Grey Matter Alterations Co-Localize with Functional Abnormalities in Developmental Dyslexia: An ALE Meta-Analysis

Abstract

The neural correlates of developmental dyslexia have been investigated intensively over the last two decades and reliable evidence for a dysfunction of left-hemispheric reading systems in dyslexic readers has been found in functional neuroimaging studies. In addition, structural imaging studies using voxel-based morphometry (VBM) demonstrated grey matter reductions in dyslexics in several brain regions. To objectively assess the consistency of these findings, we performed activation likelihood estimation (ALE) meta-analysis on nine published VBM studies reporting 62 foci of grey matter reduction in dyslexic readers. We found six significant clusters of convergence in bilateral temporo-parietal and left occipito-temporal cortical regions and in the cerebellum bilaterally. To identify possible overlaps between structural and functional deviations in dyslexic readers, we conducted additional ALE meta-analyses of imaging studies reporting functional underactivations (125 foci from 24 studies) or overactivations (95 foci from 11 studies ) in dyslexics. Subsequent conjunction analyses revealed overlaps between the results of the VBM meta-analysis and the meta-analysis of functional underactivations in the fusiform and supramarginal gyri of the left hemisphere. An overlap between VBM results and the meta-analysis of functional overactivations was found in the left cerebellum. The results of our study provide evidence for consistent grey matter variations bilaterally in the dyslexic brain and substantial overlap of these structural variations with functional abnormalities in left hemispheric regions.

CNVs conferring risk of autism or schizophrenia affect cognition in controls

“…In dyslexia, grey matter abnormalities in the supramarginal gyrus were prominent in a recent meta-analysis 29 . Grey matter reductions in a very similar location in pACC have also been seen in developmental dyscalculia 30 .…”

Individual Differences in Adult Reading Are Associated with Left Temporo-parietal to Dorsal Striatal Functional Connectivity

“…Phonological processing relies heavily on left hemisphere temporo-parietal language and auditory regions (Vigneau et al 2006). Meta-analyses of reading-relevant functional and neuroanatomical correlates of RD (Maisog et al 2008;Richlan et al 2009Richlan et al , 2011Richlan et al , 2013Linkersdörfer et al 2012), as well as studies of interindividual variability in reading competence (Koyama et al 2011), highlight the role of regions including the temporo-parietal junction (TPJ).…”

Visuo-Spatial Skills in Atypical Readers

“…The disease model of RD has, understandably, dominated the neurobiological studies, and researchers have tended to focus on the left hemisphere languagebased systems or the classic reading circuit: left hemisphere inferior frontal, inferior temporo-occipital, and temporo-parietal areas (Linkersdörfer, Lonnemann, Lindberg, Hasselhorn, & Fiebach, 2012;Richlan et al, 2009Richlan et al, , 2011Vandermosten, Hoeft, & Norton, 2016). Research, however, shows that individuals with RD often have broader differences in brain functions and structures not limited to the left hemisphere, with behavioral consequences we do not fully understand (Diehl et al, 2014;Eckert, 2004;Gilger & Hynd, 2008;Hynd, Semrud-Clikeman, Lorys, Novey, & Eliopulos, 1990;Galaburda, LoTurco Ramus, Fitch, & Rosen, 2006;Gilger & Kaplan, 2001;Linkersdörfer et al, 2012;Maisog, Einbinder, Flowers, Turkeltaub, & Eden, 2008;Olulade, Gilger, Talavage, Hynd, & McAteer, 2012;Richlan et al, 2009Richlan et al, , 2011.…”

“…Research, however, shows that individuals with RD often have broader differences in brain functions and structures not limited to the left hemisphere, with behavioral consequences we do not fully understand (Diehl et al, 2014;Eckert, 2004;Gilger & Hynd, 2008;Hynd, Semrud-Clikeman, Lorys, Novey, & Eliopulos, 1990;Galaburda, LoTurco Ramus, Fitch, & Rosen, 2006;Gilger & Kaplan, 2001;Linkersdörfer et al, 2012;Maisog, Einbinder, Flowers, Turkeltaub, & Eden, 2008;Olulade, Gilger, Talavage, Hynd, & McAteer, 2012;Richlan et al, 2009Richlan et al, , 2011. In addition to the reading pathway of the left hemisphere, the brains of people with RD show structural and/ or functional differences in the right hemisphere, subcortical and cerebellar regions (Eckert, 2004;Gilger & Kaplan, 2001;Galaburda et al, 2006;Galaburda, 1992;Hynd et al, 1990;Lindell, 2006;Linkersdörfer et al, 2012;Maisog et al, 2008;Pugh et al, 2000;Richlan et al, 2009Richlan et al, , 2011Temple et al, 2003). While the processing of languagerelated information is not constrained to the left hemisphere, these other regions where RD differences have been found are known to be important for other functions as well, such as processing visuo-spatial information, social, affective, and musical information.…”