Graph Analysis of EEG Functional Connectivity Networks During a Letter-Speech Sound Binding Task in Adult Dyslexics

Abstract

We performed an EEG graph analysis on data from 31 typical readers (22.27 ± 2.53 y/o) and 24 dyslexics (22.99 ± 2.29 y/o), recorded while they were engaged in an audiovisual task and during resting-state. The task simulates reading acquisition as participants learned new letter-sound mappings via feedback. EEG data was filtered for the delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), and beta (13–30 Hz) bands. We computed the Phase Lag Index (PLI) to provide an estimate of the functional connectivity between all pairs of electrodes per band. Then, networks were constructed using a Minimum Spanning Tree (MST), a unique sub-graph connecting all nodes (electrodes) without loops, aimed at minimizing bias in between groups and conditions comparisons. Both groups showed a comparable accuracy increase during task blocks, indicating that they correctly learned the new associations. The EEG results revealed lower task-specific theta connectivity, and lower theta degree correlation over both rest and task recordings, indicating less network integration in dyslexics compared to typical readers. This pattern suggests a role of theta oscillations in dyslexia and may reflect differences in task engagement between the groups, although robust correlations between MST metrics and performance indices were lacking.

Neural representation of association strength and prediction error during novel symbol-speech sounds learning

“…Two previous EEG studies used a similar learning task to examine differences between typical and dyslexic adult readers in physiological responses to feedback 25 and in oscillatory networks 26 . Their findings suggested differences between typical and impaired readers that would require further specification both in terms of brain networks and cognitive processes involved.…”

Brain Source Correlates of Speech Perception and Reading Processes in Children With and Without Reading Difficulties

“…However, the nature of the link between the two modalities remains unclear (Gibson et al, 2006 ; Wright and Conlon, 2009 ; Blau et al, 2010 ; Georgiou et al, 2012 ; Ye et al, 2017 ; Rüsseler et al, 2018 ; Stein, 2018 ). Several studies have investigated this relationship using simultaneous auditory and visual stimuli in dyslexic vs. typical readers using behavioral and brain measures (Aravena et al, 2018 ; Karipidis et al, 2018 ; Fraga-González et al, 2021 ). In the present study, we investigated the extent to which speech processing at the brain level is associated with reading fluency and brain activity during reading.…”

“…This grapheme-phoneme bind created during cross modalities network coactivation, has been described as a key step for developing fluent reading (Chyl et al, 2018 ; He et al, 2021 ) by enhancing the specialized visual areas related to print when presented with the corresponding letter-speech sound. This process typically occurs in the early learning stages of reading (Ehri, 2005 ; Fraga-González et al, 2021 ). As an example of this effect in EEG studies, it has been shown that ERP amplitudes (for the mismatch responses MMN and LDN, for example) were enhanced when speech sounds were presented to typical readers with letters—an effect that was absent in dyslexic readers (Froyen et al, 2009 )—suggesting that in atypical reading development, this letter-speech bind is absent or very weak.…”

Data_Sheet_1.docx

“…However, the nature of the link between the two modalities remains unclear (Gibson et al, 2006;Wright and Conlon, 2009;Blau et al, 2010;Georgiou et al, 2012;Ye et al, 2017;Rüsseler et al, 2018;Stein, 2018). Several studies have investigated this relationship using simultaneous auditory and visual stimuli in dyslexic vs. typical readers using behavioral and brain measures (Aravena et al, 2018;Karipidis et al, 2018;Fraga-González et al, 2021). In the present study, we investigated the extent to which speech processing at the brain level is associated with reading fluency and brain activity during reading.…”

“…This grapheme-phoneme bind created during cross modalities network coactivation, has been described as a key step for developing fluent reading (Chyl et al, 2018;He et al, 2021) by enhancing the specialized visual areas related to print when presented with the corresponding letter-speech sound. This process typically occurs in the early learning stages of reading (Ehri, 2005;Fraga-González et al, 2021). As an example of this effect in EEG studies, it has been shown that ERP amplitudes (for the mismatch responses MMN and LDN, for example) were enhanced when speech sounds were presented to typical readers with letters-an effect that was absent in dyslexic readers (Froyen et al, 2009)-suggesting that in atypical reading development, this letter-speech bind is absent or very weak.…”