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PLoS One. 2014 Mar 14;9(3):e90993. doi: 10.1371/journal.pone.0090993. eCollection 2014.

A different view on the checkerboard? Alterations in early and late visually evoked EEG potentials in Asperger observers.

Author information

Institute for Frontier Areas of Psychology and Mental Health, Freiburg, Germany; Eye Center, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.
PPD Germany GmbH & Co Kg, Karlsruhe, Germany.
Section for Experimental Neuropsychiatry, Clinic for Psychiatry & Psychotherapy, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.
Eye Center, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.



Asperger Autism is a lifelong psychiatric condition with highly circumscribed interests and routines, problems in social cognition, verbal and nonverbal communication, and also perceptual abnormalities with sensory hypersensitivity. To objectify both lower-level visual and cognitive alterations we looked for differences in visual event-related potentials (EEG) between Asperger observers and matched controls while they observed simple checkerboard stimuli.


In a balanced oddball paradigm checkerboards of two checksizes (0.6° and 1.2°) were presented with different frequencies. Participants counted the occurrence times of the rare fine or rare coarse checkerboards in different experimental conditions. We focused on early visual ERP differences as a function of checkerboard size and the classical P3b ERP component as an indicator of cognitive processing.


We found an early (100-200 ms after stimulus onset) occipital ERP effect of checkerboard size (dominant spatial frequency). This effect was weaker in the Asperger than in the control observers. Further a typical parietal/central oddball-P3b occurred at 500 ms with the rare checkerboards. The P3b showed a right-hemispheric lateralization, which was more prominent in Asperger than in control observers.


The difference in the early occipital ERP effect between the two groups may be a physiological marker of differences in the processing of small visual details in Asperger observers compared to normal controls. The stronger lateralization of the P3b in Asperger observers may indicate a stronger involvement of the right-hemispheric network of bottom-up attention. The lateralization of the P3b signal might be a compensatory consequence of the compromised early checksize effect. Higher-level analytical information processing units may need to compensate for difficulties in low-level signal analysis.

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