Evidence for impaired integration-segmentation processes and slowed synchrony coding in dyslexics

Abstract

Using a primed figure-detection task we were able to reveal the existence of two distinct groups of dyslexics. One group is characterized by a significant impairment of visual integration-segmentation processes, resulting in slowed performance for the detection of a illusory Kanizsa-type figure in a matrix of distractor elements. These deficits appear to be produced by inefficient synchrony coding mechanisms. The second group of dyslexics shows slightly impaired integration-segmentation abilities. The results suggest a visual processing deficit apparent in a subgroup of dyslexics which is possibly based on slow magnocellular processing. The reported results are in agreement with previous findings reporting the existence of a distinct subgroup of dyslexics, which shows spatio-temporal processing deficits based on impairments of the magnocellular pathway in the visual system. Dyslexia is a pronounced difficulty or inability in learning to read and/or to spell, despite otherwise normal intellectual functions. It has been proposed that reading requires the coordination of many functions and processes, such as visual and semantic decoding. Reading disability is supposed to be based on the failure of this coordination due to single or multiple impairments in functions involved in the reading process.