Cortical Coding of Gustatory and Thermal Signals in Active Licking Mice

Abstract

Eating behaviors are influenced by the integration of gustatory, olfactory, and somatosensory signals, which all contribute to the perception of flavor. Although extensive research has explored the neural correlates of taste in the gustatory cortex (GC), less is known about its role in encoding thermal information. This study investigates the encoding of oral thermal and chemosensory signals by GC neurons compared to the oral somatosensory cortex. In this study, we recorded the spiking activity of more than 900 GC neurons and 500 neurons from the oral somatosensory cortex in mice allowed to freely lick small drops of gustatory stimuli or deionized water at varying non-nociceptive temperatures. We then developed and used a Bayesian-based analysis technique to assess neural classification scores based on spike rate and phase timing within the lick cycle. Our results indicate that GC neurons rely predominantly on rate information, although phase information is needed to achieve maximum accuracy, to effectively encode both chemosensory and thermosensory signals. GC neurons can effectively differentiate between thermal stimuli, excelling in distinguishing both large contrasts (14{degrees}C vs. 36{degrees}C) and, although less effectively, more subtle temperature differences. Finally, a direct comparison of the decoding accuracy of thermosensory signals between the two cortices reveals that while the somatosensory cortex showed higher overall accuracy, the GC still encodes significant thermosensory information. These findings highlight the GCs dual role in processing taste and temperature, emphasizing the importance of considering temperature in future studies of taste processing. Key PointsO_LIFlavor perception relies on gustatory, olfactory, and somatosensory integration, with the gustatory cortex (GC) central to taste processing. C_LIO_LIGC neurons also respond to temperature, but the specifics of how the GC processes taste and oral thermal stimuli remain unclear. C_LIO_LIThe focus of this study is on the role of GC neurons in the encoding of oral thermal information, particularly compared to the coding functions of the oral somatosensory cortex. C_LIO_LIWe found that while the somatosensory cortex shows a higher classification accuracy for distinguishing water temperature, the GC still encodes a substantial amount of thermosensory information. C_LIO_LIThese results emphasize the importance of including temperature as a key factor in future studies of cortical taste coding. C_LI