Mental effort affects vigilance enduringly: after-effects in EEG and behavior.

Vigilance is assumed to decline with sustained task performance. The EEG-effects during performance on mental tasks, however, cannot be ascribed indisputably to vigilance decline per se. During task performance itself, effects of information processing and vigilance decline may be confounded. In this study, effects of sustained mental effort were studied in the absence of specific information processing, after sustained information processing had taken place, namely after an effortful 70-min intelligence test. Vigilance was determined by means of EEG-measures in a rest condition. Furthermore, behavioral performance was assessed on two different tasks, the traditional Clock test and the SART. After mental effort, theta power in the EEG and errors on the SART were increased. Beta2 power, however, also appeared enhanced. We conclude that sustained mental effort produces an enduring decrease in vigilance, but that some active processing is enhanced at the same time. A second study replicated the EEG-results after mental effort. Copyright 2004 Elsevier B.V.