An early ERP signature reflects differences in visual processing between Asperger and control observers R Wörner1, L Tebartz van Elst, J Kornmeier2 |
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1Institute for Frontier Areas of Psychology and Mental Health, Germany |
| Background: Asperger Autism is a lifelong psychiatric condition with problems in social cognition, highly circumscribed interests and routines and also perceptual abnormalities with sensory hypersensitivity. To objectify such perceptual alterations we looked for differences in cognitive and early visual event-related potentials (EEG) between Asperger observers and matched controls. Methods: In a typical oddball paradigm checkerboards of two sizes were presented with different frequencies. Participants counted the occurrence times of the rare stimuli. We focused early visual ERP responses and the classical late P3b component. Results: A positive ERP component, 200 ms after stimulus onset (P200) and maximal at occipito-parietal midline electrodes, showed smaller amplitudes in Asperger observers compared to controls. This difference was most prominent with small checkerboards. The rare stimuli elicited a typical odball-P3b with maximal amplitudes at central electrodes. The P3b occurred earlier for small checkerboards and this latency difference was larger in Asperger observers compared to controls. Discussion: The P200 amplitude effect may reflect principle differences in early visual processing between the Asperger observers and normal controls. These differences get more obvious with detailedness of the stimulus (e.g. more edges in smaller squares) and seem to affect the timing of later, more cognitive processing steps (P3b latency-decrease). |
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