title: Slow brushing reduces heat pain in humans.
abstract: C-tactile (CT) afferents are unmyelinated low-threshold mechanoreceptors optimized for signalling affective, gentle touch. In three separate psychophysical experiments, we examined the contribution of CT afferents to pain modulation.
  
  
  
  In total, 44 healthy volunteers experienced heat pain and CT optimal (slow brushing) and CT sub-optimal (fast brushing or vibration) stimuli. Three different experimental paradigms were used: Concurrent application of heat pain and tactile (slow brushing or vibration) stimulation; Slow brushing, applied for variable duration and intervals, preceding heat pain; Slow versus fast brushing preceding heat pain.
  
  
  
  Slow brushing was effective in reducing pain, whereas fast brushing or vibration was not. The reduction in pain was significant not only when the CT optimal touch was applied simultaneously with the painful stimulus but also when the two stimuli were separated in time. For subsequent stimulation, the pain reduction was more pronounced for a shorter time interval between brushing and pain. Likewise, the effect was more robust when pain was preceded by a longer duration of brush stimulation. Strong CT-related pain reduction was associated with low anxiety and high calmness scores obtained by a state anxiety questionnaire.
  
  
  
  Slow brushing - optimal for CT activation - is effective in reducing pain from cutaneous heating. The precise mechanisms for the pain relief are as yet unknown but possible mechanisms include inhibition of nociceptive projection neurons at the level of the dorsal horn as well as analgesia through cortical mechanisms.
  
  
  
  Slow brushing stimuli - optimal for activation of C-tactile fibres - can reduce pain from cutaneous heating. No such effect was seen with fast brushing or vibration. These observations indicate the role of C-tactile fibres in pain modulation.
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Liljencrantz
authors.affiliation: VA San Francisco Healthcare System, USA.|University of California San Francisco, USA.
authors.forename: I
authors.initials: I
authors.lastname: Strigo
authors.affiliation: MGH/HST Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, USA.|Department of Psychology, University of Oslo, Norway.
authors.forename: D M
authors.initials: DM
authors.lastname: Ellingsen
authors.affiliation: Department of Neurology, Justus Liebig University, Giessen, Germany.
authors.forename: H H
authors.initials: HH
authors.lastname: Krämer
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sweden.
authors.forename: L C
authors.initials: LC
authors.lastname: Lundblad
authors.affiliation: Center for Social and Affective Neuroscience, Linköping University, Sweden.|School of Medicine, Western Sydney University, NSW, Australia.
authors.forename: S S
authors.initials: SS
authors.lastname: Nagi
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sweden.|Department of Psychology, University of Oslo, Norway.
authors.forename: S
authors.initials: S
authors.lastname: Leknes
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sweden.|Center for Social and Affective Neuroscience, Linköping University, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Olausson
mesh_terms: D004644:Emotions; D006358:Hot Temperature; D006801:Humans; D008465:Mechanoreceptors / Q000502:physiology*; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D010146:Pain; D010147:Pain Measurement; D011601:Psychophysics / Q000379:methods*; D012867:Skin; D014110:Touch; D014732:Vibration