When it comes to walking from the bed to the refrigerator at night in the dark and with half-closed eyes, we seem to have an incredible ‘sixth sense’ which guide us... No need to think, our instincts lead us straight to our destination, allowing us to satisfy our nightly cravings.
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As miraculous as it may seem, there is nothing supernatural about this sudden improvement in our sense of direction. Rather, it is linked to the ‘second brain’ or ‘enteric nervous system’ that is hidden in our innards, as revealed in a study published in Nature Communications in 2018 and conducted by researchers at the University of Southern California (USA).
A very first GPS inherited from our ancestors
In fact, according to scientists, this ‘brain-intestine axis’ sends signals directly to the memory centre of our brain: the hippocampus. These messages then help us to remember the places where we usually find food with extreme precision.
This is an ancestral ability no doubt inherited from our distant hunter-gatherer ancestors, as one of the co-authors of the work, Scott Kanoski, a lecturer in biological sciences at the University of Southern California, explained in a press release:
Especially in those days, it was essential for the digestive system to work in collaboration with the brain like a navigation application such as Waze or Google Maps.
Our distant ancestors certainly had a vested interest in remembering the places richest in food with great accuracy, as an essential survival strategy.
A disconnection of the axis with heavy consequences
To reach their surprising conclusions, the researchers conducted a series of experiments on laboratory rats. Some of them had had the intestine-brain axis that passes through their vagus nerve disconnected, a pathway that helps regulate digestion, among other things.
As a result, these rodents were unable to remember information related to their environment, as explained by the main author of the work, Andrea Suarez, a PhD candidate in biology at the University of Southern California:
We observed failures in hippocampal memory when we broke the communication between the gut and the brain. These memory deficits were coupled with harmful neurobiological consequences in the hippocampus.
In the event of a rupture of this nerve pathway, they were able to observe, among other things, significant damage to markers present in the brain, which are essential for the growth of new neuronal connections and new cells. These abnormalities, however, do not seem to have had any effect on the rodents' anxiety level or their weight, as the scientists point out.
New light shed on bariatric surgery?
However, the researchers alert to an issue that has been little considered until now, which has been brought to light by their discoveries: that of the potentially deleterious consequences of bariatric surgery on memory.
This set of techniques which aim to treat obesity by modifying the digestive system of patients could have unsuspected effects on some of their cognitive capacities, as the authors indicate in their publication:
Our findings could raise an important and timely medical question that deserves further research: could bariatric surgery and other therapies that block brain-intestinal signalling harm memory?
An invisible war could be playing out between patients' brains and the digestive systems, without anyone noticing it.
