Dynamic brain state alterations during reading in children with dyslexia: A hidden semi-Markov model analysis

Dyslexia is the most common learning disorder and has been associated with alterations in functional connectivity between distributed brain regions. While prior research has primarily focused on static connectivity patterns, considerably less attention has been paid to the dynamic fluctuations of functional brain networks underlying reading processes. We applied a state-based dynamic functional connectivity (dFC) analysis to task-based fMRI data acquired during a reading-aloud task in children with dyslexia (n = 19) and typically developing (TD) children (n = 16). Hidden Semi-Markov Models (HSMMs) were used to identify recurring, model-defined network states and estimate individual state sequences. For each state, occupancy time, sojourn duration, and transition probabilities were computed and compared between groups. Children with dyslexia spent significantly less time in a low-integration brain state and more time in states characterised by stronger positive connectivity compared with TD children. The most highly integrated state was observed exclusively in the dyslexia group and accounted for a substantial proportion of scan time. In addition, dyslexia was associated with altered sojourn-duration distributions in two states, including prolonged durations in an intermediate state, and transition patterns biased toward increasingly integrated configurations, whereas TD children more frequently transitioned back to the low-integration state. These findings provide evidence that dyslexia is associated with altered dynamic functional connectivity within the sampled task-constrained attention-language system, characterised by altered engagement across a graded integration-segregation continuum and atypical temporal regulation of brain state transitions. Such alterations in network dynamics may reflect differences in the organisation of this task-relevant system associated with dyslexia, although their direct behavioural significance remains to be established.