Authors: Shaywitz, B.A., Skudlarski, P., Holahan, J.M., Marchione, K.E., Constable, R.T., Fulbright, R.K., Zelterman, D., Lacadie, C. and Shaywitz, S.E..
Publication: Annals of Neurology (Wiley). 61: 363-370 2017 | DOI: 10.1002/ana.21093
To examine age‐related changes in the neural systems for reading in nonimpaired and dyslexic children and adolescents.
Functional magnetic resonance imaging was used to study age‐related changes in the neural systems for reading in a cross‐sectional sample of 232 right‐handed children 7 to 18 years of age (113 dyslexic readers and 119 nonimpaired readers) as they read pseudowords.
In nonimpaired readers, systems in the left anterior lateral occipitotemporal area developed with age, whereas systems in the right superior and middle frontal regions decreased. In contrast, in dyslexic readers, systems in the left posterior medial occipitotemporal regions developed with age. Older nonimpaired readers were left lateralized in the anterior lateral occipitotemporal area; there was no difference in asymmetry between younger and older dyslexic readers.
These findings offer a possible neurobiological explanation for the differences in reading acquisition between dyslexic and nonimpaired readers and provide further evidence of the critical role of the left occipitotemporal region in the development of reading.
These findings indicate that systems for reading that develop with age in dyslexic readers differ from those in nonimpaired readers, primarily in being localized to a more posterior and medial region, rather than a more anterior and lateral occipitotemporal region. Interestingly, this difference in activation patterns between the two groups of readers has parallels to reported brain activation differences observed during reading of two Japanese writing systems: Kana and Kanji.
In contrast, posterior medial occipitotemporal activation, comparable with that observed in dyslexic readers, was noted during reading of Kanji script. Consideration of the mechanisms used for reading Kanji compared with Kana provide insights into potentially different mechanisms that develop with age in dyslexic contrasted with nonimpaired readers. Kanji script uses ideographs where each character must be memorized, suggesting that the posterior medial occipitotemporal region functions as part of a memory-based system. We suppose that as dyslexic children mature, this posterior medial system supports memorization rather than the progressive sound–symbol linkages observed in nonimpaired readers. And evidence exists that dyslexic readers are not able to make good use of sound–symbol linkages as they mature; instead, they come to rely on
Our findings also indicate that it is a single reading system that develops with age: for nonimpaired readers it is the anterior lateral, and for dyslexic readers it is the posterior medial occipitotemporal region. Such findings are in agreement with a report indicating that, over time, literacy can best be modeled as a single unitary construct rather than as multiple, separate, components of reading (eg, phonological awareness, word reading, passage comprehension).
Citation: Shaywitz, B.A., Skudlarski, P., Holahan, J.M., Marchione, K.E., Constable, R.T., Fulbright, R.K., Zelterman, D., Lacadie, C. and Shaywitz, S.E. (2007), Age‐related changes in reading systems of dyslexic children. Ann Neurol., 61: 363-370. doi:10.1002/ana.21093