Figure 1.

Schematic representation of the study design. The effects of deactivating cTBS transcranial stimulation on the pain-intensity ratings of intranasal nociceptive stimuli (500-ms pulses) of gaseous carbon dioxide (CO₂) at 4 different concentrations (35, 50, 65, or 80% vol/vol) were assessed using 3 main experimental conditions comprising either (1) cTBS of the primary motor cortex (M1) hand representation (“M1 verum”), or (2) cTBS of the secondary somatosensory cortex S2 (“S2 verum”), or (3) sham stimulation. The experimental conditions were assessed at random order at separate days scheduled at an interval of at least 1 week. During each study day, 2 experimental sessions with nociceptive stimulation, pain-intensity ratings, and fMRI imaging were performed. After the baseline session, cTBS (or sham) was applied according to the respective study condition. During each session, subjects received 80 CO₂ stimuli (20 stimuli for each of 4 different and randomly distributed strengths) at long randomly spaced intervals of 13.5 to 28.2 seconds. After a randomized interval of 3.4 to 6.6 seconds, the stimulus intensity is estimated on a visual analogue scale (enlarged section top left). cTBS, continuous theta-burst stimulation; fMRI, functional magnetic resonance imaging.