Electroencephalographic reactions during experimental superficial and deep pain stimuli in awake healthy subjects

Objectives: Electroencephalographic [EEG] abnormalities have been observed during sleep in patients with musculoskeletal disorders, and correspondingly nighttime EEG alterations can be evoked in healthy subjects during experimental pain stimuli. In order to further investigate the cerebral processing to pain, the current experiment was conducted to study the changes in the awake background EEG during superficial and deep pain stimulation. Methods: Well-defined experimental phasic and tonic pain stimuli were applied to the skin, joints and muscles in 10 healthy subjects. The EEG was sampled from nine surface recordings an the scalp before and during the stimuli and frequency analysis was performed. Results: Significant topographical differences were seen during pain for the nine channels. A decrease of power in the alpha 1 band [8-10 Hz] was seen during the cutaneous and joint stimuli, most pronounced in the posterior derivations. During the muscle stimulus no consistent changes were seen in the EEG. Conclusion: The decrease of power in the alpha 1 band may reflect a change in the EEG in response to cutaneous pain. Different mechanisms may be activated in the processing of pain in deep and superficial structures. Such findings may be important in the study of pain in patients with musculoskeletal disorders.