TOPOGRAPHIC MAPPING OF CORTICAL POTENTIALS-EVOKED BY DISTENSION OF THE HUMAN PROXIMAL AND DISTAL ESOPHAGUS

We describe cortical potentials evoked by balloon distension of the pr oximal and distal oesophagus in 8 healthy right handed volunteers. Oes ophageal stimulation was performed using a pump which rapidly inflated a 2 cm silicone balloon positioned either 3 cm distal to the upper oe sophageal sphincter or 5 cm proximal to the lower oesophageal sphincte r, at a frequency of 0.2 Hz, using inflation volumes which produced a definite but not painful sensation. Oesophageal evoked cortical potent ials were recorded in all subjects with an initial negative and positi ve component (N1 and P1), followed by a second negative and positive c omponent (N2 and P2) in 6 subjects. The morphology and the scalp topog raphy of the N1 component elicited by proximal and distal oesophageal stimulation suggests activation of the primary somatosensory cortex an d/or the insular. There was also evidence for hemispheric dominance fo r the N1 potential which was independent of handedness. The frontal em phasis of the proximal oesophageal N1 component, in contrast to the ce ntral emphasis of the distal oesophageal N1 component, suggests that d ifferent neuronal populations were activated by stimulation of the two sites. The frontal emphasis of the ensuing P1 component from both oes ophageal sites suggests that it originates in a separate precentral so urce. The topography of the N2 components obtained by stimulation of e ither oesophageal site was similar to that of the N1 component, sugges ting that they originate in similar areas of the cortex. The P2 compon ent evoked by stimulation of both oesophageal sites was localised at t he vertex. The inter- and intra-subject variation in the morphology of the N2 and P2 components suggests that secondary cortical processes r elated to cognition may be involved in their generation.