The visual analogue scale, which was superimposed over the finger of the hand on the screen, ranged between 0 and 100 on the vertical intensity axis (0, no sensation; 40, beginning of pain experience, marked by a horizontal line; 100, most intense pain) and 0 and 100 on the horizontal unpleasantness axis (0, not unpleasant at all; 100, extremely unpleasant). The visual analogue scale remained on the screen for 2 s. As the rating procedure was trained beforehand, this time interval was sufficient to respond adequately. Prior to the experimental session, the experimenter instructed participants to rate the perceived intensity and unpleasantness of electrical
stimuli, but not how intense or unpleasant the Selleck Venetoclax visual stimulation appeared. Each experimental session consisted of 15 blocks comprising 48 trials each; 50% of all needle, Q-tip or hand-alone trials were associated with painful stimulation (i.e. eight out of 16 trials per clip and block). Prior to each block, the eye-tracking system was calibrated and, after the experimental session, participants rated the degree of embodiment of the hand seen on the screen. Ku-0059436 To measure the degree of experienced embodiment of the hand viewed on the screen, a questionnaire
was used that addressed factors predictive for the proprioceptive delusion observed in classic studies on the rubber hand illusion (adapted from Longo et al., 2008). The questionnaire comprised
10 items including questions on ownership (e.g. ‘It seemed like I was looking directly at my own hand, rather than at a videotaped hand’), location (e.g. ‘It seemed like my hand was in the Etofibrate same location as the hand in the clip’), and agency (e.g. ‘It seemed like I was in control of the hand on the screen’). All questions were rated on a six-point Likert scale (1, ‘strongly disagree’; 6, ‘strongly agree’). The original questionnaire (Longo et al., 2008) was translated into German and the wording was slightly modified as a videotaped hand instead of a rubber hand was used in the present study (i.e. the term ‘rubber hand’ was replaced by ‘hand in the clip’). High-density EEG recordings were acquired using a passive electrode system (EASYCAP) with 126 scalp electrodes and two electro-oculogram electrodes below the eyes. The data were recorded with a passband of 0.016–250 Hz and digitised with a sampling rate of 1000 Hz using a BrainAmp amplifier system (Brain Products). EEG data were online recorded against a nose tip reference and offline rereferenced to common average. The data were analysed using Matlab (MathWorks), EEGLAB (http://www.sccn.ucsd.edu/eeglab; Delorme & Makeig, 2004) and FieldTrip (http://www.ru.nl/fcdonders/fieldtrip; Oostenveld et al., 2011). For the offline analysis, data were bandpass filtered between 0.3 and 125 Hz and downsampled to 500 Hz. A narrow band notch filter (49.8–50.