Neurons that protect us from dying from poisoning
From a young age, with a single intake, our body is enough to associate toxicity with a product or food, which reveals the connection of the neural networks between the brain and the intestine.
Omnivorous mammals feed us a wide variety of foods. Driven by curiosity, primates, rodents, and canids try new foods and, at the same time, we have learned to avoid them if eating them has made us dizzy or sick before; this is true even after a single bad experience. It's crucial to learn which foods are toxic to us because survival is key. But how can we learn this from a single exposure?
Toxicity reactions usually manifest first in the gut, because the toxin usually causes nausea and vomiting to expel what the body rejects. Conditional aversion to certain tastes and smells is not inherent but learned., and we express our displeasure in different ways. Humans feel dizzy, make explicit faces, and communicate this to others.
In experiments with rats and mice, rodents throw food out of the feeder or bury it so that no one else can eat it. In observations in nature, coyotes roll on the ground and urinate on food they consider toxic to also provoke rejection by their peers. All of these reactions demonstrate that learning occurs and that our brains are capable of relating physical discomfort with poisoning due to the ingestion of a specific product.
Besides, This aversion to certain tastes usually persists throughout life and is very difficult to reverse.The gut-brain connection is bidirectional. The nervous system regulates digestion and controls peristaltic movements, but at the same time, our gut generates signals that impact our emotions, cognition, and behavior.
Gut-Brain Connection
In the learning of conditioned aversion to certain foods, different neural networks intervene. The first is the one that begins in the mouth with the sense of taste when we ingest a new product, which connects to the neurons of the gustatory cortex and then to an area of the brain called the amygdala, which allows us to "record" this new taste for the specific food we ingest.
Another neural network is the one that links intestinal discomfort with a region of the hindbrain, whose neurons produce a specific neurotransmitter related to the sensation of pain, which also connects to the amygdala. Recent research in mice demonstrates how the interaction between these neural connections and the subsequent learning occurs such that, if we survive the experience, Just the smell or taste brings back all the discomfort and we avoid eating it..
In these experiments, researchers give mice a fruit-flavored drink. One group of animals has been given the liquid for days without any harm, while another group is given it for the first time. After half an hour of drinking, both groups are induced to feel nauseous by administering lithium chloride intraperitoneally, and they observe which brain regions are activated.
After a two-day interval of giving them only water, they observe that if they now give them a choice between water and a fruit-flavored drink, the mice that had previously become accustomed to drinking the fruit-flavored drink without any effect indiscriminately drink both water and the flavored drink, while those that later significantly prefer the flavored drink. How is this?
Neurons that protect us from toxins
Researchers determine that there are neurons in the amygdala involved in the control of emotions that They are activated when a food is first tasted, also when nausea occurs, and again when they are presented with a drink they associate with a negative experience.. Thus, both the neurons that have identified and processed taste, appearance, and smell, as well as the group of neurons in the hindbrain that control the sense of discomfort and pain, project to the same area of the amygdala. When a taste is new, these activated neurons in the amygdala remain on alert for a certain period. If no signal of discomfort arrives from the gut, the food is not classified as toxic. If, on the other hand, during this alert period the neurons in the hindbrain signal that the body is not well, the amygdala will characterize this delicacy as probably toxic and generate the uncontrolled reaction of aversion and rejection, even reliving the nausea.
The researchers They have genetically engineered these neurons that come from the back of the brain and indicate intestinal discomfort.. If they are genetically activated, regardless of the food, the mice feel nauseous and will reject the food. On the contrary, if the function of these neurons is also genetically annulled, the animals are unable to associate a specific food with nausea and will not present conditioned aversion.
Therefore, natural selection has favored the creation of neural networks that protect the body from the ingestion of potential toxins, which can be somewhat staggered in time to allow the association of taste with the discomfort generated. The next time you say you don't like seafood at all or that you can't drink milk because it makes you vomit, you will already know why and how your body's physical reaction of conditioned aversion was generated.
