Dynamic changes and spatial correlation of EEG activities during cold pressor test in man

To explore the effects of tonic cold pain in man, the pain rating (intensity and distress), skin temperature, and continuous EEG recording were conducted before, during, and after cold pressor test (CPT) in 15 young healthy males. The acquired electroencephalogram (EEG) data was analysed in four ways: (1) comparison of EEG topographic patterns and power spectra across baseline, CPT, and post-CPT; (2) dynamic EEG changes during CPT; (3) correlation of EEG activities at the isolated focal maxima across the three experimental stages; and (4) spatial correlation of EEG powers among the focal sites during CPT. Compared to baseline, CPT induced significant differences in EEG topographic patterns and power spectra, which showed the following characteristics. (A) The delta and theta activities increased in frontal areas with maxima at F8. (B) The alpha activities decreased in the posterior part of the head with maxima at POz. (C) The beta activities increased in the peripheral bi-temporal regions. (D) The decrease of alpha and increase of beta activities occurred immediately after the onset of CPT, but the increase of delta activity showed a relatively gradual process. (E) Individual consistency was significantly observed in delta power at F8 and alpha-1 power at POz across the stages. (F) Two independent spatial clusters of EEG activation, fronto-temporal delta-theta-beta activities and posterior parietal alpha activities emerged during CPT. This new evidence and the detailed EEG effects in CPT may enhance our understanding of the dynamics in cerebral processing of tonic noxious information. Alpha reduction may reflect the attention processing in nociceptive input, and the delta/theta/beta activation may be related to the motivational modulation of the brain.