Flavour perception is a complex sensory experience that arises from the intricate interplay between taste and smell. While we often regard taste as a distinct sensation originating from our taste buds, recent research from Karolinska Institutet in Sweden challenges this traditional view. Published in the esteemed journal Nature Communications, this groundbreaking study reveals that the brain’s taste cortex processes certain aromas as if they were genuine tastes, shedding light on why sugarless flavoured drinks can still be perceived as sweet.
The human experience of flavour is not a mere aggregation of taste and smell but rather a sophisticated integration of these sensory inputs. Central to this process is the phenomenon of retronasal olfaction, where aromas from food and drinks travel from the oral cavity to the nasal passages during consumption. This pathway enables the brain to marry the chemical signals of taste with those of smell, creating the unified perception we know as flavour. Until now, however, the precise neural underpinnings of this integration, particularly the temporal and spatial dynamics within the brain, remained elusive.
Researchers at Karolinska Institutet employed cutting-edge functional magnetic resonance imaging (fMRI) techniques to explore where and when this integration occurs. Their investigation centered on the insular cortex, often dubbed the taste cortex, which is traditionally associated with processing gustatory signals. Contrary to prior assumptions that flavour integration primarily occurs in higher cortical regions such as the frontal cortex, the study provides compelling evidence that integration begins much earlier and deeper within the insula. This early convergence of taste and smell signals suggests that the taste cortex encodes a shared neural representation of flavour.
The experimental design was meticulous. Twenty-five healthy adult participants were trained to associate specific taste qualities—namely sweet and savoury—with corresponding aromas. This conditioning allowed researchers to establish a robust baseline for how the brain discriminates these sensory inputs. During subsequent fMRI sessions, participants were exposed either to purely tasteless aromas or to tastes without accompanying smells. An advanced machine learning algorithm was then employed to decode the neuroimaging data, discerning patterns of brain activity characteristic of sweet and savoury stimuli.
Strikingly, the results demonstrated a significant overlap in the neural activation patterns elicited by actual tastes and their associated aromas within the taste cortex. When participants experienced sweet or savoury aromas without any gustatory input, their insular cortex responded in a manner indistinguishable from when they tasted corresponding flavours directly. This revelation elucidates why flavoured waters without sugar can nonetheless evoke a sensation of sweetness: the brain essentially interprets the aroma as a taste, blurring the sensory boundaries between smell and gustation.
Beyond its immediate implications for sensory neuroscience, this study holds profound consequences for understanding human eating behaviour. The joint neural coding of taste and aroma in the insula may underlie the powerful appeal of flavour combinations that stimulate both sensory channels synergistically. Such integrative processing could potentially drive cravings, influencing dietary choices and, by extension, contributing to overeating and obesity—an increasingly pressing public health concern.
Janina Seubert, senior researcher and co-author, emphasizes the transformative nature of these insights. By revealing that the brain does not treat taste and smell as isolated entities but creates a unified flavour code early in sensory processing, the study challenges longstanding paradigms in sensory biology. This integrated flavour representation might be pivotal in shaping individual taste preferences as well as broader food habits across populations, highlighting a complex sensory foundation for culinary culture and nutrition.
Future research trajectories emerging from this work are both fascinating and far-reaching. The team at Karolinska Institutet intends to probe whether similar neural mechanisms govern the perception of orthonasal odours—aromas detected through the external nostrils, such as those encountered while walking through a supermarket. If changing environmental smells can reconfigure taste cortex activation, this could explain why ambient food aromas instinctively guide consumer behaviour, subtly modulating cravings and food selection.
Such investigations may illuminate the neurobiological basis for shopping experiences where the smellscape of a grocery store shifts the perceived taste of food items in real time, potentially affecting purchasing decisions. This knowledge could inform the development of healthier food environments or marketing strategies that harness neural flavour coding to promote better nutrition without sacrificing sensory satisfaction.
The experimental findings also offer exciting possibilities for the food and beverage industries, especially in the burgeoning market for low-calorie and sugar-free products. By exploiting the brain’s tendency to integrate aroma and taste within the insular cortex, manufacturers can craft beverages and foods that deliver the sensory pleasure of sweetness without added sugars. This science-driven approach aligns with public health goals aimed at reducing sugar consumption while maintaining palatability.
Technically, the use of machine learning algorithms to decode brain imaging data underscores a significant advance in neuroimaging analytics. These computational models were capable of discerning subtle neural patterns that correlate specifically with flavour experiences, validating the concept of a shared neural code for taste and retronasal odours within the insula. This methodological innovation opens new avenues for precise mapping of sensory representations in the human brain.
The collaborative nature of the research further bolsters its credibility. Scientists from Karolinska Institutet partnered with international colleagues in Turkey, combining expertise in clinical neuroscience, neuroimaging, and sensory psychology. Funded by prestigious organizations including the European Research Council and the Swedish Research Council, the study reflects a commitment to advancing both fundamental understanding and practical applications in sensory science.
In summary, this seminal study redefines the neural landscape of flavour perception by demonstrating that the human insula integrates taste and retronasal odour signals into a unified, flavour-specific neural code. This discovery deepens our understanding of how aromas alone can simulate tastes, offering a neurobiological explanation for the sweetness perceived in flavoured waters without sugar. The findings hold far-reaching implications for public health, food technology, and the neuroscience of sensory perception, carving new paths for research and innovation in the realm of human flavour experience.
Subject of Research: People
Article Title: Tastes and retronasal odours evoke a shared flavour-specific neural code in the human insula
News Publication Date: 12-Sep-2025
Web References:
https://doi.org/10.1038/s41467-025-63803-6
References:
Khorisantono, P. A., Veldhuizen, M. G., & Seubert, J. (2025). Tastes and retronasal odours evoke a shared flavour-specific neural code in the human insula. Nature Communications. https://doi.org/10.1038/s41467-025-63803-6
Keywords: Sense organs, Olfactory perception, Sensory perception, Taste receptors, Neuroscience, Foods, Food science, Food chemistry, Health and medicine, Life sciences, Psychological science
