title: Longitudinal change in perceptual and brain activation response to visceral stimuli in irritable bowel syndrome patients.
abstract: OBJECTIVE
  Symptom-related fears and associated hypervigilance toward visceral stimuli may play a role in central pain amplification and irritable bowel syndrome (IBS) pathophysiology. Repeated stimulus exposure leads to decreased salience of threat and reduction of hypervigilance. We sought to evaluate hypervigilance in IBS visceral hypersensitivity and associated brain activity.
  
  
  METHODS
  Twenty IBS patients (14 female; moderate to severe symptoms) and 14 healthy controls participated in symptom and rectal distention assessments 6 times over 12 months. In a subset of 12 IBS patients, H2 15O-positron emission tomography images were obtained during baseline, rectal distentions, and anticipation of an aversive distention during the first and last session. Statistical parametric mapping (SPM99) was used to identify areas and networks activated during each session as well as those with differential activation across the 2 sessions.
  
  
  RESULTS
  Perceptual ratings of the rectal inflations normalized over 12 months, whereas IBS symptom severity did not. There were no sex-related differences in these response patterns. Stable activation of the central pain matrix was observed over 12 months, and activity in limbic, paralimbic, and pontine regions decreased. During the anticipation condition, there were significant decreases in amygdala, dorsal anterior cingulate cortex, and dorsal brainstem activation at 12 months. Covariance analysis supported the hypothesis of changes in an arousal network including limbic, pontine, and cortical areas underlying the decreased perception seen over the multiple stimulations.
  
  
  CONCLUSIONS
  In IBS patients, repeated exposure to experimental aversive visceral stimuli results in the habituation of visceral perception and central arousal, despite stable activation of networks processing visceral pain and its anticipation.
authors.affiliation: Center for Neurovisceral Sciences and Women's Health, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA. nailboff@ucla.edu
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Naliboff
authors.forename: Steve
authors.initials: S
authors.lastname: Berman
authors.forename: Brandall
authors.initials: B
authors.lastname: Suyenobu
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Labus
authors.forename: Lin
authors.initials: L
authors.lastname: Chang
authors.forename: Jean
authors.initials: J
authors.lastname: Stains
authors.forename: Mark A
authors.initials: MA
authors.lastname: Mandelkern
authors.forename: Emeran A
authors.initials: EA
authors.lastname: Mayer
mesh_terms: D015746:Abdominal Pain / Q000209:etiology / Q000503:physiopathology*; D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D001921:Brain / Q000503:physiopathology*; D002404:Catheterization; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D017288:Pain Threshold; D010812:Physical Stimulation; D049268:Positron-Emission Tomography; D012007:Rectum; D012720:Severity of Illness Index; D014781:Viscera / Q000294:innervation* / Q000503:physiopathology