Pain-specific gamma-band oscillations recorded from the human insula

Abstract

Introduction. Pain is a multi-dimensional experience, including sensory, affective, and cognitive components. How these different dimensions integrate into a unified and coherent percept remains an open question. Gamma-band oscillations (GBOs, 30-100 Hz) could represent a possible mechanism to integrate low-level cortical processing of basic stimulus features with high-level cognitive processes. In the present study, we used direct intracerebral recordings performed in humans to investigate whether nociceptive stimulation elicits nociceptive-specific GBOs in the insula, a region considered to play a major role in pain perception. Methods. Intracerebral activity was recorded from a total of 60 insular sites in 5 patients with deep multicontact electrodes, implanted for the presurgical evaluation of focal epilepsy. Patients received stimulation from four sensory modalities: thermonociceptive, tactile, auditory, and visual. Participants were instructed to rate the intensity of each stimulus on a numerical scale ranging from 0 to 10. Results. There was no significant difference in ratings of intensity across modalities. In 4/5 patients, nociceptive stimuli consistently elicited a clear enhancement of GBO power at insular contacts, peaking 245 ms ± 12 ms after stimulus onset (Fig. 1), but not at other intracerebral contacts. Vibrotactile, auditory, and visual stimuli did not elicit such high frequency responses at any of the recorded contacts. Conclusion. Nociceptive stimuli elicit consistent GBOs in the human insula. Because non-nociceptive stimuli do not elicit a similar response, these high frequency oscillations could reflect activity specific for nociception, possibly involved in the integration of stimulus-driven and top-down determinants of pain perception