Intraoral thermal processing in the gustatory cortex of awake mice.

Oral temperature is a sensory cue relevant to food preference and nutrition. However, the cortical computation involved in processing thermosensory information in behaving animals remains largely elusive. In this study, we investigate how orally-sourced thermal inputs are processed in the gustatory cortex (GC), a cortical region typically studied for its role in processing another intraoral sensory cue - taste. Therefore, we used fiber photometry and electrophysiology to record neural responses from the GC of male and female mice presented with different innocuous temperatures (14 °, 25 ° and 36 °C) of deionized water. Our results demonstrate that GC neurons encode orally-sourced thermal information in the absence of taste, at both the single neuron and population level. Analysis of thermal-evoked responses showed broadly tuned neurons that responded to temperature in a mostly monotonic manner. Furthermore, spatial location plays a minor role with regard to thermosensory activity; with the exception of the most ventral GC, neurons reliably respond to and encode thermal information across the dorso-ventral and anterior-posterior cortical axes. Finally, decoding analysis revealed a small ensemble of GC neurons rapidly and accurately discriminate thermal information after the fluid is in contact with the mouth, providing additional evidence of the GC's involvement in processing thermosensory information important for ingestive behaviors. Altogether, our data reveal details of the cortical code for the mammalian intraoral thermosensory system in behaving mice and pave the way for future investigations on the GC functions and its operational principles with respect to thermogustation.