title: Gut Taste Stimulants Alter Brain Activity in Areas Related to Working Memory: a Pilot Study.
abstract: OBJECTIVE
  Taste perception is one of the most important primary oral reinforcers, driving nutrient and energy intake as well as toxin avoidance. Taste receptors in the gastrointestinal tract might as well impact appetitive or aversive behavior and thus influence learning tasks and a close relation of neural taste processing and working memory networks seems plausible.
  
  
  METHODS
  In the present pilot study, we determined the effects of five taste qualities "bitter" (quinine), "sweet" (glucose), "sour" (citric acid), "salty" (NaCl) and "umami" (monosodium glutamate, MSG) on working memory processing using functional MRI and their effect on plasma insulin and glucose levels. On six separate occasions, subjects received one of the following test substances dissolved in 200 mL tap water via a nasogastric tube (to circumvent the oral cavity): 1) 2g citric acid corresponding to 52 mM, 2) 2g NaCl; 171 mM, 3) 0.017g quinine; 0.26 mM, 4) 1g monosodium glutamate; 30 mM, 5) 25g glucose; 694 mM and 6) 200 mL tap water (placebo).
  
  
  RESULTS
  The taste qualities "bitter" and "umami" significantly altered brain activation patterns in the primary gustatory cortex as well as in subcortical structures, previously reported to be involved in emotional learning and memory. In contrast, glucose did not reveal any statistically significant brain activation difference. Working memory performance was not different over the six treatments. Plasma insulin and glucose levels were not affected by the different taste substances (MSG, quinine, NaCl and citric acid).
  
  
  CONCLUSIONS
  in this pilot trial, we demonstrate that acute intragastric administration of different taste substances does not affect working memory performance in humans. However, "umami" and "bitter" have effects on brain areas involved in neural working memory, overpowering the effects of "sweet", "salty" and "sour" reception.
authors.affiliation: Department of Biomedicine, Division of Gastroenterology, University Hospital Basel, Basel, Switzerland.
authors.forename: Anne Christin
authors.initials: AC
authors.lastname: Meyer-Gerspach
authors.forename: Claudia
authors.initials: C
authors.lastname: Suenderhauf
authors.forename: Lukas
authors.initials: L
authors.lastname: Bereiter
authors.forename: Davide
authors.initials: D
authors.lastname: Zanchi
authors.forename: Christoph
authors.initials: C
authors.lastname: Beglinger
authors.forename: Stefan
authors.initials: S
authors.lastname: Borgwardt
authors.forename: Bettina K
authors.initials: BK
authors.lastname: Wölnerhanssen
keywords: Bitter taste; Functional MRI; Gut taste receptors; Monosodium glutamate; Quinine; Umami taste; Working memory