New Delhi: The way to a person’s heart may be through his stomach, but a new study suggests that the gut influences the brain too. Researchers from the USC Dornsife College of Letters, Arts and Sciences in California have established a gut-brain connection that shows how the food we eat can decide what we remember.
For the study, published in the journal Nature Communications on 4 June, researchers turned to rats, focussing on the functions of the vagus nerve, the bridge between the brain and the digestive system. So far, scientists had known the role of the nerve in regulating digestion, hunger, and feelings of fullness. But the new study concludes that the signals sent through the vagus nerve can also help make memories.
Researchers, led by Scott Kanoski, professor of biological sciences at the USC Dornsife College of Letters, Arts and Sciences, observed that when rats were given nutritious food, it led to an increased secretion of a chemical called acetylcholine in neurons connected to the hippocampus.
Hippocampus is the part of the brain that is critical for learning and memory, while acetylcholine is a neurotransmitter that helps the “brain encode new experiences.”
The role of the vagus nerve is important here. When researchers blocked the transmission of signals through it, the release of acetylcholine also dropped. In addition, the rats also found it difficult to remember their recent source of food.
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Nutrition matters
It was also observed that the brain cannot be fooled by giving the gut tasty but non-nutritious food. The rats who were given goods rich in sugar or fat showed strong memory-related activity in the brain. On the other hand, when they were fed sweet but low-calorie or non-caloric liquids, the brain didn’t react the same way.
“We think the mechanism likely evolved to help animals remember vital information about food sources,” says the study’s first author Logan Lauer, a PhD student in Kanoski’s lab.
The researchers also found that high-fat and high-sugar foods, while triggering good memory activity, can have a negative impact on memory in the long term.
Rats who consumed such diets during the early days of their lives experienced weaker communication between the gut and the hippocampus later.
And even after getting on a healthier diet, these rats showed reduced memory-related brain responses and also struggled in food-location memory tasks.
“The disruption of acetylcholine signaling in the hippocampus is one of the earliest neurochemical changes in Alzheimer’s disease,” said Kanoski. “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.”