Early involvement of right operculo-insular cortex in processing pain

1. Introduction Results N300-T7 and -FCz sub-groups Task and sub-group differences in operculo-insular source activities • Pain has sensory-discriminative, affective-motivational & cognitive-evaluative components (Melzack & Casey, 1968). • The functional brain anatomy underlying these components remains under investigation. • We used source analysis of laser evoked potentials (LEPs) to compare the temporal sequence of brain activation when volunteers selectively attended to either the unpleasantness (affective component) or the localisation (sensory component) of pain, compared to a control task that was matched for generalised attention. • The results of the peak analyses of these data were reported in Bentley et al. (2004). LEPs, global field power (GFP) and scalp topography FCz group T7 group LEPs (n=21) Control task N300-T7 sub-group N300-FCz sub-group The 21 volunteers differed in the scalp distribution of the N300 peak; 10 showed a contralateral maximum at electrode T7 while the other 11 showed a midline maximum at FCz. Unpl. > Control P<0.05 The right (ipsilateral) source was significantly more active during the Unpleasantness rating task than during the Control task across the whole group (strongest for T7 sub-group). There were no task effects on other source activities or peak latencies. Source analysis Methods Conclusions GFP • 21 healthy right-handed volunteers randomly received moderately painful CO2 laser stimuli to 2 adjacent sites on right forearm. Volunteers performed 3 tasks: • Attend to pain location - report pain location (medial/lateral) • Attend to pain unpleasantness - report unpleasantness on 0-10 scale • Control - report whether painful or not • LEPs recorded from 61 electrodes (bandpass: 0.15-70 Hz, A/D rate: 500 Hz). • 4-dipole model of Schlereth et al. (2003) fitted to data using BESA: sources in bilateral operculo-insular cortices, posterior midcingulate and contralateral postcentral gyrus. Greater activity in right operculo-insular cortex during Unpleasantness task suggests early processing of affective component of pain in this area. Acknowledgements LEP data were well-explained by the source model (mean goodness-of-fit = 83.5 ± 7.7%). The sources were activated in the order: contralateral (left) operculo-insular (opi) (blue, 280 ms), ipsilateral (right) opi (red, 288 ms), early cingulate (green, 291 ms), postcentral gyrus (magenta, 297 ms), late cingulate (green, 450 ms). LEPs consisted of 2 main components, N300 (maximal at T7 and FCz) and P450 (maximal at Cz), with some late positivity evident at parietal sites (early & late P3, P3e & P3l). Supported by the Arthritis Research Campaign, Dr Hadwen Trust for Humane Research, Deutsche Forschungsgemeinschaft & Human Sciences Domain of the UK Ministry of Defence Scientific Research Programme. Control task n=21 Left (contra) operculo-insular Right (ipsilateral) operculo-insular Right (ipsi) operculo-insular 70 70 60 60 50 50 40 Source activity (nAm) 40 30 30 20 20 10 10 0 0 Control Loc Unpl Control Loc Unpl Early involvement of right operculo-insular cortex in processing pain unpleasantness: evidence from laser evoked potentials Deborah E. Bentley1, Ulf Baumgärtner2, Alison Watson1, Geoff Barrett3, Bhavna Kulkarni1, Paula D. Youell1, Anthony K. P. Jones1, Rolf-Detlef Treede2 1 Univ. of Manchester Human Pain Research Group, Hope Hospital, Salford, UK; 2 Institute for Physiology & Pathophysiology, Johannes Gutenberg Univ., Mainz, Germany; 3 Human Sciences Team, Defence Science and Technology Laboratory, Fareham, UK 139784 488-P94