EEG based functional brain networks analysis in dyslexic children during arithmetic task

Abstract

Developmental Dyslexia is a neuro-developmental disorder that often refers to a phonological processing deficit regardless of average IQ. The present study investigated the distinct functional changes in brain networks of dyslexic children during arithmetic task performance using an electroencephalogram. Fifteen dyslexic children and fifteen normally developing children (NDC) were recruited and performed an arithmetic task. Brain functional network measures such as node strength, clustering coefficient, characteristic pathlength and small-world were calculated using graph theory methods for both groups. Task performance showed significantly less performance accuracy in dyslexics against NDC. The neural findings showed increased connectivity in the delta band and reduced connectivity in theta, alpha, and beta band at temporoparietal, and prefrontal regions in dyslexic group while performing the task. The node strengths were found to be significantly high in delta band (T3, O1, F8 regions) and low in theta (T5, P3, Pz regions), beta (Pz) and gamma band (T4 and prefrontal regions) during the task in dyslexics compared to the NDC. The clustering coefficient was found to be significantly low in the dyslexic group (theta and alpha band) and characteristic pathlength was found to be significantly high in the dyslexic group (theta and alpha band) compared to the NDC group while performing task. In conclusion, the present study shows evidence for poor fact-retrieval mechanism and altered network topology in dyslexic brain networks during arithmetic task performance.

Keywords: Arithmetic task; Developmental dyslexia; EEG; Functional connectivity; Graph theory; Network analysis.

Fig. 1

Arithmetic task details used in this study

Fig. 2

EEG recording procedure

Fig. 3

Wavelet decomposition tree

Fig. 4

Block diagram of an overall methodology

Fig. 5

Functional connectivity maps for the dyslexic group during task and baseline conditions (Graphs are thresholded only to show highly significant connections and red-circled nodes had high significant difference and high node strength (p < 0.0005) between condition)

Fig. 6

Functional connectivity maps for NDC group during task and baseline conditions (Graphs are thresholded only to show highly significant connections and red-circled nodes had high significant difference and high node strength (p < 0.0003) between condition)

Fig. 7

Event related changes in node strength between dyslexic and NDC group a Delta band, b Theta band, c Alpha band, d Beta band, e Gamma band

Fig. 8

Comparison of event-related changes in the CC, CPL and SW between groups