Validation of reaction time in continuous performance tasks as an index ofattention by electrophysiological measures

The relationship between behavioral reaction time (RT) and event related po tential (ERP) variables (N2, P3 measuring perceptual and attentional proces sing was studied in continuous performance tasks (CPT). ERPs provide on-lin e measures of cerebral processing and the purpose of the study was to provi de normative data and to use ERP-derived information to facilitate interpre tation of reaction time data. In Study 1 a normal group (N = 51) performed CPTs of varying complexity, and the results indicated that in simple tasks a fast process reflecting perceptual classification and orientation of atte ntion (N2) is involved, whereas a physiological marker of a controlled atte ntion process reflected in P3 latency is related to RT in more complex task s. In Study 2 normal subjects (N = 12) performed CPTs with instruction to d eliberately vary RTs. Despite wide variation in behavioral RTs, ERP measure s reflecting attention (N2,P3) show little influence of instruction, while late occuring components (SW) measured at fronto-central electrodes are aff ected. In neuropsychological assessment efforts have been made to develop s ymptom validity indicators, and the results show that ERPs are important me asures for interpreting cerebral and motivational mechanisms underlying beh avioral RTs.