First-stage theta power with psychiatric symptoms and dimensions (anxious-depression (AD), compulsive behavior and intrusive thought (CIT) and social withdrawal (SW)). Theta power was measured at mid-frontal electrode sites (Fig. 8B). A, Grand average waveforms of first-stage theta power comparing the top/bottom 50th percentile (N = 96/group) individuals based on their compulsivity (CIT) estimates. Single-trial analyses (with all participants) indicate that highly compulsive individuals exhibit a decrease in theta power (β = –0.03, SE = 0.01, p = 0.03). In contrast, first-stage alpha power was not associated with compulsivity (Fig. 8A). B, Reduced theta power at first stage was linked to several questionnaire scores, but the effect was ultimately specific to compulsivity. The y-axis shows the change in theta power (in square microvolts) as a function of a 1 SD increase of psychiatric questionnaire/dimension scores. Error bars denote SEs. *p < 0.05.