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Anatomical risk factors for phonological dyslexia
C M Leonard1, M A Eckert, L J Lombardino
1Department of Neuroscience, University of Florida Brain Institute, Gainesville, FL 32611, USA. leonard@ufbi.ufl.edu
Cerebral Cortex (New York, N.Y. : 1991)
|February 24, 2001
Summary
Neuroimaging reveals distinct anatomical markers for phonological dyslexia, a reading disability subtype. These brain structure differences correlate with specific cognitive deficits, aiding in precise phenotype definition for genetic studies.
Area of Science:
- Neuroscience
- Behavioral Genetics
- Cognitive Psychology
Background:
- Behavioral genetic studies require precise definition of homogenous phenotypes.
- Reading disability (RD) is a complex phenotype with significant variability.
- Identifying neuroanatomical markers can help refine the RD phenotype.
Purpose of the Study:
- To identify anatomical brain markers associated with a specific reading disability phenotype.
- To investigate the relationship between neuroanatomical variations and cognitive deficits in reading disability.
- To provide neurobiological support for distinct RD subtypes.
Main Methods:
- Volumetric MRI scans were performed on 13 individuals with reading disability (9 with phonological dyslexia) and 15 controls.
- Subjects completed cognitive and reading assessments.
- Four specific anatomical measures were analyzed: cerebral asymmetry, cerebellar asymmetry, sylvian fissure asymmetry, and Heschl's gyrus duplication.
Main Results:
- Four anatomical measures differentiated phonological dyslexia (PD) from other subjects: rightward cerebral asymmetry, leftward cerebellar anterior lobe asymmetry, leftward sylvian fissure asymmetry, and left Heschl's gyrus duplication.
- A combined score of these four measures predicted phonological memory.
- Low total cerebral volume predicted oral and written comprehension skills.
Conclusions:
- Neuroanatomical findings support a distinct RD phenotype characterized by phonological deficits with normal or superior comprehension.
- Specific brain structural variations are linked to phonological processing deficits.
- Individual variation in cortical structure may bridge the gap between genotype and behavior in reading disability.
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