Transcript Slide 1
Early involvement of right operculo-insular cortex in processing pain unpleasantness: evidence from laser evoked potentials 139784 488-P94 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 N300-T7 and -FCz sub-groups LEPs, global field power (GFP) and scalp topography 10 Amplitude (µV) Right (ipsilateral) operculo-insular -9 -4 -3 -2 -1 0 1 2 Left (contra) operculo-insular -8 -6 FCz T8 Electrode -4 -3 -2 T7 FCz T8 Electrode 6 GFP peaks: 308 and 470 ms 4 2 0 -500 0 500 1000 1500 FCz Latency (ms) T7 Cz T7 Pz -10 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. Amplitude (µV) -5 -500 0 500 1000 1500 0 Latency (ms) 5 10 Source analysis 15 N300 20 FCz 5 500 1000 Amplitude (µV) Amplitude (µV) 0 1500 0 Latency (ms) 5 10 4 0 0 Latency (ms) 430-440 ms 10 15 30 100 200 300 400 500 600 Ipsilateral (right) 10 0 -10 -20 -30 P600-800 (P3e) Amplitude (µV) -5 500 1000 1500 600-800 ms 0 5 0 Control Loc Unpl Unpl. > Control FCz group P<0.05 T7 group Control Loc Unpl 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. Latency (ms) 10 50 0 Greater activity in right operculo-insular cortex during Unpleasantness task suggests early processing of affective component of pain in this area. -50 -100 -150 -200 15 P800-1000 20 (P3l) Acknowledgements 60 800-1000 ms Source activity (nAm) Pz Source activity (nAm) 100 0 10 0 700 20 20 -500 20 10 40 1500 Source activity (nAm) Amplitude (µV) 1000 0 -10 30 20 Contralateral (left) P450 -5 5 40 30 Latency (ms) -10 500 50 40 Conclusions 1 Cz 0 60 50 2 15 -500 60 3 20 • 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. 70 Control task n=21 GFP 290-300 ms -5 -500 70 -5 0 T7 Right (ipsi) operculo-insular -7 -1 3 8 -10 Methods N300-FCz sub-group -10 -5 LEPs (n=21) Control task GFP N300-T7 sub-group -6 Task and sub-group differences in operculo-insular source activities Source activity (nAm) • Pain has sensory-discriminative, affectivemotivational & 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). Mean amplitude (µV) Results Mean amplitude (µV) Introduction 40 20 0 -20 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). Latency (ms) 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). 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.