How Gut Hormones Manipulate the Brain's Decision Process

A hormone released in the gut when an organism feels hungry has a direct connection with the brain's hippocampus, affecting food-related decision-making, according to scientific findings. The research, conducted on mice, revealed that the hunger hormone influences brain activity, either inhibiting or promoting eating based on the hunger level of the creature under study.

Researchers discovered that these hunger hormones located in the gut have a direct impact on the hippocampus, a region of the brain. This impact appears to influence decisions about eating. Through a study conducted on mice, researchers illustrated how the brain restricts eating when hunger signals decrease. This would give insight into the understanding and treatment of eating disorders.

A study by UCL (University College London) researchers contributed further to this knowledge, noting that a hunger hormone produced in the gut can directly influence a decision-making region of the brain, modifying an animal’s behavior.

Published in the journal Neuron, the study is the first of its kind showing the consequence of hunger hormones on the activity of the hippocampus during decision-making about food.

Dr. Andrew MacAskill (UCL Neuroscience, Physiology & Pharmacology), the study's lead author, stated: “The concepts of hunger and fullness can be a great influence on our decisions. For example, your buying habits at a grocery store may differ depending on whether you are full or hungry. However, this seemingly simple concept requires the ability to use ‘contextual learning’ in reality.

MacAskill added,"We found that a crucial part of the brain for decision-making is particularly susceptible to levels of hunger hormones produced in the gut, which we believe aids our brains in contextualizing our dietary decisions."

The research displayed real-time images of mice brains as they navigated an arena with food when hungry or full, showing certain neural activity patterns. Hungry mice showed significantly less activity in these brain regions than their satiated counterparts.

The areas of focus were specific brain cells in the ventral hippocampus (underneath the hippocampus), a region known to play a significant role in behavioral guidance using memories.

The study found that when animals approached food, activity increased in a segment of brain cells in the ventral hippocampus, restraining the animals from eating. If the mouse was hungry, however, this brain region's activity declined, and the animal started eating.

In a key development, UCL researchers could prompt mice to act as if they were full by stimulating these ventral hippocampal neurons, which caused the animals to stop eating despite their hunger. They obtained similar results by removing ghrelin receptors from these neurons.

Previous studies have found ghrelin receptors in the hippocampi of numerous species, including non-human primates, but the functions of these receptors remained unproven.

This research has provided insight into the usage of ghrelin receptors in the brain. The hunger hormone can enter the brain and directly affect neural activity, controlling a likely similar circuit in the human brain.

The investigators are further exploring whether hunger can influence learning or memory. They are assessing if hunger alters how mice perform tasks unrelated to food. Further research could also illuminate whether similar mechanisms operate when experiencing stress or thirst.

Dr. Ryan Wee (UCL Neuroscience, Physiology & Pharmacology), the study's first author, commented: “If any discrepancies occur in decision-making based on our hunger levels, it could lead to severe health issues. We aim to enhance our understanding of these brain processes, potentially helping prevent and treat eating disorders."