Brain activity during processing objects and pseudo-objects: Comparison between adult regular and dyslexic readers

• Published in: Clinical neurophysiology Vol. 122; no. 2; pp. 284 - 298
• Main Authors: Mayseless, Naama, Breznitz, Zvia
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ireland Ltd 01.02.2011; Elsevier
• Subjects: Adult; Age Factors; Biological and medical sciences; Brain - physiology; Dyslexia; Dyslexia - physiopathology; Early processing; Electrodiagnosis. Electric activity recording; Event-related potentials (ERP); Evoked Potentials - physiology; Female; Humans; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Nervous system; Neurology; Object recognition; Ophthalmology; Photic Stimulation - methods; Reaction Time - physiology; Reading; Vision disorders; Visual Perception - physiology; Young Adult; Dyslexia; Object recognition; Event-related potentials (ERP); Early processing; Reading disorder; Vision disorder; Central nervous system; Electrophysiology; Right hemisphere; Language disorder; Pictural drawing; Encephalon; Electrodiagnosis; Accuracy; Language; Left hemisphere; Computer; Tomography; Human; Data analysis; Communication disorder; Eye disease; Reaction time; Event evoked potential; Recognition
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2010.06.029

Abstract Objective The 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. Methods The 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. Results The 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. Conclusions The 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. Significance These 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.