Fig. 2

Modulation of somatosensory evoked brain potentials by selective attention and heterotopic noxious counter-stimulation (HNCS). Grand average somatosensory evoked potentials (SEP) recorded at Cz and scalp topography of components showing significant modulation by selective attention and HNCS (N100 and P260) are presented for each block, session, and group (patients with IBS, left column; control group, right column). The three components that were analyzed (P45, N100, and P260) are indicated on the bottom left panel. For mean amplitudes of the components and statistical results, see Table 2, Fig. 3, and the results section. X-axis, time in ms; Y-axis, amplitude in μV. IBS: irritable bowel syndrome; HICS: heterotopic innocuous counter-stimulation; HNCS: heterotopic noxious counter-stimulation