Eating appears to be organized at the cellular level similarly to a relay race: while we consume food, different groups of neurons take turns until we have ingested the right amount of energy. This insight comes from a recent study by scientists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU). Through this intricate process, the brain likely regulates our food intake to prevent overeating or under-eating. Disruptions in this mechanism may result in eating disorders, such as anorexia or binge eating. These findings have been published in the Journal of Neuroscience.
To maintain our health, it’s essential to consistently restore our energy levels through food intake. This regulation occurs in the hypothalamus, a key control center within the brain. The hypothalamus is constantly gathering critical information from our body and surroundings, including factors like the time of day or our blood sugar levels. Based on this information, it prompts certain instinctive behaviors, such as going to sleep when it gets dark or heading to the fridge when hunger strikes.
But how does the brain ensure that we continue eating even after our initial hunger fades and stretch receptors in our stomach signal that food is present? “When we consume food, we transition quickly from what’s known as ‘appetitive’ behavior to ‘consummatory’ behavior,” says Prof. Dr. Alexey Ponomarenko, who leads the Professorship of Systemic Neurophysiology at the Institute of Physiology and Pathophysiology at FAU. “There’s still much we don’t understand about how the brain regulates the length of this consummatory phase. It needs to be just right—not too long or too short—to provide us with the appropriate energy intake.”
Under Prof. Ponomarenko’s guidance, the FAU team, in collaboration with researchers from the University Hospital of Cologne, examined the brain’s activity during eating. They focused on the mouse hypothalamus, which exhibits structural similarities to that of humans. “We utilized an artificial intelligence approach to analyze the electrical activity in a specific part of the hypothalamus,” explains Mahsa Altafi, a mathematician and doctoral student at FAU, who co-authored the study. “This enabled us to identify which neurons become active—or generate electrical impulses—at particular moments while eating.”
Sequential activation of four distinct neuron groups
The researchers discovered four different groups of neurons that activate in a specific sequence during the eating process. These neuron groups collaborate much like relay runners, each playing a role in various phases of the process. “We believe these groups assess body signals like blood sugar levels, hunger hormones, and stomach fullness differently,” says Prof. Ponomarenko. For example, the fourth group may prioritize stretch sensor signals more than the first group. “This mechanism allows the hypothalamus to help regulate our food intake effectively.”
The scientists also explored how neurons within each group communicate with one another. It’s well-known that neurons have varying activity rhythms: there are moments when they are very excitable and others when their activity is minimal. These alternating phases often occur many times per second. For effective communication, neurons need to oscillate at the same rhythm. It’s akin to using walkie-talkies: if the devices are not tuned to the same frequency, all you will hear is static.
“We have demonstrated that the groups of neurons engaged in food intake communicate using the same frequencies,” says Prof. Ponomarenko. “In contrast, neuron groups involved in other activities—like exploring or social interactions—tend to communicate on different channels.” This likely facilitates easier information exchange among neurons involved in eating, allowing the process to conclude appropriately. This discovery could have clinical implications: advancements have already made it possible to influence neurons’ rhythms externally, for instance, using oscillating magnetic fields. Enhancing communication among these “feeding teams” could potentially be beneficial. If successful, it may help in treating eating disorders—a long-term aim.
“In mice, the oscillatory behavior of neurons can be directly influenced through optogenetic methods,” says FAU researcher Ponomarenko. “We are planning a follow-up study to examine how these influences affect their feeding habits.”
