People tie food to memories all the time. The taste of an ice pop might bring you back to summers as a child. Cinnamon in tea may immediately evoke the holidays. New research has found the memories aren’t just stored in flavor. Signals in the digestive tract may decide what food-related activities become memories, according to researchers from the Univ. of Southern California.
The team, led by Prof. Scott Kanoski, looked at the vagus nerve that travels between the gut and the brain. Researchers knew the nerve influenced eating habits as it plays a role in appetite, digestion and feeling satiated. The new study found the nerve also carries memories in rats.
When rats ate nutrient-rich foods, messages traveled from the gut, through the vagus nerve, to the brain. It triggered increased activity in the hippocampus. The hippocampus is where memory and learning happen in the brain. When communication on the nerve was interrupted, the hippocampus no longer had a boost in activity. The rats also performed worse on memory tests about where they had recently stored foods.
While we think of memories as being tied to food we love, the research found that the memory-boosting abilities of food came from nutrients, not flavor. Rats that ate sugar and fat had strong brain signals for memory. Rats eating low-calorie diets didn’t have the same boost.
"We think the mechanism likely evolved to help animals remember vital information about food sources," said study first author Logan Lauer, a PhD student in Kanoski's lab. Signals from the gut tell the brain, "This meal provided valuable nutrients, so remember where and how you got it."
Remembering where food came from is essential in the wild. It can help animals return to a reliable food source. The gut may remember where the highest-energy foods came from. While fatty and sugary foods produced a strong response in the brain at first, the response dulled over time. The rats had a harder time remembering the location of foods over long periods. It suggests that junk food may harm the gut-brain connection over time.
The researchers said that their research may, in the future, lead to more memory health treatments. Stimulating the vagus nerve could aid digestive health, cognitive function and memory.
However, we will stress that it is essential to remember that the research was done in rats, not humans. Moreover, all the rats were male, so it’s possible that the results would be different for female rats, let alone humans. The research is interesting, but more work is needed to know if it is meaningful to humans.
