Effective brain connectivity explains causal interactions between the cerebellum and visual areas during a visual-attentive task in developmental dyslexia and typical readers

Developmental dyslexia (DD) is a neurodevelopmental disorder marked by persistent reading difficulties. While previous neuroimaging studies have revealed alterations in the functional connectivity of the ventral attention network (VAN) and cerebellum in DD, the effective brain connectivity of those networks remains understudied in DD. Dynamic Causal Modelling (DCM), a Bayesian framework, can estimate the direct causal influences (effective connectivity) and the hierarchical organization of activations in different brain regions. Here, for the first time, DCM was employed on functional magnetic resonance imaging (fMRI) data obtained by visual-attentive tasks to investigate effective connectivity within the cortico-cerebellar visual attention network in typical readers (TR) and individuals with DD. To assess attention networks, twenty participants of TR and twenty participants of DD underwent fMRI while performing full-field sinusoidal grating and coherent motion sensitivity tasks. The investigated visual attention network included: left and right Crus I of the Cerebellum, left and right middle frontal gyrus, left and right middle visual temporal area, and bilateral primary visual cortex. Four different DCM models were specified and estimated to study effective connectivity patterns in two groups. Group-level analysis used Random Effect Bayesian Model Selection to compare multiple DCM models, aiming to find the best explanation for the neuroimaging data and select the best-fitting model for each group. Results revealed differential effective connectivity patterns between the two groups, indicating altered organization of the VAN and cerebellar involvement in DD. Specifically, while the TR group exhibited right-lateralized VAN connectivity, the DD group displayed compensatory connectivity patterns. The present study contributes to our understanding of the neural mechanisms underlying developmental dyslexia and highlights the importance of investigating effective brain connectivity in neurodevelopmental disorders to open new insights for diagnostic and therapeutic approaches. Keywords: Developmental dyslexia, Dynamical Causal Modeling (DCM), functional magnetic resonance imaging (fMRI), cerebellum, ventral attention network