The magnocellular deficit theory of dyslexia: the evidence from contrast sensitivity

Skottun, Bernt C.

doi:10.1016/s0042-6989(99)00170-4

Cited by 353 publications

(200 citation statements)

References 65 publications

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“…Consequently impairment of the dorsal stream or the magnocellular system has been implicated following reports of high motion coherence thresholds (Atkinson et al, 1997;Hansen et al, 2001;Milne et al, 2002;Spencer et al, 2000;Stein & Walsh, 1997). However, others have challenged the inference of a purely magnocellular impairment from high motion coherence thresholds (Bertone et al, 2003;Skottun, 2000), and, as was noted in the Introduction, there is no direct physiological evidence of magnocellular abnormality in autism. Recent research has highlighted the influence of attention in early vision such as stereoscopic depth (Rose, Bradshwaw, & Hibbard, 2003) and motion perception (Chaudhuri, 1990).…”

Section: Discussionmentioning

confidence: 99%

Motion and Form Coherence Detection in Autistic Spectrum Disorder: Relationship to Motor Control and 2:4 Digit Ratio

Milne

White²,

Campbell³

et al. 2006

J Autism Dev Disord

125

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Children with autistic spectrum disorder and controls performed tasks of coherent motion and form detection, and motor control. Additionally, the ratio of the 2nd and 4th digits of these children, which is thought to be an indicator of foetal testosterone, was measured. Children in the experimental group were impaired at tasks of motor control, and had lower 2D:4D than controls. There were no group differences in motion or form detection. However a sub-group of children with autism were selectively impaired at motion detection. There were significant relationships between motion coherence detection and motor control in both groups of children, and also between motion detection, fine motor control and 2D:4D in the group of children with autistic spectrum disorder.

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Section: Discussionmentioning

confidence: 99%

Motion and Form Coherence Detection in Autistic Spectrum Disorder: Relationship to Motor Control and 2:4 Digit Ratio

Milne

White²,

Campbell³

et al. 2006

J Autism Dev Disord

125

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“…[183][184][185][186][187] The studies supporting this theory are outnumbered by studies that have found no loss of contrastsensitivity and other studies that have found contrast-sensitivity reductions or other findings inconsistent with a magnocellular deficit. [188][189][190][191][192][193][194][195][196][197][198][199][200][201] Thus, the evidence in support of the magnocellular theory is equivocal at best. Amitay et al 191 found that although some (6 of 30) subject with dyslexia showed impaired magnocellular function, they consistently showed impaired performance in auditory and nonmagnocellular visual tasks.…”

Section: Magnocellular Deficit Theorymentioning

confidence: 99%

Learning Disabilities, Dyslexia, and Vision

Handler¹,

Fierson²

2011

Pediatrics

157

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Learning disabilities constitute a diverse group of disorders in which children who generally possess at least average intelligence have problems processing information or generating output. Their etiologies are multifactorial and reflect genetic influences and dysfunction of brain systems. Reading disability, or dyslexia, is the most common learning disability. It is a receptive language-based learning disability that is characterized by difficulties with decoding, fluent word recognition, rapid automatic naming, and/or reading-comprehension skills. These difficulties typically result from a deficit in the phonologic component of language that makes it difficult to use the alphabetic code to decode the written word. Early recognition and referral to qualified professionals for evidence-based evaluations and treatments are necessary to achieve the best possible outcome. Because dyslexia is a language-based disorder, treatment should be directed at this etiology. Remedial programs should include specific instruction in decoding, fluency training, vocabulary, and comprehension. Most programs include daily intensive individualized instruction that explicitly teaches phonemic awareness and the application of phonics. Vision problems can interfere with the process of reading, but children with dyslexia or related learning disabilities have the same visual function and ocular health as children without such conditions. Currently, there is inadequate scientific evidence to support the view that subtle eye or visual problems cause or increase the severity of learning disabilities. Because they are difficult for the public to understand and for educators to treat, learning disabilities have spawned a wide variety of scientifically unsupported vision-based diagnostic and treatment procedures. Scientific evidence does not support the claims that visual training, muscle exercises, ocular pursuit-and-tracking exercises, behavioral/perceptual vision therapy, “training” glasses, prisms, and colored lenses and filters are effective direct or indirect treatments for learning disabilities. There is no valid evidence that children who participate in vision therapy are more responsive to educational instruction than children who do not participate.

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“…Although numerous studies have investigated the spatial frequency sensitivities shown by dyslexic and non-dyslexic readers (for a review, see Skottun, 2000), the effectiveness of the spatial frequency content of text for fast and slow skilled adult reading remains to be revealed. So far, direct information on this issue has been provided by Patching and Jordan (2005a) and their findings suggest that briefly-presented single words, filtered to contain only certain spatial frequencies, are identified equally accurately by fast and slow readers.…”

mentioning

confidence: 99%

Fast and slow readers and the effectiveness of the spatial frequency content of text: Evidence from reading times and eye movements.

Jordan

Dixon

McGowan

et al. 2016

Journal of Experimental Psychology: Human Perception and Perfor

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Text contains a range of different spatial frequencies but the effectiveness of spatial frequencies for normal variations in skilled adult reading ability is unknown. Accordingly, young skilled adult readers showing fast or slow reading ability read sentences displayed as normal or filtered to contain only very low, low, medium, high, or very high spatial frequencies. Reading times and eye movement measures of fixations and saccades assessed the effectiveness of these displays for reading. Reading times showed that, for each reading ability, medium, high, and very high spatial frequencies were all more effective than lower spatial frequencies. Indeed, for each reading ability, reading times for normal text were maintained when text contained only medium, high, or very high spatial frequencies. However, reading times for normal text and for each spatial frequency were all substantially shorter for fast readers than for slow readers, and this advantage for fast readers was similar for normal, medium, high, and very high spatial frequencies but much larger for low and very low spatial frequencies. In addition, fast readers made fewer and shorter fixations, fewer and shorter regressions, and longer forward saccades, than slow readers, and these differences were generally similar in size for normal, medium, high, and very high spatial frequencies, but larger when spatial frequencies were lower. These findings suggest that fast and slow adult readers can each use a range of different spatial frequencies for reading but fast readers make more effective use of these spatial frequencies and especially those that are lower.

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The magnocellular deficit theory of dyslexia: the evidence from contrast sensitivity

Cited by 353 publications

References 65 publications

Motion and Form Coherence Detection in Autistic Spectrum Disorder: Relationship to Motor Control and 2:4 Digit Ratio

Motion and Form Coherence Detection in Autistic Spectrum Disorder: Relationship to Motor Control and 2:4 Digit Ratio

Learning Disabilities, Dyslexia, and Vision

Fast and slow readers and the effectiveness of the spatial frequency content of text: Evidence from reading times and eye movements.

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