New Publication in Neuron: "Feeding-induced olfactory cortex suppression reduces satiation"
Researchers from Charité – Universitätsmedizin Berlin and ECN members present novel insights into the role of olfaction in satiation and binge eating.
The research demonstrates in mice that the sense of smell plays a crucial role in determining when a meal ends. During rapid and highly rewarding eating, activity in the olfactory cortex is suppressed, which delays sensory satiation and extends food intake. This suppression effect is not observed in the gustatory (taste) cortex.
Key points include:
Mechanism: Olfactory signals in the piriform cortex are centrally inhibited during fast eating, weakening sensory satiation.
Causality: Inhibiting the olfactory cortex increases food intake, while activating it leads to earlier meal termination.
Reward pathway: Inhibitory neurons in the olfactory tubercle, part of the reward system, mediate this suppression.
Control: The gustatory cortex does not exhibit this suppression pattern.
Contextually, these findings offer a neurobiological explanation for how sensory satiation diminishes during overconsumption at high eating speeds. The results align with recent human studies (e.g., Wageningen’s RESTRUCTURE project) indicating that food texture and eating speed affect energy intake, emphasizing the importance of sensory signals in controlling portion size and feelings of fullness.
Schematic representation of activated neurons in the olfactory cortex during a live experiment using a miniature microscope, when mice eat slowly. The mice were offered nutritionally identical food with different flavors (strawberry and chocolate) as well as a sugar solution. We observed a clearly separated representation of neurons responding to strawberry flavor (blue), chocolate flavor (orange), and the sugar solution (green). During fast eating (“binge feeding”), these neurons are suppressed. © Neuron | Johenning
In this section, study lead PD Dr. Friedrich Johenning answers questions about the research findings.
What was the research question or scientific inquiry behind your study?
We wanted to understand how the sense of smell influences feeding behavior—especially why mammals tend to consume more during fast or binge-like meals, even beyond homeostatic need. We hypothesized that the olfactory cortex, the brain region responsible for processing smells, plays an active role in this process. The underlying concept is sensory-specific satiation: conscious sensory experience of flavor can enhance and prolong the feeling of fullness.
How did you approach the topic?
We equipped mice with miniaturized microscopes that allowed us to observe brain activity in real time as the animals moved freely and ate. This enabled us to track how olfactory sensory representations in the brain changed depending on feeding speed. In addition, we used optogenetics to selectively switch the olfactory cortex on or off with light to test its causal role in feeding.
What did you discover?
During slow feeding, the olfactory cortex responds distinctly to different flavors with the activation of flavor-specific neuronal ensembles. In contrast, during binge feeding, activity in this region is broadly suppressed, a phenomenon we did not observe in the taste-sensing gustatory cortex. This suppression delays the onset of satiation—mice eat longer. When we optogenetically silenced the olfactory cortex during feeding, mice ate significantly more; when we activated it, they stopped eating sooner. This demonstrates that the olfactory cortex acts as a regulatory switch for sensory-driven satiation.
Was there anything that surprised you?
We were especially surprised to discover that this suppression is not inherited from the olfactory sensory neurons, but is instead driven by an internal value system—specifically, inhibitory neurons in the olfactory tubercle, a reward-related brain region. This means that the more valuable the food, the more the olfactory cortex is “turned down” during fast feeding, thereby reducing sensory satiation.
What’s your takeaway?
Our results show that smell is not just passively involved in eating—it is actively regulated depending on how much we like the food and how quickly we eat. This may help explain why certain eating patterns and food types lead to overconsumption. In the long term, this insight could inform new strategies for treating eating disorders and obesity.
Reference: Lo, H., Cañedo Riedel, W., Tantirigama, M.L.S., Kelsch, W., Schmitz, D., Johenning, F.W., et al. (2025). Feeding-induced olfactory cortex suppression reduces satiation. Neuron.
https://doi.org/10.1016/j.neuron.2025.07.020
Contact:
PD Dr. Friedrich Johenning
Institute for Cell Biology and Neurobiology
Neuroscience Research Center
Charité – University Medicine Berlin
Links
Link to the original article on the Cell Press website
Link to the Charité website of the Johenning Lab (Sensory biology of feeding