EEG coherence changes may reflect neural network activation during cold and pain perception

ABSTRACTS

EEG Coherence Changes May Reflect Neural Network Activation during Cold and Pain Perception Andrew C.N. Chen*, Anthony K.P. Jones*, Peter Rappelsberger** * Human Physiology and Pain Research Laboratory Hope Hospital, Manchester Univ. School of Medicine Salford, M6-SHD, UK (email: achen@fsl, ho.man.ac, uk) ** Institute of Neurophysiology, University of Vienna Waehringerst. 17, A ] 090 Vienna, Austria {Study Aims} In our previous report on the topographic mapping of human pain (Chen, Human Brain Mapping, suppl. 1: p. 183), we described the temporo-spatial evoked potentials using a noxious laser stimulation and the spatial coherence of EEG bands to painful cold pressor test., Current studies have been focused on the localization of cerebral activation. Whether pain can be conceptualized as localized function or best be understood by distributed function is important to the theory of human pain processing in the brain. In this study, we report that cold and pain perception in the brain is characterized by webs of EEG coherence changes reflecting coupling or decoupling of different cortical areas during cold and pain processing. {Methods} 10 healthy male subjects participated as volunteers. 19 channels EEG were recorded according to the 10-20 system. Averaged power spectra and cross-power spectra between all possible electrode pairs (171 in total) were computed for six EEG frequency bands: delta, theta, alpha-l, alpha-2, alpha, beta-1. Coherence and mean amplitude per frequency band was computed. EEG was recorded with eyes closed during cold perception (right hand immersed in a 15~ cold water for 3 min.) and pain perception (0.3~ ice-water for 3 rain.). The perceived intensity was rated in a l(barely cool, no pain) to 10 (excruciating pain) scale. The obtained EEG spectral parameters were compared with baseline activity with eyes closed at rest. The results of statistical evaluations (paired Wilcoxon tests) were presented in probability maps, {Results} Subjects rated the cold perception at 2.3 (cool to cold, but no pain) and the pain perception at 6.7 (moderate-strong pain). The EEG results indicated different coherence networks between cold and pain perception. The cold perception was characterized as decreased coherences in delta and theta bands in the frontal regions and increased coherences in alpha and beta-1 bands mainly in the centro-parietal regions. In contrast, pain perception showed almost no coherence changes in the theta band, but coherence increase in delta activity between central, parietal and frontal areas. The network of coherence changes in the alpha bands was similar in both situations, and the beta-1 band coherence increase in the left hemisphere was much more pronounced during pain than during cold. {Conclusion} The differential characteristics of EEG coherence changes and their spatial organization in the neocortex indicate the distributed brain processing between cold and pain perception in man. This study was supported by the CEC Biomed-I (ANNDEE; BMH1-CT94-1129) $324