A nerve connecting the stomach to the head is a conduit determining how people recall the past, a team of United States-based scientists has found.
This research could help explain not only how memory functions, but also how diet affects the development of diseases such as Alzheimer’s.
The University of Southern California (USC) researchers discovered evidence that the vagus nerve, which has long been know to control digestion and hunger pangs, carries signals from the gut to the hippocampus.
This is “a part of the brain critical for learning and memory”, according to the team.
In a study based on tests on rats and published in the journal Nature Communications, the USC team say that eating spurs the release of a neurotransmitter chemical called acetylcholine, which the body uses to help the brain “encode new experiences”.
In turn, the researchers found that disrupting vagus nerve communications caused the spike in the chemical to reverse.
“We think the mechanism likely evolved to help animals remember vital information about food sources,” says study first author and PhD candidate Logan Lauer.
This theory came about after the team found indications that the response was triggered not only by taste, but also by the nutritional value of the food.
“Rats who ate sugar or fat showed strong memory-related brain activity,” the researchers say, pointing out that animals served “sweet-tasting, but low-calorie” alternatives “did not show the same response”.
At the same time, the findings came with a warning, as “chronic exposure” to the same high-fat, high-calorie items diminished memory formation over the long term and adds to evidence that a junk diet does not just make a person fat, but can also contribute to brain degeneration.
“Scientists already know that obesity, poor diet and metabolic disorders such as diabetes are associated with cognitive decline,” the team says, explaining that their research adds to evidence that junk food “may disrupt or disturb the connection between our gut and our brain”.
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“The disruption of acetylcholine signalling in the hippocampus is one of the earliest neurochemical changes in Alzheimer’s disease,” study senior author and professor of biological sciences Dr Scott Kanoski says.
“By revealing that this system is boosted by gut signalling from the vagus nerve, novel therapeutic targets could leverage this information to explore vagus nerve-based approaches, such as vagus nerve stimulation,” he adds. – dpa
