PbN calcium imaging

This study explores how taste and food-related sensory information is processed in the parabrachial nucleus (PbN) of the pons in awake, unrestrained rats using one-photon calcium imaging. The PbN, long considered a critical taste relay in non-primate mammals, was examined for both its temporal stability in taste responsiveness and its responses to solid food and food odors.Findings revealed that individual PbN neurons are generally broadly tuned, responding to multiple basic taste qualities (sweet, salty, sour, bitter, umami), but their tuning profiles shifted significantly over days and weeks. Despite this variability, population-level patterns consistently differentiated taste qualities, supporting the across-unit pattern theory of taste coding over the labeled line theory.The study also uncovered robust PbN responses to solid foods (e.g., chocolate, peanuts) and their associated odors, although neural responses to odors were more similar to licking tastants than to consuming food. Notably, PbN responses to food involved sensorimotor integration, reflecting not only sensory properties but also motor-related feedback from appetitive and consummatory behavior. Network activity analyses distinguished licking and odor sampling from food approach, eating, and grooming, suggesting that the PbN encodes complex, multimodal behavioral functions.Collectively, these results challenge the traditional view of the PbN as a simple relay for taste and instead position it as an integrative hub involved in processing gustatory, olfactory, and somatosensory information. Moreover, the findings emphasize the importance of population coding in maintaining perceptual stability.