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

•Variability of connectivity reflects the ADHD status better than connectivity itself.•Enhanced variability of nonlinear EEG connectivity characterizes ADHD at rest.•Changes between states only occur in variability of theta band connectivity for ADHD.

ObjectiveTo assess ADHD from global measures of EEG functional connectivity and their temporal variability in different resting states.MethodsEEGs 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.ResultsThe 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).ConclusionsThe 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.SignificanceThe underlying neural dysfunctions producing the ADHD seem better reflected by the CV measurements.