The study includes Graph Theoretic advanced EEG analysis in order to investigate the impact of pharmacological treatment with osmotic release oral system-methylphenidate for a month in 18 boys (aged between 7-12 years) with Attention-Deficit-Hyperactivity Disorder, combined type. In analysis, neurofunctional dependency levels across the cortex are estimated by using six different connectivity estimation approaches based on three separate domains such as time (Pearson Correlation, Spearman Correlation), frequency (Directed Transfer Function, Partial Directed Coherence) and phase (Phase Locking Value, Phase Lag Index). All methods are examined for eyes-opened resting-state EEG segments of 2 sec over a single trial of 1 min in both pre- and post-treatment recordings. Then, five quantitative brain network indices of transitivity, clustering coefficients, assortativity, global efficiency and modularity are computed from connectivity estimations.
Performance of connectivity estimators are compared to each other with respect to two-class classifications (pre-treatment features vs post-treatment features) by using Support Vector Machines driven by brain network indices. The highest classification accuracy of 80.74% is obtained with Pearson Correlation. Statistical one-way Anova test, pair-wise multiple comparison test and step-wise logistic regression modelling are all used to observe the most sensitive network index estimated from Pearson Correlations. In addition to quantitative results, statistical box-plots of the estimated network indices are shown graphically. When modularity index is excluded from the features, classification accuracy is increased to 83.79%. Overall results reveal that brain segregation and resilience are increased by the treatment. In particular, the most meaningful brain network measures can be estimated from time domain statistical correlations between resting-state eyes open EEG segments in order to understand the alterations in neuronal transmission mechanism across the cortex in response to a specific treatment in pediatric psychiatry.