Based on previous research, the Nc was analyzed in the 300–700 msec time meantime window in a fronto-central region of interest. Based on visual inspection, a later time window showing a PSW from 700

to 1200 msec was analyzed using the same region of interest. Data were analyzed with repeated measures analysis of variances (ANOVAs) on the mean amplitude values with the within-subject factors Condition (standard, location change, object change, switch) and Electrode (Fz, FC1, FCz, FC2, Cz). Greenhousse-Geisser correction for nonsphericity (Greenhouse and Geisser 1959) was applied whenever appropriate. Corrected P values are reported along with original degrees of freedom. Results Figure ​Figure2A2A shows Inhibitors,research,lifescience,medical the waveforms at the five fronto-central electrodes included in the analyses and Figure ​Figure2B2B shows the topographical distribution of ERP effects across the scalp. A fronto-central negativity (Nc component) was elicited in all conditions

between 300 and 700 msec, which was larger in the Inhibitors,research,lifescience,medical standard condition than in the other conditions. The waveforms in the oddball conditions included ~12 trials, and the waveforms in the standard condition contained 110 trials. The reason for including all trials in the standard condition was to establish a solid baseline with maximized signal-to-noise ratio to compare the oddballs to. To show that the size of the Nc component was not affected by the difference in number of trials included in Inhibitors,research,lifescience,medical the averages, Inhibitors,research,lifescience,medical Figure S3 shows the standard including all trials as compared to the standard including ~12 trials, an amount equal to what was used the oddball conditions. An ANOVA in the 300–700 msec time window with the factors Condition and Electrode confirmed the

finding of the Nc effect. The results showed a main effect of Condition (F (3,48) = 4.41, P = 0.008), an effect of Electrode (F (4,64) = 6.95, P < 0.001), and no interactions (F (12,192) = 1.05, P = 0.390). Location change, object change, and switch all elicited a smaller negativity than the standard, resulting in a positive effect relative to the standard in this time window (Fig. ​(Fig.2B).2B). A priori contrasts Inhibitors,research,lifescience,medical revealed that this effect was significant in all conditions: location change versus standard (F (1,16) = 9.77, P = 0.007), object change versus standard (F (1,16) = 12.76, P = 0.003), and switch versus standard (F (1,16) = 17.75, P = 0.001). In the 700–1200 Cilengitide msec time window, a PSW was elicited in the object change condition and location change condition, while the switch condition did not deviate from the standard in this latency window. The ANOVA revealed no significant effects of Condition and Electrode, and no interaction (all F < 1.44, n.s.). However, a priori contrasts showed that the object change and location change differed significantly from the standard (F (1,16) = 4.92, P = 0.041, F (1,16) = 4.55, P = 0.049 respectively), whereas the switch did not (F (1,16) <1, n.s.). Figure 2 Event-related potential (ERP) data.