title: Negative expectations facilitate mechanical hyperalgesia after high-frequency electrical stimulation of human skin.
abstract: BACKGROUND
  High-frequency electrical stimulation (HFS) of human skin induces not only an increased pain sensitivity in the conditioning area but also an increased pain sensitivity to mechanical punctate stimuli in the non-conditioned surrounding skin area. The aim of the present study was to investigate whether this heterotopically increased mechanical pain sensitivity can be facilitated through the induction of negative expectations.
  
  
  METHODS
  In two independent conditions [a nocebo (n = 15) and control condition (n = 15)], we applied mechanical pain stimuli before, directly after, 10 min and 20 min after HFS in the skin area surrounding the conditioning area, and measured the reported pain intensity [visual analogue scale (VAS)]. All subjects (of both conditions) received a written instruction about the HFS protocol, but only the instruction in the nocebo condition was extended by the following text (in Dutch): 'After the HFS, your skin will become more sensitive to the pinprick stimulation'.
  
  
  RESULTS
  Our results clearly show that induced expectations of increased mechanical pain sensitivity after HFS facilitates the reported pain intensity after HFS more than when no information is given.
  
  
  CONCLUSIONS
  This study shows for the first time that brain mechanisms, via the induction of negative expectations, can facilitate heterotopic mechanical hyperalgesia after HFS of human skin.
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, The Netherlands.
authors.forename: E N
authors.initials: EN
authors.lastname: van den Broeke
authors.forename: N
authors.initials: N
authors.lastname: Geene
authors.forename: C M
authors.initials: CM
authors.lastname: van Rijn
authors.forename: O H G
authors.initials: OH
authors.lastname: Wilder-Smith
authors.forename: J
authors.initials: J
authors.lastname: Oosterman
mesh_terms: D000293:Adolescent; D000328:Adult; D003213:Conditioning, Psychological; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology; D064786:Nocebo Effect; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D010812:Physical Stimulation; D012718:Set, Psychology; D012867:Skin; D055815:Young Adult