A structural–functional basis for dyslexia in the cortex of Chinese readers

^†Department of Linguistics and
^‡State Key Laboratory of Brain and Cognitive Sciences, University of Hong Kong, Pokfulam Road, Hong Kong;
^§College of Computer Science and Technology, Beijing Institute of Technology, Beijing 100081, China;
^¶Beijing 306 Hospital, Beijing 100101, China; and
^‖Learning Research and Development Center, University of Pittsburgh, Pittsburgh, PA 15260

Communicated by Robert Desimone, Massachusetts Institute of Technology, Cambridge, MA, February 25, 2008 (received for review January 1, 2008)

Abstract

Developmental dyslexia is a neurobiologically based disorder that affects ≈5–17% of school children and is characterized by a severe impairment in reading skill acquisition. For readers of alphabetic (e.g., English) languages, recent neuroimaging studies have demonstrated that dyslexia is associated with weak reading-related activity in left temporoparietal and occipitotemporal regions, and this activity difference may reflect reductions in gray matter volume in these areas. Here, we find different structural and functional abnormalities in dyslexic readers of Chinese, a nonalphabetic language. Compared with normally developing controls, children with impaired reading in logographic Chinese exhibited reduced gray matter volume in a left middle frontal gyrus region previously shown to be important for Chinese reading and writing. Using functional MRI to study language-related activation of cortical regions in dyslexics, we found reduced activation in this same left middle frontal gyrus region in Chinese dyslexics versus controls, and there was a significant correlation between gray matter volume and activation in the language task in this same area. By contrast, Chinese dyslexics did not show functional or structural (i.e., volumetric gray matter) differences from normal subjects in the more posterior brain systems that have been shown to be abnormal in alphabetic-language dyslexics. The results suggest that the structural and functional basis for dyslexia varies between alphabetic and nonalphabetic languages.

Footnotes

^††To whom correspondence should be addressed. E-mail: tanlh{at}hku.hk
Author contributions: W.T.S., C.A.P., and L.H.T. designed research; W.T.S., Z.J., and L.H.T. performed research; W.T.S., N.Z., and L.H.T. analyzed data; and W.T.S., C.A.P., and L.H.T. wrote the paper.
The authors declare no conflict of interest.