Prestimulus theta oscillations and connectivity modulate pain perception

Abstract

The perception of pain is strongly influenced by cognitive processes, such as expectations toward the efficacy of pain medication. It is reasonable to assume that such processes, among other sources of fluctuation, are reflected in ongoing brain activity, which in turn influences perceptual processing. To identify specific prestimulus EEG activity, and connectivity patterns related to subsequent pain perception in humans, we contrasted painful with nonpainful sensations delivered at the individual threshold level determined by the psychophysical QUEST estimation method (Watson and Pelli, 1983). The 64-channel EEG was recorded using active electrodes during a constant stimulation procedure. The power contrast between trials sorted by rating revealed a signal decrease of8%before stimulus onset in theta-band (4 -7 Hz) at T7/FT7 as well as increased theta-power by 6% at T8/FT8. Gamma-band power was increased (12%, 28 -32 Hz) at frontocentral sites (all p < 0.05). Changes in theta-band power are covarying with subsequent pain perception, as well as lowered frontolateral theta-band connectivity for painful percepts. A decrease in frontoparietal connectivity for painful sensations was also identified in the gamma-band (28-32 Hz). A single-trial logistic regression revealed significant information content in the EEG signal at temporal electrode T7 in theta-band (p < 0.01) and frontal electrode F1 in gamma-band (all p < 0.02). The observed patterns suggest top-down modulation of the theta-band effects by a frontocentral network node. These findings contribute to the understanding of ongoing subjective pain sensitivity, potentially relevant to both clinical diagnostics and pain management.