Scientists discover how the brain learns to avoid food that made you sick
Many of us have a vivid memory of a time we got food poisoning—and probably haven’t touched that food since.
Now, scientists at Princeton University have discovered how the brain creates such strong memories from just one bad experience.
Their study, recently published in Nature, could also help us understand how traumatic memories form in other situations, like in post-traumatic stress disorder (PTSD).
The research was led by Dr. Christopher Zimmerman, a neuroscientist at the Princeton Neuroscience Institute, along with professor Ilana Witten.
They were interested in how the brain links a specific food to an illness, especially since the sickness usually comes hours after the meal. This delay—what Zimmerman calls the “meal-to-malaise” gap—has long been a mystery.
To study this, the team worked with mice. First, the mice were given a new drink they had never tasted before: grape Kool-Aid. The mice learned that poking their nose in a certain spot would give them a small drop of the drink. Then, 30 minutes later, the researchers gave them an injection that made them feel temporarily sick—mimicking food poisoning.
Two days later, when given a choice between water and Kool-Aid, the mice avoided the Kool-Aid entirely. This showed they had formed a strong memory linking the drink to feeling unwell. But what surprised the researchers was which part of the brain was responsible: the central amygdala.
The central amygdala is a small region deep in the brain that plays a key role in emotions like fear and anxiety.
It also processes information from the senses, like smell and taste. The team found that this part of the brain was active when the mice drank the Kool-Aid, when they felt sick, and again when they remembered the experience days later.
Zimmerman and Witten were excited to discover that this area was involved in every stage of memory formation.
They also traced how the feeling of sickness reached the brain. Signals from the gut were sent to the central amygdala through special nerve cells in the lower brain that carry a protein called CGRP. When researchers activated these cells—without causing real illness—the mice still avoided the Kool-Aid.
Even more fascinating, the same brain cells that responded to the Kool-Aid during the first tasting were reactivated when the mice felt sick.
It was as if the brain was replaying the memory to figure out what caused the illness.
This research shows how the brain can connect events that happen hours apart, helping us learn from experience.
The findings may one day help scientists understand how strong negative memories are formed—and possibly how to treat conditions like PTSD.
If you care about nutrition, please read studies about the power of beetroot juice, and the risks of mixing medications with dietary supplements.
For more health information, please see recent studies about how to boost iron intake: natural solutions for anemia, and results showing vitamin K may lower your heart disease risk by a third.
