Brain Advance Access originally published online on June 15, 2005
Brain 2005 128(10):2430-2441; doi:10.1093/brain/awh561
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Enhanced and diminished visuo-spatial information processing in autism depends on stimulus complexity
1 Visual Psychophysics and Perception Laboratory, École d'optométrie, Université de Montréal, C. P. 6128 Succursale Centre Ville, Montréal, H3C-3J7, Canada and 2 Clinique Spécialisée de l'Autisme, Hôpital Rivière-des-Prairies, 7070 boulevard Perras, Montréal, H1E-1A4, Canada
Correspondence to: Armando Bertone, Visual Psychophysics and Perception Laboratory, École d'optométrie, Université de Montréal, 3744 Jean-Brillant, Montréal, Canada, H3T IPI E-mail: armando.bertone{at}umontreal.ca
Visuo-perceptual processing in autism is characterized by intact or enhanced performance on static spatial tasks and inferior performance on dynamic tasks, suggesting a deficit of dorsal visual stream processing in autism. However, previous findings by Bertone et al. indicate that neuro-integrative mechanisms used to detect complex motion, rather than motion perception per se, may be impaired in autism. We present here the first demonstration of concurrent enhanced and decreased performance in autism on the same visuo-spatial static task, wherein the only factor dichotomizing performance was the neural complexity required to discriminate grating orientation. The ability of persons with autism was found to be superior for identifying the orientation of simple, luminance-defined (or first-order) gratings but inferior for complex, texture-defined (or second-order) gratings. Using a flicker contrast sensitivity task, we demonstrated that this finding is probably not due to abnormal information processing at a sub-cortical level (magnocellular and parvocellular functioning). Together, these findings are interpreted as a clear indication of altered low-level perceptual information processing in autism, and confirm that the deficits and assets observed in autistic visual perception are contingent on the complexity of the neural network required to process a given type of visual stimulus. We suggest that atypical neural connectivity, resulting in enhanced lateral inhibition, may account for both enhanced and decreased low-level information processing in autism.
Key Words: autism, enhanced perceptual functioning; first and second order information processing; lateral inhibition; neural networks; perception; visuo-spatial information processing
Abbreviations: ADI = autism diagnostic interview; ADOS-G = autistic diagnostic observation schedule general; FXS = fragile X syndrome; HFA = high-functioning persons with autism; PEST = parameter estimation by sequential testing; TD = typically developing
Received January 11, 2005. Revised May 4, 2005. Accepted May 12, 2005.
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