Authors: Cyril Pernet, Jesper Andersson, Eraldo Paulesu, Jean Francois Demonet.

Article: When all hypotheses are right: a multifocal account of dyslexia..

Publication: Human Brain Mapping (Wiley). 30(7), 2278–2292 2009 | DOI: 10.1002/hbm.20670

[Full Text] [PubMed]


Many hypotheses have been proposed about the brain underpinnings of developmental dyslexia, but none of them accommodates the variable deficits observed. To address the issue of anatomical deficits in dyslexia; total and partial volumes, lateralization indices (LI), and local gray matter volumes (LGMV) were measured. Analyses were performed in large samples of control and dyslexic subjects, and in correlation with their performance on phonological, reading, and spelling tests. Results indicate an absence of net differences in terms of volumes but significant continuities and discontinuities between groups in their correlations between LI, LGMV, and performances. Structural connectivity also highlighted correlations between areas showing (dis)continuities between control and dyslexic subjects. Overall, our data put forward the idea of a multifocal brain abnormalities in dyslexia with a major implication of the left superior temporal gyrus, occipital-temporal cortices, and lateral/medial cerebellum, which could account for the diverse deficits predicted by the different theories.

Tagged as: fMRI and neural connectivity


Pernet, C., Andersson, J., Paulesu, E., & Demonet, J. F. (2009). When all hypotheses are right: a multifocal account of dyslexia. Human brain mapping, 30(7), 2278–2292.

Excerpts from Full Text / Notes:
Almost all sites proposed to be involved in dyslexia by the different theories were observed in this work on LGMV. Previous studies typically did not report all expected involved sites possibly because of too small group sizes, biasing the statistics, and/or because performances in the different components of reading (visual, phonological, lexical, spelling skills) were not all controlled. Here, using sufficiently large sample and correlating gray matter volumes with reading-related skills, we observed differences mainly around the left IFG, the left STG, the fusiform gyri and the lateral superior, and inferior medial cerebellum. These findings lend support to a multifocal
explanation of behavioral deficits observed in dyslexia. However, the total absence of correlation with the phonological deletion task over the whole brain and with the pseudo-word reading task over the cerebrum in dyslexic subjects suggest that brain areas involved in or related to phonological processing (STG, IFG, and possibly left fusiform)are primarily altered in dyslexia.

Leave a public question or comment:

If you need personal help or assistance please use our contact forms instead.

All comments are moderated. Comments that are not relevant to the page topic or which contain identifiable personal information will be removed.

Your email address will not be published. Required fields are marked *