[Abstract Title]. - Society for Neuroscience

Title: The neurobiological profile of adult disabled readers supports the phonological deficit
hypothesis of dyslexia
Authors: A. ZUMBERGE 1 , J. L. BRUNO 2 , J. G. GOLDMAN 2 , *C.-P. KO 1 , Z.-L. LU 2 , F. R.
MANIS 2 ;
1 Dept Biol. Sci., 2 Dept Psychology, USC, Los Angeles, CA
Abstract: The cognitive profile of reading disability is marked by phonological deficits. The
neurobiological profile that has emerged recently includes decreased activity in posterior brain
regions such as the superior temporal gyrus (STG; which is associated with phonological access),
and particularly the occipitotemporal region (OT; which is associated with orthographic
processing). Researchers have interpreted increased activity in more anterior regions (inferior
frontal gyrus; IFG) as compensation for deficits in orthographic and phonological processing.
The present study aimed to replicate previous fMRI findings of reduced OT activation and
elevated IFG activation in lower skilled adult readers. Regions of interest were localized on an
individual basis using a separate block-design rhyming task, and BOLD responses within these
regions during an event-related phonological lexical decision task were compared across skill
groups and correlated with cognitive measures of reading and phonological skill. Surprisingly,
no significant differences in activation pattern were found in OT, suggesting that dysfunction in
OT is not always present in individuals with reading disability. In STG and IFG, the reading
disabled group displayed deficits in phonological sensitivity; activation by phonologically
familiar pseudohomophones was equivalent to that by phonologically unfamiliar pseudowords.
Correlations between activation level and language skills were positive in STG and negative in
IFG. These observations in regions commonly associated with phonological processing may
account for the inefficient decoding and slow access to phonological representations observed in
numerous behavioral studies. They suggest that, at least in adults functioning at the college level,
persistent reading difficulties are related to deficits at the phonological, rather than orthographic,
level. This lends neural support to the behaviorally-based phonological hypothesis for dyslexia.
Disclosures: A. Zumberge, None; C. Ko , None; J.L. Bruno, None; J.G. Goldman, None; Z.
Lu, None; F.R. Manis, None.
Poster
249. Dyslexia, SLI, and Other Disorders of Cognition and Behavior
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 249.24/V9
Topic: F.01.d. Language
Support: NIDCD Intramural Research Program