New research shows that signals traveling from the stomach to the brain via the vagus nerve help form memories, particularly about food, suggesting that digestion plays an active role in how the brain learns and remembers.
For the study, published in Nature Communications, researchers focused on the vagus nerve, the primary communication link between the digestive system and the brain. In experiments with rats, they found that eating nutritious food triggered neurons connecting to the hippocampus to release more acetylcholine, a neurotransmitter that supports memory encoding. When the researchers severed communication along the vagus nerve, that acetylcholine boost disappeared and the rats performed worse on tasks requiring them to remember where they'd recently found food.
Notably, the effect tracked with nutrition, not taste. Rats that consumed sugar or fat showed strong memory-related brain activity, while those given sweet but calorie-free liquids did not—indicating the brain is responding to a food's actual nutritional value rather than its flavor.
According to the study results, rats fed a chronic high-fat, high-sugar diet early in life showed weaker gut-to-hippocampus communication later on, even after switching back to a healthier diet. Given that obesity, poor diet and metabolic disorders like diabetes are already linked to cognitive decline, the findings offer a possible biological explanation: persistent junk-food exposure may disrupt the gut-brain connection long-term.
The work could also shed new light on neurodegenerative diseases.
“The disruption of acetylcholine signaling in the hippocampus is one of the earliest neurochemical changes in Alzheimer’s disease,” said study author Scott Kanoski, professor of biological sciences at University of Southern California. “By revealing that this system is boosted by gut signaling from the vagus nerve, novel therapeutic targets could leverage this information to explore vagus nerve-based approaches, such as vagus nerve stimulation.”
The discovery also raises the possibility of new treatments to strengthen communication between the gut and the brain. Therapies that stimulate the vagus nerve or improve gut health could potentially help protect memory and cognitive function.
Data from USC