Gregory L Hanna, Yanni Liu, Barbara S Hanna, Paul D Arnold, William J Gehring
Attention-deficit/hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) are common psychiatric disorders that may be differentiated by neurocognitive measures and electrocortical indices of performance monitoring. Increased reaction time variability (RTV) is a consistent finding in studies of ADHD. The error-related negativity (ERN) and error positivity (Pe) are components of the event-related potential (ERP) following an error that are potential mechanistic biomarkers for both disorders. The correct response negativity (CRN) and correct positivity (Pc) are components of the ERP following a correct response that are less well understood. The study examined RTV, accuracy, and neural indices of error monitoring using an Eriksen flanker task in 84 ADHD cases, 90 OCD cases, and 136 matched healthy controls (HC) ages 8 to 18 years. Both correct and error trial RTV were significantly increased in ADHD cases compared to HC, whereas flanker task accuracy was significantly decreased in OCD cases relative to HC. Compared to HC, CRN amplitude was significantly increased, and Pe amplitude was significantly decreased in ADHD cases. ERN amplitude was significantly increased in OCD cases compared to HC. Compared to HC, the difference between Pe and Pc amplitudes was significantly decreased in both ADHD and OCD cases, which may reflect defects in the post-decisional evidence accumulation process that impair decision accuracy or subsequent behavioral adjustments in those disorders. In two multiple linear regression analyses, correct trial CVRT had significant associations with age, ADHD behaviors, and CRN, Pe, and Pc amplitudes. The study provides new evidence of increased RTV in ADHD, differential alterations in error-related and correct-related brain activity in ADHD and OCD, and a robust association between RTV and the error monitoring neural system.