ENTRAINMENT OF PAIN-RELATED INSULAR OSCILLATIONS BY INTRACEREBRAL PERIODIC STIMULATION IN HUMANS

Current neurostimulation approaches for chronic pain have yielded mixed outcomes, partly because the neurophysiological mechanisms behind pain-related brain oscillations remain unclear. Furthermore, these approaches are limited by the absence of causal evidence from deep brain structures. Multicontact depth electrodes, implanted in patients undergoing a presurgical evaluation of focal epilepsy, offer a unique opportunity to effectively modulate brain oscillations in specific neural populations through the delivery of direct low-intensity electrical currents on restricted portions of neural tissue. As the stimulation and intracerebral electroencephalographic (iEEG) recordings are performed concomitantly, stimulation effects on oscillatory activity can be detected with high accuracy. Intracerebral Periodic Stimulation (iPS), a technique primarily employed in epileptic patients for clinical purposes, consists of bursts of biphasic squared electrical pulses delivered through implanted electrodes. We aim to test the anti-nociceptive role of iPS by delivering 60-Hz iPS to insular contacts in a double-blind, sham-controlled design, while patients receive thermonociceptive stimuli on the forearm. Our aims are (1) to validate entrainment effects on neural oscillations previously observed in a pilot study, and (2) to understand how this modulation is involved in pain perception. Preliminary results from the first pilot confirm the increase in spectral power at the frequency of stimulation during iPS, consistent with neural entrainment, whose link to pain perception remains to be clarified in further experimental sessions. Finally, this project has the unique potential to uncover the mechanism of iPS on insular pain-related oscillations, and guide the development of personalized, non-invasive neurostimulation approaches for chronic pain treatment.