This hypothesis was actually tested with an fMRI study evaluating the overlap between sustained and transient activation patterns across long-term memory (LTM), attentional, and WM tasks. The results confirmed the shared PFC recruitments in WM and LTM tasks only for transient item-related responses (Marklund et al. 2007). Therefore, there is substantial evidence that the SME is related to

transient attentional processes. Furthermore, there is also some empirical proof for an involvement of prefrontal activation and frontal negativity in sustained attention, even in task switching paradigms, where it is important to maintain internal representations of multiple task sets over a prolonged time (Braver Inhibitors,research,lifescience,medical et al. 2003; Barcelo et al. 2006; Gladwin et al. 2006). The few studies, however, that directly compared the ERPs of task switching with task repetition provided mixed results (Wylie et al. 2003; Gladwin et al. 2006). It is therefore still unclear, as to what extent Inhibitors,research,lifescience,medical sustained attention contributes to the SME. Another study on encoding-related activity using a task switch paradigm showed the contribution of both sustained and transient attentional processes in the determination of the SME (Otten et al. 2010). However, the findings did not Inhibitors,research,lifescience,medical reveal any difference between the effects of stay and switch trials, associated, respectively, with

sustained and transient processes. Based on this evidence, we Inhibitors,research,lifescience,medical expected to find the frontal negative ERP activity associated with the prestimulus SME in both stay and switch conditions. Moreover, we expected to observe a different timing of

the occurrence of the SME in the two conditions related to the nature of the underlying attentional mechanisms. In fact, according to the dual network model of attentional control (Dosenbach et al. 2008) sustained and transient attentional processes act in parallel but relatively independent in time. Transient processes are primarily involved in task switching ensuring goal-directed adjustments to the task requirements and sustained processes provide a stable background over the Inhibitors,research,lifescience,medical whole epoch. Hence, in stay learn more trials sustained processes reflecting set maintenance would prevail at the beginning of the trial, extending their influence across the entire epoch. In switch trials transient processes would prevail before stimulus onset reflecting an efficient adjustment to the task demands. Methods Participants Twenty-one right-handed healthy students (mean age 22.3; four men) participated for course credits. All participants were native Adenylyl cyclase German speakers. All had normal or corrected-to-normal vision. The experimental data were collected after obtaining informed written consent from each subject. The study was approved by the local ethics committee. All data were recorded at the Institute of Psychology of the University of Bern. Stimulus and materials Four hundred and thirty-two concrete nouns were selected from a database of written German words (Baayen et al. 1995).