The decision-making process in our brain has long been a mystery to science. However, researchers at ETH Zurich have decoded the specific brain chemical and nerve cells responsible for such decisions: orexin as the messenger substance and the neurons that produce it.
The neuroscientific principles mentioned are important because a large number of individuals do not engage in sufficient physical activity. Many of us have likely chosen to forgo exercise in favor of other daily temptations at least once or multiple times. According to the World Health Organization, 80 percent of adolescents and 27 percent of adults do not get enough exercise. Additionally, obesity is rapidly rising, affecting not only adults but also children and adolescents.
Focus on orexin
“Despite these statistics, many people are able to resist the constantly present temptations and get enough exercise,” says Denis Burdakov, Professor of Neuroscience at ETH Zurich. “We wanted to understand what it is in our brain that assists us in making these decisions.”
Sure, here is the revised text:In their experiments with mice, the researchers demonstrated that orexin plays a crucial role in this process. It is one of over a hundred messenger substances active in the brain. While chemical messengers like serotonin and dopamine have been known for a long time and their functions largely decoded, orexin was discovered relatively recently, around 25 years ago. Scientists are now gradually uncovering its functions, and Burdakov is one of the researchers dedicated to studying orexin.
Existing knowledge can’t explain the choice
“In neuroscience, dopamine is often cited as the reason for our choices in various activities,” explains Burdakov. This neurotransmitter plays a crucial role in our overall motivation. “However, our current understanding of dopamine does not provide a simple explanation for why we might choose to exercise over eating,” the scientist elaborates. “Dopamine is released in the brain both when we eat and when we exercise, which doesn’t clarify why we make one choice over the other.”
In order to determine what drives certain behavior, the researchers set up a complex experiment for mice. In this experiment, the mice were given the freedom to choose from eight different options during ten-minute trials. The options included a running wheel and a “milkshake bar” where they could enjoy a standard strawberry-flavored milkshake. According to Burdakov, mice enjoy milkshakes for the same reasons people do: they contain high levels of sugar and fat and taste good.
Less time at the milkshake bar
In their experiment, the scientists compared different groups of mice: one group consisted of normal mice, and the other group had their orexin systems blocked, either with a drug or through genetic modification of their cells.
The mice with an intact orexin system spent twice as much time on the running wheel and half as much time at the milkshake bar as the mice whose orexin system had been blocked. Interestingly, however, the behavior of the two groups didn’t differ in experiments in which the scientists only offered the mice either the running wheel or the milkshake. This means that the primary role of the orexin system is not to control how much the mice move or how much they eat. Rather, it seems central to making the decision between one and the other when both options are available. Without orexin, the decision was strongly in favor of the milkshake, and the mice gave up exercising in favor of eating.
Helping people who do little exercise
The researchers at ETH Zurich believe that orexin may be responsible for decision-making in humans, as the brain functions involved are practically the same in both species. Daria Peleg-Raibstein, a group leader at ETH Zurich, who conducted the study with Denis Burdakov, stated that further verification in humans is needed. This could involve studying patients with restricted orexin systems due to genetic reasons, which affects about one in two thousand people who suffer from narcolepsy. Another approach would be to observe individuals receiving a drug that blocks orexin, as such drugs are authorized for patients with insomnia.
“If we understand how the brain arbitrates between food consumption and physical activity, we can develop more effective strategies for addressing the global obesity epidemic and related metabolic disorders,” says Peleg-Raibstein. In particular, interventions could be developed to help overcome exercise barriers in healthy individuals and those whose physical activity is limited. However, Burdakov points out that these would be important questions for scientists involved in clinical research in humans. He and his group have dedicated themselves to basic neuroscientific research. Next, he wants to find out how the orexin neurons interact with the rest of the brain when making decisions like the one between exercise and snacking.””