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5 s from target onset. This is the procedure employed in most other dual task AUY-922 supplier studies with ERPs (e.g., Hohlfeld et al., 2004; Lien et al., 2008), to which the present data were to be compared. The dual task paradigm provides a particular challenge to ERP methodology, because each stimulus and response is related to a complex set of brain waves that overlap in different ways depending on the SOA. This makes it difficult to disentangle effects in the composite waveforms. However, it is possible to isolate ERP components that relate to only one experimental factor by eliminating invariant overlapping activity with a subtraction procedure. This is in accordance with the assumption of Nunez (1981) that electric fields of several sources combine linearly without interacting. The logic of subtraction works if the overlapping activity is the same in the two subtracted conditions. Examples for this approach to dual task designs are studies by Luck (1998), Osman and Moore (1993), Sommer, Leuthold, and Schubert (2001), and Hohlfeld et al. (2004). This logic was also applied in the present study in order to isolate the N400 as well as the P600 B3GAT3 component. Both components were obtained by subtracting ERPs to acceptable targets from those to unacceptable targets within each SOA. In this way we were able to isolate the electrophysiological response to word incongruity for conditions of different temporal overlap. Mean amplitude measures were calculated in two 200-ms time windows between 100 to 300 and 400 to 600 ms relative to the onsets of the critical words. The second window was chosen around the peak of the N400 component; the first window served to test a conspicuous effect seen in the wave shapes (cf. Fig. 2B). In addition, six consecutive 100-ms time windows between 650 and 1150 ms covered the typical time range of the P600 effects. ERP amplitude measures were submitted to ANOVAs, with repeated measures on factors SOA (3 levels), acceptability (2 levels), and electrode site (27 levels) as SCH 900776 manufacturer independent variables. Error rates were subjected to ANOVAs, with repeated measurements on SOA and acceptability. If appropriate, degrees of freedom were corrected according to Huynh and Feldt (1976). Due to the fact that responses were only given after the sentence, reaction times for the sentences cannot be considered to represent processing times for the critical words and were therefore disregarded. Results Performance Error rates were higher for acceptable than unacceptable sentences (M = 20.4 vs. 15.0 %, SE = 1.89 vs. 2.39), F(1, 16) = 5.65, p