SINGLE TRIAL VARIABILITY WITHIN THE P300 (250-500 MS) PROCESSING WINDOW IN ADOLESCENTS WITH ATTENTION-DEFICIT HYPERACTIVITY DISORDER

The traditional averaging process used to derive event related potenti al components (ERPs) is a soundly based method of determining the unde rlying ERP. Averaging, however, ignores the variability due to the sin gle-trial ERPs that constitute the traditional average ERP. This varia bility may reflect complementary functional information to the average measure. Our group applied a simple procedure, the response variance curve (RVC), which measures single-trial ERP variability relative to t heir average. In this study, the average ERP and RVC measures (generat ed from the same single-trial task-relevant target ERPs) were assessed in an auditory oddball paradigm, in 17 unmedicated male adolescents w ith attention deficit hyperactivity disorder (ADHD) and in 17 age- and sex-matched normal controls. P300 amplitude, latency and point of max imum variability of the RVC were measured within the P300 processing w indow (250-500 ms post-stimulus). There were no significant difference s in P300 amplitude or latency between the groups. Unmedicated ADHD pa tients, however, showed significantly increased single-trial variabili ty within the P300 window compared with controls. This variability was significantly reduced with stimulant medication. (C) 1997 Elsevier Sc ience Ireland Ltd.