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Monica Giraldo, John P. Hegarty, Keith A. Schneider; Reduction of the lateral geniculate nucleus volume in subjects with dyslexia compared to matched controls. Journal of Vision 2012;12(9):536. doi: https://doi.org/10.1167/12.9.536.
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© ARVO (1962-2015); The Authors (2016-present)
Dyslexia is a prevalent reading disorder. The magnocellular hypothesis of dyslexia suggests that deficits in the magnocellular processing stream may account for some of the symptoms of the disorder. Reductions in the size of the magnocellular neurons in the human lateral geniculate nucleus (LGN) have been reported in a post-mortem study; however, the LGN has not been measured directly in living humans with dyslexia. We sought to measure the volume of the LGN in subjects with dyslexia compared to IQ-matched controls.
Thirteen dyslexics with measured behavioral deficits and 13 IQ-matched controls were scanned with a Siemens Trio 3T MRI scanner at the Brain Imaging Center at the University of Missouri. For each subject, 40 proton density weighted images were acquired (scanning time of one hour) with a resolution of 0.75x0.75x1 mm3. The images were interpolated to twice the resolution in each dimension then registered and averaged.The LGN were traced manually on these mean images by three independent observers who were blind to the subject’s group memberships. Finally the volume between the LGN of each subject with dyslexia and the corresponding control were compared.
The left LGN volume in subjects with dyslexia was significantly smaller than in the matched controls, approximately 20% smaller. Interestingly, no significant difference was found in the right LGN.
We have obtained measurments that are consistent with the magnocellular hypothesis of dyslexia. However, it is still unclear whether the volume reduction in the LGN of the subjects with dyslexia is restructed to the magnocellular layers or not.
Meeting abstract presented at VSS 2012
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