title: Effects of preceding stimulation on brain activation in response to colonic distention in humans.
abstract: OBJECTIVE
  It has been suggested that the pattern of distension (moderate following mild and vice versa) might influence brain activation and the experience of hypersensitivity, offset analgesia, and anticipation. Nevertheless, how the pattern of stimulation affects sensitization and/or desensitization to visceral stimulation remains unknown.
  
  
  METHODS
  In 45 nonclinical healthy participants (12 women, 33 men; 20-26 years old), brain processing of visceral sensation induced by colonic distension was examined using H2(15)O positron emission tomography. Subjective feelings regarding the stimuli were also measured. The descending colon was stimulated using six patterns of three bag pressures (0, 20, and 40 mm Hg). To evaluate the neural sensitization to visceral stimulation arising from the precedence effect, the effects of a 20- or 40-mm Hg distention after a sham or 20- or 40-mm Hg distension were analyzed using statistical parametric mapping. The level of significance was set at a voxelwise level of p < .0001, with cluster extent sizes of k > 50.
  
  
  RESULTS
  The midbrain, insula, and cerebellum, were more strongly activated by a 20-mm Hg distension with a preceding 40-mm Hg distention than by a 20-mm Hg distention without a preceding stimulation (p < .0001). Conversely, a sham stimulation after the experience of an intense stimulation activated the midcingulate cortex, compared with a sham stimulation without the experience of actual visceral stimulation (p < .0001).
  
  
  CONCLUSIONS
  By directly comparing different patterns of visceral stimuli, preceding visceral stimuli may affect neural sensitization and/or desensitization in humans, including elevated midbrain, insula, and midcingulate cortex.
authors.affiliation: Department of Behavioral Medicine, Graduate School of Medicine, Tohoku University, Aoba, Sendai, Japan.
authors.forename: Toyohiro
authors.initials: T
authors.lastname: Hamaguchi
authors.forename: Michiko
authors.initials: M
authors.lastname: Kano
authors.forename: Motoyori
authors.initials: M
authors.lastname: Kanazawa
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Itoh
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yanai
authors.forename: Shin
authors.initials: S
authors.lastname: Fukudo
mesh_terms: D000328:Adult; D059031:Anticipation, Psychological / Q000502:physiology*; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D059333:Central Nervous System Sensitization / Q000502:physiology*; D003106:Colon / Q000294:innervation / Q000502:physiology*; D004644:Emotions; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000503:physiopathology; D043183:Irritable Bowel Syndrome / Q000503:physiopathology; D008297:Male; D015233:Models, Statistical; D058748:Pain Perception / Q000502:physiology; D010812:Physical Stimulation / Q000379:methods; D049268:Positron-Emission Tomography; D011312:Pressure; D012039:Regional Blood Flow; D012677:Sensation / Q000502:physiology; D014781:Viscera / Q000294:innervation / Q000502:physiology; D055815:Young Adult
keywords: brain-gut interaction; emotion; hyperalgesia; visceral perception; visceral sensitization