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Planum temporale, planum parietale and dichotic listening in dyslexia

Planum temporale, planum parietale and dichotic listening in dyslexia
Planum temporale, planum parietale and dichotic listening in dyslexia
A reduction or reversal of the normal leftward asymmetry of the planum temporale (PT) has been claimed to be typical of dyslexia, although some recent studies have challenged this view. In a population-based study of 20 right-handed dyslexic boys and 20 matched controls, we have measured the PT and the adjacent planum parietale (PP) region in sagittal magnetic resonance images. For the PT, mean left and right areas and asymmetry coefficients were compared. Since a PP area often could not be identified in one or both hemispheres, a qualitative comparison was used for this region. The total planar area (sum of PT and PP) was also compared between the two groups. A dichotic listening (DL) test with consonant–vowel syllables was administered to assess functional asymmetry of language. The results showed a mean leftward PT asymmetry in both the dyslexic and the control group, with no significant difference for the degree of PT asymmetry. Planned comparisons revealed however, a trend towards smaller left PT in the dyslexic group. In control children, but not in the dyslexic children, a significant correlation between PT asymmetry and reading was observed. A mean leftward asymmetry was also found for the total planar area, with no difference between the groups for the degree of asymmetry. Significantly fewer dyslexic children than control children showed a rightward asymmetry for the PP region. Both groups showed a normal right ear advantage on the DL task, with no significant difference for DL asymmetry. No significant correlation was observed between PT asymmetry and DL asymmetry. The present population-based study adds to recent reports of normal PT asymmetry in dyslexia, but indicates that subtle morphological abnormalities in the left planar area may be present in this condition.
reading disability, laterality, cerebral asymmetry, cerebral cortex
0028-3932
1704-1713
Heiervang, Einar
370be21c-ec4d-4938-b7ce-ec83501fde65
Hugdahl, Kenneth
8d44c66a-2b64-48e4-88f0-127686941416
Steinmetz, Helmuth
c6c44d22-1a90-4e6b-b9d0-58349c32e6e4
Smievoll, Alf Inge
d3352475-ac1d-48a6-9039-ff9492318eb7
Stevenson, Jim
0c85d29b-d294-43cb-ab8d-75e4737478e1
Lund, Anders
529b9d0a-5545-4516-bfd0-2e2a41d29183
Ersland, Lars
21ce6267-eeb5-4ed6-8009-bbb53b3ea761
Lundervold, Arvid
b06023d1-a85a-4021-a72a-81309d76c32d
Heiervang, Einar
370be21c-ec4d-4938-b7ce-ec83501fde65
Hugdahl, Kenneth
8d44c66a-2b64-48e4-88f0-127686941416
Steinmetz, Helmuth
c6c44d22-1a90-4e6b-b9d0-58349c32e6e4
Smievoll, Alf Inge
d3352475-ac1d-48a6-9039-ff9492318eb7
Stevenson, Jim
0c85d29b-d294-43cb-ab8d-75e4737478e1
Lund, Anders
529b9d0a-5545-4516-bfd0-2e2a41d29183
Ersland, Lars
21ce6267-eeb5-4ed6-8009-bbb53b3ea761
Lundervold, Arvid
b06023d1-a85a-4021-a72a-81309d76c32d

Heiervang, Einar, Hugdahl, Kenneth, Steinmetz, Helmuth, Smievoll, Alf Inge, Stevenson, Jim, Lund, Anders, Ersland, Lars and Lundervold, Arvid (2000) Planum temporale, planum parietale and dichotic listening in dyslexia. Neuropsychologia, 38 (13), 1704-1713. (doi:10.1016/S0028-3932(00)00085-3).

Record type: Article

Abstract

A reduction or reversal of the normal leftward asymmetry of the planum temporale (PT) has been claimed to be typical of dyslexia, although some recent studies have challenged this view. In a population-based study of 20 right-handed dyslexic boys and 20 matched controls, we have measured the PT and the adjacent planum parietale (PP) region in sagittal magnetic resonance images. For the PT, mean left and right areas and asymmetry coefficients were compared. Since a PP area often could not be identified in one or both hemispheres, a qualitative comparison was used for this region. The total planar area (sum of PT and PP) was also compared between the two groups. A dichotic listening (DL) test with consonant–vowel syllables was administered to assess functional asymmetry of language. The results showed a mean leftward PT asymmetry in both the dyslexic and the control group, with no significant difference for the degree of PT asymmetry. Planned comparisons revealed however, a trend towards smaller left PT in the dyslexic group. In control children, but not in the dyslexic children, a significant correlation between PT asymmetry and reading was observed. A mean leftward asymmetry was also found for the total planar area, with no difference between the groups for the degree of asymmetry. Significantly fewer dyslexic children than control children showed a rightward asymmetry for the PP region. Both groups showed a normal right ear advantage on the DL task, with no significant difference for DL asymmetry. No significant correlation was observed between PT asymmetry and DL asymmetry. The present population-based study adds to recent reports of normal PT asymmetry in dyslexia, but indicates that subtle morphological abnormalities in the left planar area may be present in this condition.

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Published date: 2000
Keywords: reading disability, laterality, cerebral asymmetry, cerebral cortex

Identifiers

Local EPrints ID: 18374
URI: https://eprints.soton.ac.uk/id/eprint/18374
ISSN: 0028-3932
PURE UUID: 71ddfd26-1624-496e-92b4-5934a1dfecf1

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Date deposited: 06 Jan 2006
Last modified: 17 Jul 2017 16:36

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Contributors

Author: Einar Heiervang
Author: Kenneth Hugdahl
Author: Helmuth Steinmetz
Author: Alf Inge Smievoll
Author: Jim Stevenson
Author: Anders Lund
Author: Lars Ersland
Author: Arvid Lundervold

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