Are there shared neural correlates between dyslexia and ADHD? A meta-analysis of voxel-based morphometry studies

Abstract

BackgroundDyslexia and Attention-deficit/hyperactivity disorder (ADHD) are highly comorbid neurodevelopmental disorders (estimates of 25–40% bidirectional comorbidity). Previous work has identified strong genetic and cognitive overlap between the disorders, but neural overlap is relatively unexplored. This study is a systematic meta-analysis of existing voxel-based morphometry studies to determine whether there is any overlap in the gray matter correlates of both disorders.MethodsWe conducted anatomic likelihood estimate (ALE) meta-analyses of voxel-based morphometry studies in which individuals with dyslexia (15 studies; 417 cases, 416 controls) or ADHD (22 studies; 898 cases, 763 controls) were compared to typically developing controls. We generated ALE maps for dyslexia vs. controls and ADHD vs. controls using more conservative (p < .001, k = 50) and more lenient (p < .005, k = 50) thresholds. To determine the overlap of gray matter correlates of dyslexia and ADHD, we examined the statistical conjunction between the ALE maps for dyslexia vs. controls and ADHD vs. controls (false discovery rate [FDR] p < .05, k = 50, 5000 permutations).ResultsResults showed largely distinct gray matter differences associated with dyslexia and ADHD. There was no evidence of statistically significant gray matter overlap at our conservative threshold, and only one region of overlap in the right caudate at our more lenient threshold. Reduced gray matter in the right caudate may be relevant to shared cognitive correlates in executive functioning and/or procedural learning. The more general finding of largely distinct regional differences in gray matter between dyslexia and ADHD suggests that other neuroimaging modalities may be more sensitive to overlapping neural correlates, and that current neuroimaging recruitment approaches may be hindering progress toward uncovering neural systems associated with comorbidity.ConclusionsThe current study is the first to meta-analyze overlap between gray matter differences in dyslexia and ADHD, which is a critical step toward constructing a multi-level understanding of this comorbidity that spans the genetic, neural, and cognitive levels of analysis.

Comparative meta-analyses of brain structural and functional abnormalities during cognitive control in attention-deficit/hyperactivity disorder and autism spectrum disorder

“…2018), and supports the hypothesis of distinctive reward processing in ASD and ADHD (Kohls et al, 2014; van Dongen et al, 2015). Reduced vmOFC GMV in ADHD compared to TD controls extends relatively recent meta-analytic findings (McGrath & Stoodley, 2019; Norman et al, 2016), and there have been correlational reports between OFC GMV reduction and increased ADHD symptoms in large-scale general population studies (Albaugh et al, 2017; Fuentes et al, 2012; Korponay et al, 2017). Interestingly, our age-stratified results suggest that the ADHD-differentiating deficit features more consistently in adulthood, when co-occurring addiction behavioral problems increase (e.g.…”

Convergent and divergent structural and functional brain abnormalities associated with developmental dyslexia: a cross-linguistic meta-analysis of neuroimaging studies

“…Across writing systems, convergent structural and functional deficits were found around the left perisylvian region (i.e., left IFG, left supramarginal gyrus and left STG) due to reduced GMV and brain activation. The left perisylvian region is a very important component in the language network, which shows structural and functional abnormality in individuals with DD as suggested in previous metaanalysis studies (Linkersdorfer et al, 2012;Maisog et al, 2008;McGrath & Stoodley, 2019;Paulesu et al, 2014;Richlan et al, 2013). The left STG and the dorsal IFG are two core regions in the language model proposed by Friederici (2012), and by Hickok and Poeppel (2007).…”

“…In a meta-analysis, Linkersdorfer et al (2012) gathered nine voxelbased morphometry (VBM) studies in alphabetic languages and found consistent grey matter reduction in the left OT area and TP area, but failed to find reliable evidence in the left IFG. In another two meta-analysis studies in alphabetic languages, researchers only found consistent grey matter reduction in the left TP area but failed to find reduction in the OT area (McGrath & Stoodley, 2019;Richlan et al, 2013). These three meta-analytic studies echo findings from functional studies by showing abnormal brain structures within the classic reading network.…”

Pursuit eye movements in dyslexic children: evidence for an immaturity of brain oculomotor structures?

“…Note that, as reported by Capano, Minden, Chen, Schachar & Ickowicz ( 43 ) the association between dyslexia and ADHD is high given that about 26% of ADHD had a comorbid reading disability. More recently, McGrath and Stoodley ( 44 ) in a meta-analysis reported an overlap of gray matter between dyslexia and ADHD in the right caudate that is related to share cognitive activities for executive functions and/or procedural learning. Consequently in the present study any hyperactivity deficit was excluded using the ADHD Rating Scale-parental report (ADHD-RS) ( 45 ).…”