Human electroencephalography (EEG) noninvasively measures ongoing resting-state brain electrical activity. These oscillations are divided into frequency bands (delta (1–3 Hz), theta (4–7 Hz), alpha (8–12 Hz), beta (13–28 Hz) and gamma (>29 Hz)), with each band reflecting a different global brain state (for example, alpha activity reflects a relaxed state while beta EEG reflects an alert awake state1–3). Although local excitatory–inhibitory interactions underlying sensory and motor functions involve gamma-band oscillations, cognitive functions mediated by long-range cortical interactions often involve EEG activity in the beta range.3 Beta EEG is also associated with several externalizing disorders,4–10 including alcohol and other substance use disorders (SUDs) and attention deficit hyperactivity disorder (ADHD). Given these associations, and the high degree of genetic influence observed in twin studies (49–85%11,12), beta EEG has been proposed as a useful endophenotype13 for identifying genetic factors underlying disorders characterized by disinhibitory traits.14
