The variability of EEG functional connectivity of young ADHD subjects in different resting states

Abstract

Objective: To assess ADHD from global measures of EEG functional connectivity and their temporal variability in different resting states.

Methods: EEGs from sixteen cortical regions were recorded at rest during eyes-closed (EC) and eyes-open (EO) in 10 male combined-type ADHD subjects and 12 healthy male controls. The mean global connectivity (CM) of each region and its temporal variability (CV) were estimated from a number of EEG segments recorded in both states. Connectivity indices between regions were calculated using the magnitude squared coherence (Coh) in the delta(δ)/theta(θ)/alpha(α)/beta(β) frequency bands and the nonlinear index (L) of generalized synchronization.

Results: The CM did not present between-group differences in any region or state. However, the CV exhibited state-independent differences between both groups (ADHD>controls) mainly in frontal and parieto-occipital regions for all indices except Coh(α). Within group, only the CV-Coh(θ) of the centro-temporal region increased significantly for the ADHD subjects from EC to EO (p<0.001) and was greater than controls in EO (p<0.001).

Conclusions: The CV of index-L and of Coh(θ) seem to be the best state-independent and -dependent measurements, respectively, to discriminate ADHDs from control subjects using resting state EEG data.

Significance: The underlying neural dysfunctions producing the ADHD seem better reflected by the CV measurements.

Keywords: ADHD; Coherence; EEG; Functional connectivity; Generalized synchronization; Resting state.