Topology of EEG coherence changes may reflect differential neural network activation in cold and pain perception

Pain perception in the brain can be analyzed by neuroimaging (PET, fMRI) an d electrophysiological parameter mapping (EEG, ERP/MEG, MEF). These studies have generally been focused on the localization of cerebral activation. Wh ether pain can be conceptualized as localized function or best be understoo d by distributed function is important to the theory of human pain processi ng in the brain. Here, we report that cold and pain perception in the brain is characterized by webs of EEG coherence changes which may reflect coupli ng or de-coupling of different cortical areas during cold and pain processi ng. EEG was recorded during cold and pain perception (right hand immersion in 15 degrees C cool-water vs. 0.3 degrees C ice-water for 3 min.) with eye s opened. Subjects rated the cold perception at 2.3 (cool to cold, but no p ain) and the pain perception at 6.7 (moderate-strong pain) in a 1-10 scale. The obtained EEG spectral parameters were compared with the corresponding parameters of the resting baseline using paired Wilcoxon tests in the sense of statistical filters to depict those differences which differ clearly fr om changes by chance. The results were presented in probability maps. The E EG results indicated highly differential coherence networks between cold an d pain perception. The cold perception was characterized as decreased coher ence in the theta band mainly between frontal electrodes and increased inte rhemispheric coherence in the alpha range mainly between central and fronta l positions. During pain perception almost no coherence changes in the thet a band were observed, but great coherence increase in the delta band betwee n central, parietal and frontal electrodes. The network of coherence change s in the alpha band showed strong involvement of electrode C3 concerning co herence increases with frontal positions. In the beta-1 band coherence incr ease within the left hemisphere was much more pronounced during pain than d uring cold. The differential characteristics of EEG coherence changes based on neural networks and their spatial organization in the neocortex indicat e the distributed brain processing between cold and pain perception in man. This study may contribute to our understanding of the large scale neural n etworks in cognition based on neurophysiological binding hypothesis and net work connections of neural ensembles.