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

The relationship between behavioral reaction time (RT) and event related potential (ERP) variables (N2, P3) measuring perceptual and attentional processing was studied in continuous performance tasks (CPT). ERPs provide on-line measures of cerebral processing and the purpose of the study was to provide normative data and to use ERP-derived information to facilitate interpretation 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 attention (N2) is involved, whereas a physiological marker of a controlled attention process reflected in P3 latency is related to RT in more complex tasks. In Study 2 normal subjects (N = 12) performed CPTs with instruction to deliberately vary RTs. Despite wide variation in behavioral RTs, ERP measures reflecting attention (N2,P3) show little influence of instruction, while late occuring components (SW) measured at fronto-central electrodes are affected. In neuropsychological assessment efforts have been made to develop symptom validity indicators, and the results show that ERPs are important measures for interpreting cerebral and motivational mechanisms underlying behavioral RTs.