Authors: S. Brem, U. Maurer, M. Kronbichler, M. Schurz, F. Richlan, V. Blau, J. Reithler, S. van der Mark, E. Schulz, K. Bucher, K. Moll, K. Landerl, E. Martin, R. Goebel, G. Schulte-Körne, L. Blomert, H. Wimmer & D. Brandeis.
Publication: Scientific Reports (Nature.com). 10, Article number: 18728 2020 | DOI: 10.1038/s41598-020-75111-8
The visual word form area (VWFA) in the left ventral occipito-temporal (vOT) cortex is key to fluent reading in children and adults. Diminished VWFA activation during print processing tasks is a common finding in subjects with severe reading problems. Here, we report fMRI data from a multicentre study with 140 children in primary school (7.9–12.2 years; 55 children with dyslexia, 73 typical readers, 12 intermediate readers). All performed a semantic task on visually presented words and a matched control task on symbol strings. With this large group of children, including the entire spectrum from severely impaired to highly fluent readers, we aimed to clarify the association of reading fluency and left vOT activation during visual word processing. The results of this study confirm reduced word-sensitive activation within the left vOT in children with dyslexia. Interestingly, the association of reading skills and left vOT activation was especially strong and spatially extended in children with dyslexia. Thus, deficits in basic visual word form processing increase with the severity of reading disability but seem only weakly associated with fluency within the typical reading range suggesting a linear dependence of reading scores with VFWA activation only in the poorest readers.
Brem, S., Maurer, U., Kronbichler, M. et al. Visual word form processing deficits driven by severity of reading impairments in children with developmental dyslexia. Sci Rep 10, 18728 (2020). https://doi.org/10.1038/s41598-020-75111-8
While phonological deficits have been suggested to play a central role for the impairments seen in dyslexia, processing visual words for meaning remains the central task in reading. Thus, understanding how poor readers and especially children with dyslexia process visual words in the context of a semantic task is essential, and functional neuroimaging studies offer insight into the neural mechanisms involved.
Taken together, this large-scale neuroimaging study on the influence of word reading fluency on brain activation emphasizes the important role of the left vOT for reading skills and highlights its functional impairment in poor reading children. It extends the insight of previous large-scale studies specifically challenging phonological processing and using more liberal criteria for defining dyslexia by focussing on reading for meaning. Thus, the present study represents one of the largest datasets (n = 140) on functional activation in children with severe dyslexia compared to typical readers and clearly corroborates previous notions that the print-sensitive activation in the left vOT represents a critical limiting factor of reading for meaning especially at the lower end of the reading fluency spectrum.