97, Q-tip, M = 52.52, selleck F1,17 = 4.39, P = 0.052; nonpainful stimuli: needle, M = 19.41, Q-tip, M = 20.05, F1,17 = 1.27, P = 0.276). To further investigate whether the effects on pain ratings were influenced by habituation to electrical stimuli,

ratings were subjected to three-way anovas comprising the factors electrical stimulation, visual stimulation and time (first and last 50% of trials). This analysis did not reveal significant effects in relation to the factor time, suggesting that habituation effects did not substantially contribute to the present findings. PDR traces for needle and Q-tip clips (pooled across nonpainful and painful trials) are depicted in Fig. 1C. The dilation started at about 0.4 s after clip onset. PDR traces to needle and Q-tip clips already differed before electrical stimulus onset. A running t-test between both PDR traces revealed significant differences between the clips starting from about check details −0.3 s before electrical stimulus onset until

the end of the trial. For the correlation analysis, we selected the time interval based on our previous study (Höfle et al., 2012) from −0.2 s before to 0.6 s after electrical stimulus onset. Data points were averaged within the interval to obtain a single value for further analyses. The correlation analysis conducted on the average effect (needle minus Q-tip) across participants revealed a significant positive relationship between PDR and perceived unpleasantness (r17 = 0.48, P = 0.046). This finding directly replicated the results of our previous study (Höfle et al., 2012), where a positive correlation of r24 = 0.49 was found for this analysis. A cluster-based analysis on mean ERP values computed over all electrodes and a time

interval from −1 to 0 s revealed significant differences between viewing needle pricks and Q-tip touches from about −0.4 to −0.1 s (illustrated by means of a running t-test in Fig. 2A) and at right-central electrodes, i.e. contralateral to the forthcoming electrical stimulation (Fig. 2B). The mean ERP traces for these electrodes showed a slow negative potential cAMP within the time interval of interest, which was more pronounced when viewing needle clips compared with Q-tip touches (Fig. 2C). In the following, we will refer to this slow negative potential as stimulus-preceding negativity (SPN; e.g. Brunia & van Boxtel, 2001). Mean ERP amplitudes (−0.4 to −0.1 s) at right-central electrodes were selected for the further correlation analyses. Time–frequency representations (5–30 Hz) of total oscillatory responses at right-central electrodes showed an initial increase in the alpha band peaking at about 0.1–0.2 s after clip onset (Figs 3A and 4). The alpha power increase was maximal at occipital sites (Fig. 3B, first row). Following the increase, a reduction of ABA was found, which was strongest at right-central electrodes (Fig. 3B, last row).