UConn researchers found that brief and sustained activation of an arousal-related brain region had markedly different effects on how the mouse brain encoded taste
Qichen (Will) Fan, a Ph.D. student in physiology and neurobiology lab, works with assistant professor Natale Sciolino in her lab at the Torrey Life Sciences Building on July 13, 2026. (Bri Diaz/UConn Photo)
Why might food seem appealing in one state of mind and less enticing in another? New UConn research offers insight into how the brain systems that regulate alertness and stress may reshape how taste is represented in the brain.
In a study published in Cell Reports, researchers in the lab of Natale Sciolino, an assistant professor in the department of physiology and neurobiology, found that activating a small brainstem region called the locus coeruleus changed how groups of neurons in the mouse gustatory cortex represented taste.
The locus coeruleus, or LC, is a major source of norepinephrine in the brain. Also called noradrenaline, this chemical messenger helps regulate arousal, attention, and responses to stress. The gustatory insular cortex processes information about taste, including its identity, intensity, and palatability - how appealing or aversive it is.
Scientists have long known that internal states such as illness and arousal can influence sensory processing. Until now, however, researchers had not directly tested how LC activity affects taste coding across populations of neurons in the gustatory cortex.
To investigate that connection, the team used optogenetics, a technique that allowed them to activate norepinephrine-producing LC neurons using light. Miniature microscopes recorded activity in the gustatory cortex of awake mice as taste stimuli were delivered through intraoral cannulas. The researchers then used computational analyses to identify patterns in the resulting neural activity.
They tested two patterns of activity: brief, or "phasic," LC stimulation and sustained, or "tonic," stimulation. Phasic LC activity is associated with momentary vigilance and shifts in attention, while elevated tonic activity is associated with heightened arousal and stress.
The effects on taste coding depended strongly on the pattern of LC activation. Brief stimulation strengthened the relationship between neuronal activity and palatability. At the population level, it reorganized the geometry of taste-related activity, increasing the neural separation between sucrose and the other basic tastes. Representations of salt, citric acid, and quinine shifted in a less palatable direction, while sucrose - the most palatable stimulus tested - remained comparatively stable.
The researchers also observed changes in the neural representation of taste mixtures and different sucrose concentrations. Together, the findings suggest that a brief burst of LC activity can rapidly reorganize how the gustatory cortex emphasizes behaviorally relevant information.
Sustained LC activation produced a different result. Although it triggered robust norepinephrine release, it affected fewer neurons in the gustatory cortex and did not expand neural representations along the palatability, mixture, or concentration dimensions. This contrast suggests that the LC does not act as a simple on-off switch: its influence on taste coding depends on its pattern of activity.
The researchers caution that the study measured neural activity, not the animals' subjective experiences, food preferences, or feeding decisions. It therefore does not establish that the neural changes altered how pleasant or unpleasant the mice found the tastes.
The stability of the sucrose representation nevertheless raises an intriguing possibility. The researchers hypothesize that when an animal must remain vigilant, the brain may preserve the appeal of especially palatable foods while shifting other tastes in a less palatable direction.
The next step is to determine whether these changes in neural coding alter the animals' emotional and behavioral responses to taste. Towards this goal, the lab is examining how LC activity influences what and how much mice consume, as well as their taste-evoked facial expressions. These characteristic orofacial reactions serve as an observable readout of a taste's hedonic, or emotional, value - revealing whether an animal responds to it as pleasurable or aversive. By connecting these reactions with neural activity, this work will test whether the neural patterns identified in this study translate into meaningful changes in how tastes are valued.
Fan, To, and Sciolino are the authors of "Locus coeruleus activation transforms cortical taste representations." The study is part of a broader research program in Sciolino's laboratory examining the neuroscience of taste. The lab received a National Institutes of Health R01 award in June to support related work.
Research reported in this story was supported by the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health (NIH) under Award Number R01DC023564 and by a Brain Research Foundation (BRF) Seed Grant under Award Number BRFSG2023-09. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH or the BRF.
