Abstract
Magnocellular (M) deficit theory points out that the core deficit of developmental dyslexia (DD) is the impairment in M pathway, which has been evidenced in many previous studies. Based on the M deficit, some researchers found that visual intervention focusing on M deficit improved dyslexics’ M function as well as reading abilities. However, the number and reliability of these training studies were limited. Therefore, the present study conducted an M-based visual-motor intervention on Chinese children with DD to investigate the relationship between M deficit and Chinese DD. Intervention programs included coherent motion detection, visual search, visual tracking, and juggling, which were related to M function. The results showed that M function and phonological awareness of training dyslexic group were improved to a normal level as age-matched normal children after intervention, while non-training dyslexics did not. It supported M deficit theory, and suggested M deficit might be the core deficit of Chinese DD.
Highlights
Developmental dyslexia (DD) is a neurobiological reading disorder
The results showed that M function and phonological awareness of training dyslexic group were improved to a normal level as age-matched normal children after intervention, while non-training dyslexics did not
M pathway starts from retinal M ganglion cells in retina, visual information is conveyed to the M layers of the dorsal lateral geniculate nucleus (LGN) of the thalamus
Summary
Developmental dyslexia (DD) is a neurobiological reading disorder. Individuals with DD have difficulties in accurate or fluent word recognition, spelling, and word decoding despite adequate instruction and intelligence (Lyon et al, 2003). Researchers have made efforts in studying on DD, the cause of DD remains controversial. Some researchers pointed out that the cause of DD could be traced back to a more general perceptual dysfunction. M pathway starts from retinal M ganglion cells in retina, visual information is conveyed to the M layers of the dorsal lateral geniculate nucleus (LGN) of the thalamus. Information was project to the primary visual cortex, and further transferred to the posterior parietal cortex (PPC) via the dorsal stream ( known as the “where” stream), which has been implicated in object localization, motion perception, visual attention, and goal-directed behavior. The dorsal stream includes middle temporal (MT) area, which is known to play a key role in motion perception and is activated when observers are presented with random dot kinematograms (RDKs) containing coherent motion (CM; Goodale and Westwood, 2004; Boden and Giaschi, 2007)
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