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Morphological differences in the lateral geniculate nucleus associated with dyslexia.

Giraldo-Chica M, Hegarty JP, Schneider KA - Neuroimage Clin (2015)

Bottom Line: Developmental dyslexia is a common learning disability characterized by normal intelligence but difficulty in skills associated with reading, writing and spelling.We sought to test the basis of this theory by directly measuring the lateral geniculate nucleus (LGN), the only location in the brain where the magnocellular and parvocellular streams are spatially disjoint.The functional significance of this asymmetry is unknown, but these results are consistent with the magnocellular theory and support theories of dyslexia that involve differences in the early visual system.

View Article: PubMed Central - PubMed

Affiliation: Centre for Vision Research, York University, Toronto, Ontario M3J 1P3, Canada ; Department of Medicine, University of Barcelona, Barcelona, Catalonia, Spain.

ABSTRACT
Developmental dyslexia is a common learning disability characterized by normal intelligence but difficulty in skills associated with reading, writing and spelling. One of the most prominent, albeit controversial, theories of dyslexia is the magnocellular theory, which suggests that malfunction of the magnocellular system in the brain is responsible for the behavioral deficits. We sought to test the basis of this theory by directly measuring the lateral geniculate nucleus (LGN), the only location in the brain where the magnocellular and parvocellular streams are spatially disjoint. Using high-resolution proton-density weighted MRI scans, we precisely measured the anatomical boundaries of the LGN in 13 subjects with dyslexia (five female) and 13 controls (three female), all 22-26 years old. The left LGN was significantly smaller in volume in subjects with dyslexia and also differed in shape; no differences were observed in the right LGN. The functional significance of this asymmetry is unknown, but these results are consistent with the magnocellular theory and support theories of dyslexia that involve differences in the early visual system.

No MeSH data available.


Related in: MedlinePlus

Probability maps of the LGN anatomy in native space. Each row shows a separate coronal slice from the anterior LGN. In the inset, the slice locations are shaded green over a horizontal slice through the control LGN map. The slices are arranged from anterior (A) to posterior (P). The left two columns show the average map of all subjects in each group for the left (L) and right (R) LGN in the native space, registered by the center of mass. The color code indicates the probability of each voxel belonging to the LGN. The third column shows maps of the difference in probabilities between the dyslexia and control maps. The rightmost column indicates the statistical significance of the difference for the left LGN, corrected for multiple comparisons. There were no significant differences in the right LGN.
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f0015: Probability maps of the LGN anatomy in native space. Each row shows a separate coronal slice from the anterior LGN. In the inset, the slice locations are shaded green over a horizontal slice through the control LGN map. The slices are arranged from anterior (A) to posterior (P). The left two columns show the average map of all subjects in each group for the left (L) and right (R) LGN in the native space, registered by the center of mass. The color code indicates the probability of each voxel belonging to the LGN. The third column shows maps of the difference in probabilities between the dyslexia and control maps. The rightmost column indicates the statistical significance of the difference for the left LGN, corrected for multiple comparisons. There were no significant differences in the right LGN.

Mentions: The LGN masks in native space were registered to each other by aligning their centers of mass and averaging to assess LGN morphology independent of position within the brain (Fig. 3). In these coordinates, the morphology of the LGN varied significantly between groups. The voxels in the most anterior and posterior slices of the left LGN had a high probability of belonging to the control LGN, indicating the reduced depth of the LGN in the dyslexia group. This difference was less pronounced in the right LGN, where no voxels were significantly different between the group distributions.


Morphological differences in the lateral geniculate nucleus associated with dyslexia.

Giraldo-Chica M, Hegarty JP, Schneider KA - Neuroimage Clin (2015)

Probability maps of the LGN anatomy in native space. Each row shows a separate coronal slice from the anterior LGN. In the inset, the slice locations are shaded green over a horizontal slice through the control LGN map. The slices are arranged from anterior (A) to posterior (P). The left two columns show the average map of all subjects in each group for the left (L) and right (R) LGN in the native space, registered by the center of mass. The color code indicates the probability of each voxel belonging to the LGN. The third column shows maps of the difference in probabilities between the dyslexia and control maps. The rightmost column indicates the statistical significance of the difference for the left LGN, corrected for multiple comparisons. There were no significant differences in the right LGN.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4459050&req=5

f0015: Probability maps of the LGN anatomy in native space. Each row shows a separate coronal slice from the anterior LGN. In the inset, the slice locations are shaded green over a horizontal slice through the control LGN map. The slices are arranged from anterior (A) to posterior (P). The left two columns show the average map of all subjects in each group for the left (L) and right (R) LGN in the native space, registered by the center of mass. The color code indicates the probability of each voxel belonging to the LGN. The third column shows maps of the difference in probabilities between the dyslexia and control maps. The rightmost column indicates the statistical significance of the difference for the left LGN, corrected for multiple comparisons. There were no significant differences in the right LGN.
Mentions: The LGN masks in native space were registered to each other by aligning their centers of mass and averaging to assess LGN morphology independent of position within the brain (Fig. 3). In these coordinates, the morphology of the LGN varied significantly between groups. The voxels in the most anterior and posterior slices of the left LGN had a high probability of belonging to the control LGN, indicating the reduced depth of the LGN in the dyslexia group. This difference was less pronounced in the right LGN, where no voxels were significantly different between the group distributions.

Bottom Line: Developmental dyslexia is a common learning disability characterized by normal intelligence but difficulty in skills associated with reading, writing and spelling.We sought to test the basis of this theory by directly measuring the lateral geniculate nucleus (LGN), the only location in the brain where the magnocellular and parvocellular streams are spatially disjoint.The functional significance of this asymmetry is unknown, but these results are consistent with the magnocellular theory and support theories of dyslexia that involve differences in the early visual system.

View Article: PubMed Central - PubMed

Affiliation: Centre for Vision Research, York University, Toronto, Ontario M3J 1P3, Canada ; Department of Medicine, University of Barcelona, Barcelona, Catalonia, Spain.

ABSTRACT
Developmental dyslexia is a common learning disability characterized by normal intelligence but difficulty in skills associated with reading, writing and spelling. One of the most prominent, albeit controversial, theories of dyslexia is the magnocellular theory, which suggests that malfunction of the magnocellular system in the brain is responsible for the behavioral deficits. We sought to test the basis of this theory by directly measuring the lateral geniculate nucleus (LGN), the only location in the brain where the magnocellular and parvocellular streams are spatially disjoint. Using high-resolution proton-density weighted MRI scans, we precisely measured the anatomical boundaries of the LGN in 13 subjects with dyslexia (five female) and 13 controls (three female), all 22-26 years old. The left LGN was significantly smaller in volume in subjects with dyslexia and also differed in shape; no differences were observed in the right LGN. The functional significance of this asymmetry is unknown, but these results are consistent with the magnocellular theory and support theories of dyslexia that involve differences in the early visual system.

No MeSH data available.


Related in: MedlinePlus