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Assessing Dyslexia at Six Year of Age
Published on: May 1, 2020
Dyslexia: a deficit in visuo-spatial attention, not in phonological processing.
Trichur R Vidyasagar1, Kristen Pammer
1Department of Optometry & Vision Sciences, University of Melbourne, Parkville, Vic 3010, Australia. trv@unimelb.edu.au
Trends in Cognitive Sciences
|January 19, 2010
Summary
Developmental dyslexia may stem from visual processing issues, not just sound-based (phonological) deficits. Poor visual coding impacts letter scanning, affecting reading and phonemic awareness development.
Area of Science:
- Neuroscience
- Developmental Psychology
- Ophthalmology
Background:
- Developmental dyslexia affects 10% of the population.
- Phonological deficits are traditionally considered the primary cause of reading impairment in dyslexia.
- Emerging evidence suggests a link between visual (orthographic) coding and dyslexia.
Purpose of the Study:
- To investigate the role of visual processing deficits in developmental dyslexia.
- To propose an alternative model where visual coding impairments precede phonological issues.
- To explore the contribution of attentional mechanisms in the dorsal visual stream to reading development.
Main Methods:
- Review of existing literature on dyslexia and visual processing.
- Theoretical modeling of attentional mechanisms in the dorsal visual stream.
- Analysis of the cascade effects of impaired visual scanning on reading-related skills.
Main Results:
- Phonological deficits may be a consequence, not the cause, of impaired visual (orthographic) coding.
- Attentional deficits in the dorsal visual stream can lead to poor serial letter scanning.
- This visual processing impairment can result in difficulties with grapheme-phoneme translation and phonemic awareness.
Conclusions:
- The core deficit in dyslexia may lie within the visual system, specifically in attentional mechanisms controlling visual scanning.
- This perspective offers a new framework for understanding dyslexia's origins.
- It opens avenues for novel early diagnostic and therapeutic strategies targeting visual processing.
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