Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
3044981 | Clinical Neurophysiology | 2011 | 15 Pages |
ObjectiveThe role of visual processing deficits in dyslexia remains unclear and continues to stir controversy. Most studies to date have used alphabetic and or other language-dependent patterns. The current study compares how dyslexics and regular readers process non-alphabetic visual patterns.MethodsThe stimuli were black and white drawings, 50 meaningful (concrete objects) and 50 meaningless (pseudo-objects with no linguistic name) presented visually on a computer screen. Measures included behavioral accuracy and reaction time, event-related potential (ERP), and low resolution electromagnetic tomography (LORETA). The subjects were 15 dyslexic and 15 aged-matched regular readers.ResultsThe dyslexics exhibited significantly longer reaction time and shorter latencies of P1 and P2 components to both objects and pseudo-objects compared to the regular readers. Data from the LORETA solution analysis indicated significantly different brain activity between the two groups: both exhibited higher left hemisphere activation when viewing objects compared to pseudo-objects; and dyslexics exhibited lower left hemisphere activation when viewing objects and higher right hemisphere activation when viewing pseudo-objects during the early stages of processing.ConclusionsThe results support the notion that brain activation of dyslexic readers differs from that of the regular readers when processing non-alphabetic patterns, and that the differences appear from the early stage of processing.SignificanceThese results emphasize that differences in brain activity between dyslexic and regular readers can be seen even in a non-alphabetic task, and in early stages of processing.