Analysis Parameters for Objective Assessment of Persistent Pain by EEG

Pain is an indicator of various diseases and injuries, and research has been conducted to objectively evaluate this pain using magnetoencephalography, fMRI, and electroencephalography (EEG). This paper focuses particularly on EEG, which can be evaluated simply. Previous studies on pain have simulated brief stimulation with heat or pulsed electric current, but in this research, sustained pain was inflicted on research subjects using foot pressure point stimulation, which is used for health purposes. The measured data of the somatosensory cortex EEG at that time was analyzed by RMS of the waveform and Hjorth parameters used in real-time signal frequency analysis. The results of the linear mixed-effects model showed that the Activity values of the RMS and Hjorth parameters showed significant regression with stimulus intensity and subjective evaluation, indicating the possibility of objective evaluation of persistent pain using EEG. In addition, the Mobility and Complexity of Hjorth parameters showed no relationship with stimulus intensity, suggesting that the change in EEG frequency due to pain may be non-stationary. Finally, the temporal coefficient of variation of RMS was smaller than that of Activity, suggesting that RMS provides the most stable objective evaluation.