A brainstem signal reorganizes the neural code for taste
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.
A recent study from the University of Connecticut has revealed how the brainstem's locus coeruleus (LC) region can reorganize the neural code for taste in mice. The LC is a major source of norepinephrine, a chemical messenger that regulates arousal, attention, and stress responses. Researchers in the lab of Natale Sciolino, an assistant professor in physiology and neurobiology, found that activating the LC using light (optogenetics) influenced how taste-related neurons in the mouse gustatory cortex represented various taste stimuli.
Brief, or phasic, activation of the LC strengthened the relationship between neuronal activity and palatability, reorganizing the neural representation of taste to emphasize sucrose while shifting other tastes toward less palatable representations. In contrast, sustained, or tonic, activation of the LC did not produce the same effect, instead having fewer effects on taste representation.
The researchers caution that their findings do not establish that the neural changes altered the mice's subjective experiences or food preferences. Nonetheless, the stability of the sucrose representation suggests that the brain may prioritize the appeal of especially palatable foods when an animal must remain vigilant. Future research will explore whether these neural coding changes influence the animals' emotional and behavioral responses to taste, as well as their taste-evoked facial expressions, which serve as an observable readout of a taste's hedonic value.
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