ELSEVIER Electroencephalographyand clinical Neurophysiology 96 (1995) 219-228 o Topographic mapping of cortical potentials evoked by distension of the human proximal and distal oesophagus Q. Aziz a, P.L. Furlong d, *, j. Barlow a, A. Hobson a, S. Alani u, j. Bancewicz a, M. Ribbands c, G.F.A. Harding d, D.G. Thompson a a Department of Gastroenterology, Hope Hospital, Unicersily of Manchester, Manchester, UK b Department of Neurophysiology, Hope Hospital, UniL'ersity of Manchester, Manchester, UK Department of Medical Physics, ttope Hospital, Unit ersity of Manchester, Manchester, UK d Department of Vision Sciences, Aston UniL,ersity, Aston Triangle, Birmingham B4 7ET, UK Accepted for publication: 4 November 1994 Abstract We describe cortical potentials evoked by balloon distension of the proximal and distal oesophagus in 8 healthy right handed volunteers. Oesophageal stimulation was performed using a pump which rapidly inflated a 2 cm silicone balloon positioned either 3 cm distal to the upper oesophageal sphincter or 5 cm proximal to the lower oesophageal sphincter, at a frequency of 0.2 Hz, using inflation volumes which produced a definite but not painful sensation. Oesophageal evoked cortical potentials were recorded in all subjects with an initial negative and positive component (N1 and P1), followed by a second negative and positive component (N2 and P2) in 6 subjects. The morphology and the scalp topography of the N1 component elicited by proximal and distal oesophageal stimulation suggests activation of the primary somatosensory cortex and/or the insular. There was also evidence for hemispheric dominance for the N1 potential which was independent of handedness. The frontal emphasis of the proximal oesophageal N1 component, in contrast to the central emphasis of the distal oesophageal N1 component, suggests that different neuronal populations were activated by stimulation of the two sites. The frontal emphasis of the ensuing P1 component from both oesophageal sites suggests that it originates in a separate precentral source. The topography of the N2 components obtained by stimulation of either oesophageal site was similar to that of the N1 component, suggesting that they originate in similar areas of the cortex. The P2 component evoked by stimulation of both oesophageal sites was localised at the vertex. The inter- and intra-subject variation in the morphology of the N2 and P2 components suggests that secondary cortical processes related to cognition may be involved in their generation. Keywords: Oesophagus; Striated muscle; Smooth muscle; Topography; Cerebral cortex 1. Introduction Cortical evoked potentials were first recorded by Daw- son in 1947, since when the technique has been used widely to assess the integrity of visual (Halliday, 1993), auditory (Starr and Hamilton, 1976; Chiappa et al., 1979) and somatic (Nofil and Desmedt, 1980) afferent pathways. By studying the spatio-temporal distribution of these po- tentials, information about their cortical sources has also been obtained (Duffy, 1986). * Corresponding author. Tel.: +44 21 3593611; Fax: +44 21 3334220. Cortical potentials evoked from the viscera, including bladder (Badr et al., 1982), rectum (Collet et al., 1988; Frieling et al., 1989a) and oesophagus (Frieling et al., 1989b; Smout et al., 1990; Tougas et al., 1993) have also been recorded. However, the spatio-temporal distribution of these evoked potentials has not been studied and there- fore the cortical source of these potentials is unknown. Studies of the cortical potentials evoked by proximal and distal oesophageal stimulation in man provide an excellent opportunity for comparing the cortical represen- tation of somatic and visceral afferents. This is because the human oesophagus is composed of 2 distinct regions with different wall structure and neurophysiological character- istics, a proximal, striated muscle, (somatic) component and a distal, smooth muscle, (visceral) component (Chris- 0168-5597/95/$09.50 © 1995 Elsevier Science Ireland Ltd. All rights reserved SSDI 0013-4694(94)00297-5 EEP 94610