title: Ghrelin modulates encoding-related brain function without enhancing memory formation in humans.
abstract: Ghrelin regulates energy homeostasis in various species and enhances memory in rodent models. In humans, the role of ghrelin in cognitive processes has yet to be characterized. Here we show in a double-blind randomized crossover design that acute administration of ghrelin alters encoding-related brain activity, however does not enhance memory formation in humans. Twenty-one healthy young male participants had to memorize food- and non-food-related words presented on a background of a virtual navigational route while undergoing fMRI recordings. After acute ghrelin administration, we observed decreased post-encoding resting state fMRI connectivity between the caudate nucleus and the insula, amygdala, and orbitofrontal cortex. In addition, brain activity related to subsequent memory performance was modulated by ghrelin. On the next day, however, no differences were found in free word recall or cued location-word association recall between conditions; and ghrelin's effects on brain activity or functional connectivity were unrelated to memory performance. Further, ghrelin had no effect on a cognitive test battery comprising tests for working memory, fluid reasoning, creativity, mental speed, and attention. In conclusion, in contrast to studies with animal models, we did not find any evidence for the potential of ghrelin acting as a short-term cognitive enhancer in humans.
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Kunath
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: N C J
authors.initials: NCJ
authors.lastname: Müller
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tonon
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: B N
authors.initials: BN
authors.lastname: Konrad
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Pawlowski
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kopczak
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Elbau
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Uhr
authors.affiliation: Max Planck Institute for Human Development, Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Kühn
authors.affiliation: Charité - Universitätsmedizin Berlin, Department of Psychiatry and Psychotherapy, CBF, Berlin, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Repantis
authors.affiliation: German Institute for Human Nutrition, Potsdam-Rehbrücke, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Ohla
authors.affiliation: Institute for Diabetes and Obesity, Helmholtz Zentrum München, Munich, Germany; Department of Medicine, Technische Universität München, Munich, Germany.
authors.forename: T D
authors.initials: TD
authors.lastname: Müller
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: Fernández
authors.affiliation: Institute for Diabetes and Obesity, Helmholtz Zentrum München, Munich, Germany; Department of Medicine, Technische Universität München, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tschöp
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Czisch
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Steiger
authors.affiliation: Max Planck Institute of Psychiatry, Munich, Germany; Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands. Electronic address: martin.dresler@donders.ru.nl.
authors.forename: M
authors.initials: M
authors.lastname: Dresler
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology*; D003071:Cognition / Q000187:drug effects / Q000502:physiology*; D063132:Connectome / Q000379:methods*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D054439:Ghrelin / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D057567:Memory, Long-Term / Q000187:drug effects / Q000502:physiology*; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology*; D055815:Young Adult
chemical_list: D054439:Ghrelin
keywords: Cognition; Enhancement; Functional connectivity; Ghrelin; Memory; Resting state