / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography / Q000523:psychology*; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D012815:Signal Processing, Computer-Assisted; D014796:Visual Perception