title: Modulation of activity in swallowing motor cortex following esophageal acidification: a functional magnetic resonance imaging study.
abstract: Esophageal acid exposure induces sensory and motility changes in the upper gastrointestinal tract; however, the mechanisms involved and the effects on activity in the brain regions that control swallowing are unknown. The aim of this study was to examine functional changes in the cortical swallowing network as a result of esophageal acidification using functional magnetic resonance imaging (fMRI). Seven healthy volunteers (3 female, age range=20-30 years) were randomized to receive either a 0.1 M hydrochloric acid or (control) saline infusion for 30 min into the distal esophagus. Postinfusion, subjects underwent four 8 min blocks of fMRI over 1 h. These alternated between 1 min swallowing water boluses and 1 min rest. Three-dimensional cluster analysis for group brain activation during swallowing was performed together with repeated-measures ANOVA for differences between acid and saline. After acid infusion, swallowing-induced activation was seen predominantly in postcentral gyrus (p<0.004). ANOVA comparison of acid with saline showed a significant relative reduction in activation during swallowing of the precentral gyrus (M1) BA 4 (p<0.008) in response to acid infusion. No areas of increased cortical activation were identified with acid vs. saline during swallowing. Esophageal acidification inhibits motor and association cortical areas during a swallowing task, probably via changes in vagal afferent or nociceptive input from the esophagus. This mechanism may play a protective role, facilitating acid clearance by reduced descending central motor inhibition of enteric/spinal reflexes, or by preventing further ingestion of injurious agents.
authors.affiliation: GI Sciences, University of Manchester, Manchester, UK. peter.paine@manchester.ac.uk
authors.forename: Peter A
authors.initials: PA
authors.lastname: Paine
authors.forename: Shaheen
authors.initials: S
authors.lastname: Hamdy
authors.forename: Xavier
authors.initials: X
authors.lastname: Chitnis
authors.forename: Lloyd J
authors.initials: LJ
authors.lastname: Gregory
authors.forename: Vincent
authors.initials: V
authors.lastname: Giampietro
authors.forename: Mick
authors.initials: M
authors.lastname: Brammer
authors.forename: Steve
authors.initials: S
authors.lastname: Williams
authors.forename: Qasim
authors.initials: Q
authors.lastname: Aziz
mesh_terms: D000328:Adult; D003680:Deglutition Disorders / Q000139:chemically induced* / Q000175:diagnosis* / Q000503:physiopathology; D004947:Esophagus / Q000187:drug effects* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006851:Hydrochloric Acid / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology* / Q000503:physiopathology*; D016037:Single-Blind Method; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D012965:Sodium Chloride; D006851:Hydrochloric Acid