Volunteers with high versus low alpha EEG have different pain-EEG relationship: a human experimental study

The alpha rhythm (7.5-12 Hz) is one of the fundamental features of the human EEG which usually has maximum amplitude over occipital regions. It is well recognized that individuals have highly different magnitudes of alpha EEG. This study examined occipital alpha EEG activity during different levels of experimental tonic cuff-pressure pain. The aim was to study the pain reactions and pain-EEG relationship in subjects with high alpha (H(alpha)) and low alpha (L(alpha)) EEG. Tonic experimental cuff-pressure induced pain, and high density EEG (124 channels) were used. The pain-EEG responses for the high alpha (above 600 microV(2) in total alpha power at baseline), and low alpha (below 600 microV(2) in alpha power at baseline) subjects were analyzed. Forty healthy volunteers were included and received tonic pain for 3 min at three intensities (VRS2) intense, but no pain, (VRS4) slight pain, and (VRS6) moderate pain. There were no differences in stimulus intensities to reach the three ratings between the H(alpha) and the L(alpha) groups. The H(alpha) and L(alpha) groups are highly different in alpha1(PO3), alpha1(PO4), alpha1(PO7) and alpha1(PO8) EEG powers. A positive correlation (P = 0.008) between alpha2(PO3) EEG and average subjective pain ratings was specific for the L(alpha) group. The H(alpha) group showed alpha1 desynchronization as pain increased, but no significant correlation between alpha1 EEG powers and average subjective pain ratings. The differences between the L(alpha) and the H(alpha) in alpha EEG powers and the different pain-EEG responses may be related to different degrees of attention, fear of pain and pain related coping strategies.