title: Quantitative meta-analysis identifies brain regions activated during rectal distension in irritable bowel syndrome.
abstract: OBJECTIVE
  The responsiveness of the central nervous system is altered in patients with irritable bowel syndrome (IBS). However, because of variations in experimental paradigms, analytic techniques, and reporting practices, little consensus exists on brain responses to visceral stimulation. We aimed to identify brain regions consistently activated by supraliminal rectal stimulation in IBS patients and healthy subjects (controls) by performing a quantitative meta-analysis of published studies.
  
  
  METHODS
  Significant foci from within-group statistical parametric maps were extracted from published neuroimaging studies that employed rectal distension. Voxel-based activation likelihood estimation was applied, pooling the results and comparing them across groups.
  
  
  RESULTS
  Across studies, there was consistent activation in regions associated with visceral afferent processing (ie, thalamus, insula, anterior midcingulate) among IBS patients and controls, but considerable differences in the extent and specific location of foci. IBS patients differed from controls in that there were more consistent activations in regions associated with emotional arousal (pregenual anterior cingulate cortex, amygdala) and activation of a midbrain cluster, a region playing a role in endogenous pain modulation. Controls showed more consistent activation of the medial and lateral prefrontal cortex.
  
  
  CONCLUSIONS
  Patients with IBS have greater engagement of regions associated with emotional arousal and endogenous pain modulation, but similar activation of regions involved in processing of visceral afferent information. Controls have greater engagement of cognitive modulatory regions. These results support a role for central nervous system dysregulation in IBS. These findings provide specific targets for guiding development of future neuroimaging protocols to more clearly define altered brain-gut interactions in IBS.
authors.affiliation: Center for Neurobiology of Stress, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Tillisch
authors.forename: Emeran A
authors.initials: EA
authors.lastname: Mayer
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Labus
mesh_terms: D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000503:physiopathology*; D008297:Male; D015233:Models, Statistical; D010146:Pain / Q000503:physiopathology; D012007:Rectum / Q000294:innervation*