, 2000 and Vogt et al., 1998) whereas during actual task performance, small power (large event related desynchronization or ERD) is related to good performance (e.g., Doppelmayr et al., 2005 and Klimesch et al., 1997). Most interestingly for perceptual performance (in tasks target detection under threshold or near threshold conditions), small prestimulus alpha power (Ergenoglu et al., 2004) and a small ERD or even event related synchronization (ERS) during actual task performance (Hanslmayr et al., 2005) is predictive for good performance. A variety of studies have meanwhile documented

that a state CAL-101 in vitro of low prestimulus alpha power is associated with improved detection and discriminability of threshold-level stimuli (Hanslmayr et al., 2007a, Mathewson et al., 2009, Romei et al., 2007, Romei et al., 2008 and Van Dijk et al., 2008). There is, thus, good evidence for a double dissociation between pre- and poststimulus alpha power and the type of cognitive

PLX4032 in vitro performance. Good memory performance is associated with large prestimulus but small poststimulus alpha power, whereas good perception performance is related to small prestimulus power with little or no ERD during perception performance. We have interpreted these findings in terms of cortical inhibition and excitation preceding task performance. Perception performance appears to be enhanced if the cortex already is activated (as indicated by small prestimulus power), whereas memory performance is enhanced if the cortex is

not activated (as indicated by large prestimulus power) before a task is performed. This interpretation is quite plausible if we assume Wilson disease protein that for visual target detection a high level of cortical excitation will be helpful to analyze a visual input. When a specified and well known target must be detected, memory traces are probably ‘preactivated’ and as a consequence inhibition must be reduced. For memory performance, on the other hand, an initial (prestimulus) activation of the cortex may be detrimental because it may interfere with (or even suppress) the high selectivity that is required for accessing a memory trace during actual task performance. In considering these findings and their interpretation, let us now make predictions for a traditional spatial cuing task in which a target must be detected in the right or left visual field. The prediction for prestimulus alpha power at the contralateral side is a decrease in power, whereas for the ipsilateral side, we expect an increase in power. Because the functional meaning of the P1 amplitude is similar to that of ongoing alpha, we also expect a larger ipsilateral P1. We have tested this prediction in Experiment 1 of the study by Freunberger et al. (2008a). As observed in other studies (e.g., Busch et al. 2004), we also found that the P1 is larger over ipsi- as compared to contralateral recording sites. In our study (using a type 2 paradigm with a jittered ISI between cue and target; cf. Freunberger et al.