Investigating brain electrical activity and functional connectivity in adolescents with clinically elevated levels of ADHD symptoms in alpha frequency band.

EEG measures such as power and connectivity have been widely used to investigate the neuronal underpinnings of ADHD. Traditionally, the fixed band analysis, in which a single frequency band is applied to all the subjects, has been used to estimate these EEG measures. However, there are important interindividual differences in the predominant frequency of alpha-band oscillations. In this study, we present an individualized estimate of EEG in the alpha band and compared the results with traditional fixed band analysis. We also examined the EEG profile separately in lower and upper alpha bands. We further examined the association between EEG measures and ADHD symptoms. Eyes closed resting EEG was collected from 21 adolescents with clinically elevated levels of ADHD and 21 age and gender matched control subjects. Spectral power and connectivity were computed in lower and upper alpha bands. Results revealed a dissociation between upper and lower alpha band power and connectivity in ADHD. The ADHD group showed reduced power and connectivity in the lower alpha band and an elevation of upper alpha power compared to the Control group. EEG power in the lower alpha band was negatively associated with ADHD severity. Our results, however, did not provide conclusive evidence for IAF as an overall greater measure of EEG compared to the traditional fixed band method.