Chapter 6 – EEG imaging 195 II; Medoc Advanced Medical Systems, Ramat Yishai, Israel). During the calibrations and baseline phases, both arms were used for pain stimulations. During the nocebo phase, only the right arm was used (Fig. 1b). Throughout the experiment, pain intensities were rated on a numeric rating scale (NRS) ranging from 0 (no pain) to 10 (worst pain imaginable in this context). Sensory and pain thresholds Before the start of the experimental phases, warmth and pain threshold levels were tested for each participant, heat stimuli were applied and participants were asked to indicate the first moment at which they perceived warmth and pain. After a practice trial for each, the average of 3 warmth detection values and 3 heat pain detection values determined the thresholds for warmth and pain, respectively. This method follows published standardized procedures 27. Pain calibration protocol Pain calibrations were conducted in order to determine the temperatures that would induce moderate and high pain during baseline and nocebo phases. The calibrations were individually tailored, based on the NRS ratings of 16 heat stimuli of varying intensities. Throughout the experiment, each pain stimulus was initiated from a 32°C baseline, increased to a target temperature, and presented for 10 seconds at plateau. The ramp up and return rates were 8°C per second. During calibrations the inter-stimulus interval (ISI) was 5 seconds, during which NRS pain ratings were given. Median temperatures rated as NRS 3 to 5
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