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Teri Lawton; Direction discrimination training removes timing deficits in the dorsal pathway that impair reading ability. Journal of Vision 2009;9(8):821. doi: 10.1167/9.8.821.
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© ARVO (1962-2015); The Authors (2016-present)
Timing deficits resulting from sluggish magnocellular pathways are thought to underlie reading difficulties in dyslexics, those who have reading problems with no obvious neurological, sensory or ocular-motor deficits. Controlled validation studies in public schools showed that, for dyslexic children, reading fluency improved when children were trained, before directed reading, on direction discrimination 10 minutes twice a week for 15 weeks, but not when children were trained on word discrimination. In direction discrimination training, when only one level of background complexity was used, dyslexics' contrast sensitivity improved 5-fold and reading rates improved 2-fold on average. When 8 levels of background complexity were used, not only did contrast sensitivity improve 14-fold, but reading rates also improved 4-fold. Moreover, when direction discrimination training was administered individually using 14–16 complexity levels, more sessions, and was followed by training on reading fluency for 5 minutes using coached guided reading, reading rates improved 11-fold instead of only 4-fold. Furthermore, the more training on direction discrimination was administered, the more reading rates improved (p [[lt]]0.001). Significantly, the data from subsequent years show that these changes do not regress over time. These remarkable results from such a short amount of training can be explained in terms of removing the timing deficits in the dorsal pathway by tuning the sluggish magnocellular neurons over different backgrounds, so they are more sensitive, respond more quickly, and improve timing with linked parvocellular neurons. It is plausible to conjecture that sluggish magnocellular neurons cause a deficit in attentional focus, preventing the linked parvocellular neurons from isolating and sequentially processing the relevant information needed for reading. Direction discrimination training, optimal for activating the dorsal pathways at lower processing levels, improved reading fluency significantly, 4–11 fold. Data suggesting that direction discrimination training broadens the attention gateway, improving sequential processing, will also be discussed.
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