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

The magnocellular deficit theory of dyslexia: the evidence from contrast sensitivity A number of authors have made the claim that dyslexia is the result of a deficit in the magnocellular part of the visual system. Most of the evidence cited in support of this claim is from contrast sensitivity studies. The present review surveys this evidence. The result of this survey shows that the support for the magnocellular deficit theory is equivocal. In the case of spatial contrast sensitivity there clearly are results that are consistent with the magnocellular deficit theory; however, these results are outnumbered both by studies that have found no loss of sensitivity and by studies that have found contrast sensitivity reductions that are inconsistent with a magnocellular deficit. Many of the studies of temporal contrast sensitivity are also difficult to reconcile with a magnocellular deficit. The evidence from studies of contrast sensitivity is therefore highly conflicting with regard to the magnocellular system deficit theory of dyslexia. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Vision Research Elsevier

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

Vision Research, Volume 40 (1) – Jan 1, 2000

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Publisher
Elsevier
Copyright
Copyright © 1999 Elsevier Science Ltd
ISSN
0042-6989
eISSN
1878-5646
DOI
10.1016/S0042-6989(99)00170-4
Publisher site
See Article on Publisher Site

Abstract

A number of authors have made the claim that dyslexia is the result of a deficit in the magnocellular part of the visual system. Most of the evidence cited in support of this claim is from contrast sensitivity studies. The present review surveys this evidence. The result of this survey shows that the support for the magnocellular deficit theory is equivocal. In the case of spatial contrast sensitivity there clearly are results that are consistent with the magnocellular deficit theory; however, these results are outnumbered both by studies that have found no loss of sensitivity and by studies that have found contrast sensitivity reductions that are inconsistent with a magnocellular deficit. Many of the studies of temporal contrast sensitivity are also difficult to reconcile with a magnocellular deficit. The evidence from studies of contrast sensitivity is therefore highly conflicting with regard to the magnocellular system deficit theory of dyslexia.

Journal

Vision ResearchElsevier

Published: Jan 1, 2000

References

  • The presence of a magnocellular defect depends on the type of dyslexia
    Borsting, E.; Ridder, W.H.; Dudeck, K.; Kelley, C.; Matsui, L.; Motoyama, J.
  • Selective depression of motion sensitivity during saccades
    Burr, D.C.; Holt, J.; Johnstone, J.R.; Ross, J.
  • Temporal impulse response functions for luminance and colour during saccades
    Burr, D.C.; Morrone, M.C.
  • Contrast sensitivity and coherent motion detection measured at photopic luminance levels in dyslexics and controls
    Cornelissen, P.; Richardson, A.; Mason, A.; Fowler, S.; Stein, J.
  • Magnocellular visual function and children's single word reading
    Cornelissen, P.; Hansen, P.C.; Hutton, J.L.; Evangelinou, V.; Stein, J.F.
  • Psychophysical evidence for a magnocellular pathway deficit in dyslexia
    Demb, J.B.; Boynton, G.M.; Best, M.; Heeger, D.J.
  • Spatial and temporal contrast sensitivities of neurons in lateral geniculate nucleus of Macaque
    Derrington, A.M.; Lennie, P.
  • Visual and visuomotor performance in dyslexic children
    Felmingham, K.L.; Jakobson, L.S.
  • Contrast sensitivity in dyslexia
    Gross-Glenn, K.; Skottun, B.C.; Glenn, W.; Kushch, A.; Lingua, R.; Dunbar, M.; Jallad, B.; Lubs, H.A.; Levin, B.; Rabin, M.; Parke, L.A.; Duara, R.
  • Psychophysical evidence for sustained and transient detectors in human vision
    Kulikowski, J.J.; Tolhurst, D.J.
  • How parallel are the primate visual pathways?
    Merigan, W.H.; Maunsell, J.H.R.
  • Visual sensitivity and parallel retinocortical channels
    Shapley, R.
  • Some remarks on the magnocellular deficit theory of dyslexia
    Skottun, B.C.

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