Structural white matter connectometry of reading and dyslexia

Aleksi J Sihvonen; Paula Virtala; Anja Thiede; Marja Laasonen; Teija Kujala

doi:10.1016/j.neuroimage.2021.118411

Structural white matter connectometry of reading and dyslexia

Neuroimage. 2021 Nov 1:241:118411. doi: 10.1016/j.neuroimage.2021.118411. Epub 2021 Jul 20.

Authors

Aleksi J Sihvonen¹, Paula Virtala², Anja Thiede², Marja Laasonen³, Teija Kujala²

Affiliations

¹ Cognitive Brain Research Unit, Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Finland; School of Health and Rehabilitation Sciences, Queensland Aphasia Research Centre and UQ Centre for Clinical Research, The University of Queensland, Australia. Electronic address: aleksi.sihvonen@helsinki.fi.
² Cognitive Brain Research Unit, Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Finland.
³ Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Finland; Department of Otorhinolaryngology and Phoniatrics, Head and Neck Surgery, Helsinki University Hospital and University of Helsinki, Finland; Logopedics, School of Humanities, Philosophical Faculty, University of Eastern Finland.

PMID: 34293464
DOI: 10.1016/j.neuroimage.2021.118411

Abstract

Current views on the neural network subserving reading and its deficits in dyslexia rely largely on evidence derived from functional neuroimaging studies. However, understanding the structural organization of reading and its aberrations in dyslexia requires a hodological approach, studies of which have not provided consistent findings. Here, we adopted a whole brain hodological approach and investigated relationships between structural white matter connectivity and reading skills and phonological processing in a cross-sectional study of 44 adults using individual local connectome matrix from diffusion MRI data. Moreover, we performed quantitative anisotropy aided differential tractography to uncover structural white matter anomalies in dyslexia (23 dyslexics and 21 matched controls) and their correlation to reading-related skills. The connectometry analyses indicated that reading skills and phonological processing were both associated with corpus callosum (tapetum), forceps major and minor, as well as cerebellum bilaterally. Furthermore, the left dorsal and right thalamic pathways were associated with phonological processing. Differential tractography analyses revealed structural white matter anomalies in dyslexics in the left ventral route and bilaterally in the dorsal route compared to the controls. Connectivity deficits were also observed in the corpus callosum, forceps major, vertical occipital fasciculus and corticostriatal and thalamic pathways. Altered structural connectivity in the observed differential tractography results correlated with poor reading skills and phonological processing. Using a hodological approach, the current study provides novel evidence for the extent of the reading-related connectome and its aberrations in dyslexia. The results conform current functional neuroanatomical models of reading and developmental dyslexia but provide novel network-level and tract-level evidence on structural connectivity anomalies in dyslexia, including the vertical occipital fasciculus.

Keywords: DTI; Dyslexia; Phonological processing; Reading; Structural connectometry.

Publication types

Observational Study
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Brain / diagnostic imaging
Brain / physiology
Connectome / methods*
Cross-Sectional Studies
Dyslexia / diagnostic imaging*
Dyslexia / physiopathology
Female
Humans
Magnetic Resonance Imaging / methods
Male
Nerve Net / diagnostic imaging*
Nerve Net / physiology
Reading*
White Matter / diagnostic imaging*
White Matter / physiology
Young Adult