Memory formation may not be the brain's job alone. A study led by Scott Kanoski, professor of biological sciences at the USC Dornsife College of Letters, Arts and Sciences, and published in Nature Communications, found that signals traveling from the digestive system to the brain along the vagus nerve contribute to forming memories - particularly memories tied to food.
The vagus nerve is the main communication line between gut and brain, and researchers have long understood its role in digestion, hunger and satiety. Kanoski's team looked at what else those signals do once they arrive. In rats that ate nutritious food, neurons projecting to the hippocampus - the brain region central to learning and memory - released higher levels of acetylcholine, a neurotransmitter that supports memory formation and helps encode new experiences.
That link matters because acetylcholine signaling in the hippocampus is one of the systems that falters in Alzheimer's disease. If nutrient-related signals from the gut normally help drive that chemical release, the finding points to a physiological pathway connecting what and how we eat to how well the memory circuitry works - one that had not been mapped in this way before.
The work was done in rats, so its relevance to human memory remains to be established, and the study describes a mechanism rather than a treatment. Still, it gives researchers a specific circuit to follow: gut to vagus nerve to hippocampal acetylcholine, a chain that could eventually be probed for how diet and digestive signaling influence cognition.