Influence of gut-brain signals on psychobiological processes in healthy humans

The bidirectional neural and hormonal communication system between the brain and the gastrointestinal tract, known as the ‘brain-gut axis’ (BGA), is part of an integrated interoceptive system that continuously conveys homeostatic information about the physiological state of the body to the brain. The homeostatic information is integrated with exteroceptive and interoceptive signals, input from the brain reward system, and affective and cognitive brain circuits, and may therefore influence higher brain functions.

The overall objective of this doctorate project was to study the influence of (subliminal) gut-brain signals on psychobiological functions in healthy humans. A series of proof-of-concept studies were performed to test such influence of different gut-brain signals, using a combination of behavioral paradigms as well as neural and endocrine measurements.

Specifically, this project aimed to investigate the interaction between subliminal nutrient signaling and subjective responses to positive emotion, to investigate whether fatty acid-induced gut-brain signaling interacts with reward sensitivity in different domains, to examine whether nutrients enhance executive control via purely interoceptive gut-brain pathways, to explore the neural basis of the already established effect of the motilin agonist erythromycin infusion on hunger feelings, and to investigate whether cognitive control would be enhanced under conditions of defecatory urge induced by rectal balloon distension.

Although not all hypotheses were confirmed, we provided proof of concept that (subliminal) gut-brain signaling has the potential to affect various psychobiological functions and identified some of the underlying endocrine and neural mechanisms.