title: Effects of insular stimulation on thermal nociception.
abstract: BACKGROUND
  Electrical stimulation used for brain mapping in the postero-superior insula can evoke pain. The effects of prolonged high frequency insular stimulation on pain thresholds are unknown.
  
  
  OBJECTIVE
  Prolonged high frequency insular stimulation, by virtue of its inhibitory properties on networks, could decrease thermal nociception.
  
  
  METHODS
  Epileptic subjects had electrodes implanted in the insular cortex for the purpose of epileptic focus resection. Thermal and pressure nociceptive thresholds were tested bilaterally on the forearm on two consecutive days. Randomly assigned double-blind high frequency (150 Hz) insular stimulation took place for 10 min before pain testing either on the first day or on the second day.
  
  
  RESULTS
  Six subjects (three females; mean age of 35 years) were included. Insular stimulation increased heat pain threshold on the ipsilateral (p = 0.003; n = 6) and contralateral sides (p = 0.047; n = 6). Differences in cold pain threshold did not reach statistical significance (ipsilateral: p = 0.341, contralateral: p = 0.143; n = 6), but one subject had a profound decrease in both heat and cold pain responses. Pressure pain threshold was not modified by insular stimulation (ipsilateral: p = 0.1123; contralateral: p = 0.1192; n = 6). Two of the three subjects who had a postero-superior operculo-insulectomy developed central pain with contralateral thermal nociceptive deficit.
  
  
  CONCLUSIONS
  High frequency inhibitory postero-superior insular stimulation may have the potential to decrease thermal nociception. Together with previous studies, our data support the notion that the integrity of this brain region is necessary for thermal but not pressure nociceptive processing.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Centre Hospitalier de l'Université de Montréal (Hôpital Notre-Dame), Canada.
authors.forename: D J
authors.initials: DJ
authors.lastname: Denis
authors.affiliation: Department of Neuroscience, Université de Montréal, Canada.|Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM), Université de Montréal, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Marouf
authors.affiliation: Department of Neuroscience, Université de Montréal, Canada.|Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM), Université de Montréal, Canada.|Department of Stomatology, Université de Montréal, Canada.|Centre de recherche en neuropsychologie et cognition (CERNEC), Université de Montréal, Canada.|Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Rainville
authors.affiliation: Division of Neurosurgery, Department of Surgery, Centre Hospitalier de l'Université de Montréal (Hôpital Notre-Dame), Canada.
authors.forename: A
authors.initials: A
authors.lastname: Bouthillier
authors.affiliation: Department of Neuroscience, Université de Montréal, Canada.|Division of Neurology, Department of Medicine, Centre Hospitalier Université de Montréal (Hôpital Notre-Dame), Canada.
authors.forename: D K
authors.initials: DK
authors.lastname: Nguyen
mesh_terms: D000328:Adult; D001921:Brain; D001931:Brain Mapping; D002540:Cerebral Cortex; D003080:Cold Temperature; D004311:Double-Blind Method; D004558:Electric Stimulation; D000069280:Electrocorticography; D004827:Epilepsy / Q000503:physiopathology; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D059225:Nociception; D010146:Pain; D017288:Pain Threshold; D011312:Pressure