Behavioral/Systems/Cognitive Gamma-Band Oscillations in the Primary Somatosensory Cortex—ADirect and Obligatory Correlate of Subjective

Electroencephalographic gamma band oscillations (GBOs) induced over the human primary somatosensory cortex (SI) by nociceptive stimuli have been hypothesized to reflect cortical processing involved directly in pain perception, because their magnitude correlates with pain intensity. However, as stimuli perceived as more painful are also more salient, an alternative interpretation of this correlation isthatGBOsreflectunspecificstimulus-triggeredattentionalprocessing.Infact, this issuggestedbyrecentobservationsthatotherfeaturesofthe electroencephalographic (EEG) response correlate with pain perception when stimuli are presented in isolation, but not when their saliency is reducedbyrepetition.Here,bydeliveringtrainsof threenociceptivestimuliataconstant1s interval, andusingdifferentenergies toelicitgraded pain intensities, we demonstrate that GBOs recorded over SI always predict the subjective pain intensity, even when saliency is reduced by repetition. These results provide evidence for a close relationship betweenGBOs and the cortical activity subserving pain perception