Please use this identifier to cite or link to this item: https://hdl.handle.net/10316/108220
Title: Visual Perception and Reading: New Clues to Patterns of Dysfunction Across Multiple Visual Channels in Developmental Dyslexia
Authors: Rodrigues, Ana Pina 
Rebola, José 
Jorge, Helena 
Ribeiro, Maria José 
Pereira, Marcelino 
van Asselen, Marieke
Castelo-Branco, Miguel 
Keywords: dyslexia; reading disorder; visual perception; magnocellular-dorsal stream; ventral stream
Issue Date: 1-Jan-2017
Publisher: Association for Research in Vision and Ophthalmology
Project: PTDC/SAU-NSC/113471/2009 
SFRH/BD/75083/ 2010 
info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UID/NEU/04539/2013/PT 
Serial title, monograph or event: Investigative Ophthalmology and Visual Science
Volume: 58
Issue: 1
Abstract: PURPOSE. The specificity of visual channel impairment in dyslexia has been the subject of much controversy. The purpose of this study was to determine if a differential pattern of impairment can be verified between visual channels in children with developmental dyslexia, and in particular, if the pattern of deficits is more conspicuous in tasks where the magnocellular–dorsal system recruitment prevails. Additionally, we also aimed at investigating the association between visual perception thresholds and reading. METHODS. In the present case–control study, we compared perception thresholds of 33 children diagnosed with developmental dyslexia and 34 controls in a speed discrimination task, an achromatic contrast sensitivity task, and a chromatic contrast sensitivity task. Moreover, we addressed the correlation between the different perception thresholds and reading performance, as assessed by means of a standardized reading test (accuracy and fluency). Group comparisons were performed by the Mann-Whitney U test, and Spearman’s rho was used as a measure of correlation. RESULTS. Results showed that, when compared to controls, children with dyslexia were more impaired in the speed discrimination task, followed by the achromatic contrast sensitivity task, with no impairment in the chromatic contrast sensitivity task. These results are also consistent with the magnocellular theory since the impairment profile of children with dyslexia in the visual threshold tasks reflected the amount of magnocellular–dorsal stream involvement. Moreover, both speed and achromatic thresholds were significantly correlated with reading performance, in terms of accuracy and fluency. Notably, chromatic contrast sensitivity thresholds did not correlate with any of the reading measures. CONCLUSIONS. Our evidence stands in favor of a differential visual channel deficit in children with developmental dyslexia and contributes to the debate on the pathophysiology of reading impairments.
URI: https://hdl.handle.net/10316/108220
ISSN: 1552-5783
DOI: 10.1167/iovs.16-20095
Rights: openAccess
Appears in Collections:I&D IBILI - Artigos em Revistas Internacionais
FMUC Medicina - Artigos em Revistas Internacionais
FPCEUC - Artigos em Revistas Internacionais

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