Neuroanatomic differences between dyslexic and normal readers on magnetic resonance imaging scans.

The areas of six bilateral brain segments in the right and left hemispheres, on a horizontal brain section, and the area of subdivisions of the corpus callosum, on a midsagittal brain section, were measured on magnetic resonance images obtained from 21 dyslexic and 29 control subjects. In the entire group, the frontal half of the horizontal brain section showed asymmetry, with the right side being larger, whereas posteriorly only the occipital polar segment was asymmetrical, with the left side being larger. Dyslexic subjects exhibited asymmetry, with the right side greater than the left side, in contrast to the relatively symmetrical pattern that is normally observed in the midposterior segment that corresponds to the angular gyrus. In the corpus callosum, dyslexic subjects were found to have a larger splenium than nondyslexic subjects, and dyslexic female subjects were found to have a larger splenium than dyslexic male subjects. Because transcallosal pathways connecting the left and right angular gyrus regions traverse through the splenium of the corpus callosum, the above findings in dyslexic subjects suggest an anatomic abnormality in the angular gyrus region.

[1]  G. Hynd,et al.  Dyslexia and brain morphology. , 1989, Psychological bulletin.

[2]  M. Gazzaniga,et al.  Magnetic resonance imaging morphology of the corpus callosum in monozygotic twins , 1989, Annals of neurology.

[3]  G. McCloskey.  Wide Range Achievement Test-Revised , 1987 .

[4]  William Byne,et al.  Can the corpus callosum predict gender, age, handedness, or cognitive differences? , 1986, Trends in Neurosciences.

[5]  J. Rumsey,et al.  Magnetic resonance imaging of brain anatomy in severe developmental dyslexia. , 1986, Archives of neurology.

[6]  J. Saver,et al.  Quantitative analysis of cerebral asymmetries. Fronto-occipital correlation, sexual dimorphism and association with handedness. , 1986, Archives of neurology.

[7]  E. Ross,et al.  Topography of the Human Corpus Callosum , 1985, Journal of neuropathology and experimental neurology.

[8]  S. F. Witelson.  The brain connection: the corpus callosum is larger in left-handers. , 1985, Science.

[9]  N. Geschwind,et al.  Developmental dyslexia: Four consecutive patients with cortical anomalies , 1985, Annals of neurology.

[10]  N. Geschwind,et al.  Cerebral lateralization. Biological mechanisms, associations, and pathology: I. A hypothesis and a program for research. , 1985, Archives of neurology.

[11]  A. Galaburda,et al.  Inferior parietal lobule. Divergent architectonic asymmetries in the human brain. , 1984, Archives of neurology.

[12]  K. Gross-Glenn,et al.  Evidence for deficit in interhemispheric transfer of information in dyslexic boys. , 1984, The International journal of neuroscience.

[13]  M. Naeser,et al.  CT criteria of hemisphere asymmetry fail to predict language laterality , 1984, Neurology.

[14]  M. Naeser.  Relationship Between Hemispheric Asymmetries on Computed Tomography Scan and Recovery from Aphasia , 1984 .

[15]  M. Naeser,et al.  Computed tomographic scan cerebral asymmetries and morphologic brain asymmetries. Correlation in the same cases post mortem. , 1984, Archives of neurology.

[16]  A. Damasio,et al.  The anatomic basis of pure alexia , 1983, Neurology.

[17]  R. Holloway,,et al.  Sexual dimorphism in the human corpus callosum. , 1982, Science.

[18]  A M Galaburda,et al.  Symmetry and asymmetry in the human posterior thalamus. I. Cytoarchitectonic analysis in normal persons. , 1982, Archives of neurology.

[19]  D. Weinberger,et al.  Asymmetrical volumes of the right and left frontal and occipital regions of the human brain , 1982, Annals of neurology.

[20]  A. Rademaker,et al.  Cerebral asymmetry in developmental dyslexia. , 1981, Archives of neurology.

[21]  A. Damasio,et al.  Human cerebral asymmetries evaluated by computed tomography. , 1980, Journal of neurology, neurosurgery, and psychiatry.

[22]  Daniel B Hier,et al.  Cerebral asymmetry and verbal intellectual deficits , 1980, Annals of neurology.

[23]  A. Galaburda,et al.  Cytoarchitectonic organization of the human auditory cortex , 1980, The Journal of comparative neurology.

[24]  C. Drake,et al.  Duration thresholds for letter identification in left and right visual fields for normal and reading-disabled children , 1978, Neuropsychologia.

[25]  D. Kido,et al.  Asymmetries of the cerebral hemispheres on computed tomograms. , 1978, Journal of computer assisted tomography.

[26]  Daniel B Hier,et al.  Developmental Dyslexia: Evidence for a Subgroup With a Reversal of Cerebral Asymmetry , 1978 .

[27]  D. Benson.  The third alexia. , 1977, Archives of neurology.

[28]  J. Guthrie,et al.  The genetics of specific reading disability , 1976, Annals of human genetics.

[29]  J A Wada,et al.  Cerebral hemispheric asymmetry in humans. Cortical speech zones in 100 adults and 100 infant brains. , 1975, Archives of neurology.

[30]  N. Geschwind.  The Anatomy of Acquired Disorders of Reading , 1974 .

[31]  N. Geschwind,et al.  Cerebral dominance and anatomic asymmetry. , 1972, The New England journal of medicine.

[32]  R. C. Oldfield.  The assessment and analysis of handedness: the Edinburgh inventory. , 1971, Neuropsychologia.

[33]  A. C. Eycleshymer,et al.  A cross-section anatomy , 1970 .

[34]  N. Geschwind,et al.  Human Brain: Left-Right Asymmetries in Temporal Speech Region , 1968, Science.