When French writer Marcel Proust famously recalled his childhood from the taste of a Madeline cookie, his stomach may have done some of the work. 

We generally associate our memories almost exclusively with the brain, which we imagine both forms and stores them. New research led by Scott Kanoski, professor of biological sciences at the USC Dornsife College of Letters, Arts and Sciences, has found that our gut may also play an important role in helping us to remember experiences, especially those revolving around food. 

The study, published in Nature Communications, focused on the vagus nerve, a major communication highway that connects the digestive system to the brain. Scientists have long known that the vagus nerve helps regulate digestion, hunger and feelings of fullness. Now, researchers have uncovered evidence that signals traveling from the gut through the vagus nerve can also help to form memories.

Memorable munchies

The researchers found that when rats consumed nutritious foods, neurons communicating to the hippocampus, a part of the brain critical for learning and memory, released higher levels of a chemical called acetylcholine. This neurotransmitter supports memory formation and helps the brain encode new experiences. 

The response depends on signals traveling from the gut via the vagus nerve. When the researchers interrupted vagus nerve communication, the increase in acetylcholine disappeared. These rats also performed worse on memory tests that required them to remember where they had recently found food.

The scientists also discovered that the brain's memory system seems to respond primarily to a food's nutrients, not just its pleasing taste. Rats who ate sugar or fat showed strong memory-related brain activity. Those given sweet-tasting but low-calorie or non-caloric liquids did not show the same response. This suggests that the brain reacts to the actual nutritional value of food, rather than just its flavor.

"We think the mechanism likely evolved to help animals remember vital information about food sources," says study first author Logan Lauer, a PhD student in Kanoski's lab. Recalling where certain plants sprout first in the spring can help hungry animals find important nutrients. Signals from the gut tell the brain, "This meal provided valuable nutrients, so remember where and how you got it."

Brain-boosting research

Although high-fat and high-sugar foods sparked strong memory responses, the study also found that chronic exposure to these items worsened memory formation over time. 

Rats that consumed this type of diet early in life showed weaker communication between the gut and the hippocampus later on. Even after returning to a healthier diet, these animals had reduced memory-related brain responses and poorer performance on food-location memory tasks. 

The findings could have important implications for human health. Scientists already know that obesity, poor diet and metabolic disorders such as diabetes are associated with cognitive decline. This new research suggests one reason why: Constant exposure to junk foods may disrupt or disturb the connection between our gut and our brain. 

Their 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. 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."

Scott Kanoski, professor of biological sciences, USC Dornsife College of Letters, Arts and Sciences

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. 

While much more research is needed to determine whether the same mechanisms operate in humans, the findings add to a growing body of evidence that the gut and brain are deeply connected.

About the study

In addition to Kanoski and Lauer, study authors include Anna Hayes, Andrea Suarez, Alexander Bashaw, Molly Klug, Alicia Kao, Robert Cheng, Jessica Rea, Keshav Subramanian, Anna Nourbash, Kristen Donohue, and Lindsey Schier of USC Dornsife; Kevin Myers of Bucknell University; and Léa Décarie-Spain of Université de Montréal.

This work was supported by National Institute of Diabetes and Digestive and Kidney Diseases grants DK104897, DK123423, F31AG092136; Postdoctoral Ruth L. Kirschstein National Research Service Award from the National Institute on Aging grant F32AG077932; Quebec Research Funds postdoctoral fellowship 315201; and an Alzheimer's Association Research Fellowship to Promote Diversity.

Source:

Journal reference:

Tierno Lauer, L., et al. (2026). The vagus nerve promotes memory in rats via nutrient-induced septo-hippocampal acetylcholine signaling. Nature Communications. DOI: 10.1038/s41467-026-73896-2. https://www.nature.com/articles/s41467-026-73896-2