Brain Advance Access originally published online on January 11, 2008
Brain 2008 131(4):1013-1024; doi:10.1093/brain/awm321
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A neural substrate for atypical low-level visual processing in autism spectrum disorder
1Department of Child and Adolescent Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, 2Cognitive Neuroscience Group, Department of Psychology, University of Amsterdam, Amsterdam, 3The Netherlands Institute for Neuroscience, Amsterdam, The Netherlands, part of the Royal Academy of Arts and Sciences (KNAW) and 4Department of Neurocognition, Faculty of Psychology, Maastricht University, Maastricht, The Netherlands
Correspondence to: Myriam W. G. Vandenbroucke, University Medical Centre Utrecht, Department of Child and Adolescent Psychiatry, B01.201 Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. E-mail: m.w.g.vandenbroucke{at}umcutrecht.nl
An important characteristic of autism spectrum disorder (ASD) is increased visual detail perception. Yet, there is no standing neurobiological explanation for this aspect of the disorder. We show evidence from EEG data, from 31 control subjects (three females) and 13 subjects (two females) aged 16–28 years, for a specific impairment in object boundary detection in ASD, which is present as early as 120 ms after stimulus presentation. In line with a neural network model explicating the role of feedforward, horizontal and recurrent processing in visual perception, we can attribute this deficit to a dysfunction of horizontal connections within early visual areas. Interestingly, ASD subjects showed an increase in subsequent activity at lateral occipital sites (225 ms), which might reflect a compensational mechanism. In contrast, recurrent processing between higher and lower visual areas (around 260 ms), associated with the segregation between figure and background, was normal. Our results show specific neural abnormalities in ASD related to low-level visual processing. In addition, given the reconciliation between our findings and previous neuropathology and neurochemistry research, we suggest that atypical horizontal interactions might reflect a more general neural abnormality in this disorder.
Key Words: Asperger; horizontal connections; lateral inhibition; GABA; minicolumns
Abbreviations: ADI-R, autism diagnostic interview—revised; ADOS-G, autism diagnostic observation schedule—generic; ASD, autism spectrum disorder; CMS, common mode sense; DRL, driven right leg; ERP, electrophysiological recording; FDR, false discovery rate.
Received July 12, 2007. Revised December 1, 2007. Accepted December 12, 2007.
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