Fig. 3

Modulation of somatosensory evoked brain activity by selective attention and heterotopic noxious counter-stimulation (HNCS). Amplitude (mean ± SEM) of the N100 and P260 components (a, b, respectively) for each block, session, and group (patients with IBS, left column; control group, right column). For mean amplitudes of the components and statistical results, see Table 2 and “Results” section. The inhibitory effect of HICS and HNCS compared with baseline within each session is represented by the *, ^†, and ^‡ symbols. *p < 0.05, ^†p < 0.01, ^‡p < 0.001. The inhibitory effect of HNCS compared with HICS vs. the corresponding changes in the control session is represented by the # symbol. The inhibitory effect of HICS compared with baseline and HNCS compared with HICS vs. the corresponding changes in the attention to shock pain session are represented by the & symbol. ^#p < 0.001; ^&p < 0.05. X-axis, conditions and sessions; Y-axis, amplitude in μV. NRS: numerical rating scale; SEM: standard error of the mean; IBS: irritable bowel syndrome; HICS: heterotopic innocuous counter-stimulation; HNCS: heterotopic noxious counter-stimulation