Abstract
Many studies have suggested that children with developmental dyslexia (DD) not only show phonological deficit but also have difficulties in visual processing, especially in non-alphabetic languages such as Chinese. However, mechanisms underlying this impairment in vision are still unclear. Visual magnocellular deficit theory suggests that the difficulties in the visual processing of dyslexia are caused by the dysfunction of the magnocellular system. However, some researchers have pointed out that previous studies supporting the magnocellular theory did not control for the role of “noise”. The visual processing difficulties of dyslexia might be related to the noise exclusion deficit. The present study aims to examine these two possible explanations via two experiments. In experiment 1, we recruited 26 Chinese children with DD and 26 chronological age–matched controls (CA) from grades 3 to 5. We compared the Gabor contrast sensitivity between the two groups in high-noise and low-noise conditions. Results showed a significant between-group difference in contrast sensitivity in only the high-noise condition. In experiment 2, we recruited another 29 DD and 29 CA and compared the coherent motion/form sensitivity in the high- and low-noise conditions. Results also showed that DD exhibited lower coherent motion and form sensitivities than CA in the high-noise condition, whereas no evidence was observed that the group difference was significant in the low-noise condition. These results suggest that Chinese children with dyslexia have noise exclusion deficit, supporting the noise exclusion hypothesis. The present study provides evidence for revealing the visual dysfunction of dyslexia from the Chinese perspective. The nature of the perceptual noise exclusion and the relationship between the two theoretical hypotheses are discussed.
Highlights
The main feature of developmental dyslexia (DD) is a specific and significant impairment in the acquisition of reading skills that is not solely accounted for by mental age, visual acuity problems, or inadequate schooling (World Health Organization, 2011)
None of the main effects and no interaction was found. These results indicated that Chinese children with dyslexia had noise exclusion deficit, supporting the noise exclusion hypothesis
This suggests that Chinese children with dyslexia have noise exclusion deficit, whether it is related to motion or not, supporting the noise exclusion hypothesis
Summary
The main feature of developmental dyslexia (DD) is a specific and significant impairment in the acquisition of reading skills that is not solely accounted for by mental age, visual acuity problems, or inadequate schooling (World Health Organization, 2011). Some researchers believe that the specific reading impairments might be traced to some general perceptual processing problems, such as auditory temporal processing impairment (Tallal, 2004), visual magnocellular deficit (Stein, 1997, 2001, 2014), and cerebellar deficit (Nicolson et al, 2001; Nicolson and Fawcett, 2007). Many studies found impaired visual magnocellular-dorsal pathway function in dyslexics by means of behavioral and neuroimaging measurements (Boets et al, 2011; Jednoróg et al, 2011), which confirmed the magnocellular theory. Sperling et al (2005, 2006) pointed out that some previous studies that found magnocellular-dorsal deficits in dyslexics used stimuli with noisy conditions, so they assumed that the visual difficulties in DD might be associated with a noise exclusion deficit rather than magnocellular pathway deficit
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
