Investigating the role of thermosensation in multimodal olfactory perception

Abstract

Every organism in their environment is exposed to a variety of sensory stimuli. The ability of living things to identify, categorise, and respond towards these external stimuli is most crucial for their survival. These sensory cues include visual, auditory, smell, taste, somatosensory, and temperature. Animals perceive these cues and integrate congruent and eliminate incongruent information from several sensory systems to make appropriate decisions. The mouse olfactory system is unique in a way that it has different subsystems that can detect a variety of stimuli with varying physico-chemical characteristics. The subsystems comprise of the Main olfactory epithelium (MOE), Septal organ (SO), Vomeronasal organ (VNO), and Grueneberg ganglion (GG) which enables the animals to detect and discriminate olfactory cues, mechanical pressure, pheromones like non-volatile cues and temperature cues. Thus far, these subsystems have been studied independently and the interactions among them are not well understood. Additionally, the role of the olfactory system in sensing the temperature also remains elusive. Hence, in this study, we focus on examining the effect of temperature on olfactory perception. We first investigated whether animals could discriminate different temperatures that they experience in their natural environment and the role of GG in sensing these temperatures. To accomplish it, we custom-built a thermo-olfactometer capable of delivering the odorized/non-odorized air of desired temperatures and standardized the critical parameters. When animals were trained to detect and discriminate different temperatures, we observed that the performance of animals reached the asymptotic phase in 1200-1500 trials, which showed a deficit after the GG of the animals underwent axotomy. We showed that animals could successfully discriminate temperatures. In contrast, animals that had sham surgeries showed no decrease in accuracy, thereby indicating the role of GG in temperature discrimination. Moreover, to understand how temperature affects olfactory perception, we trained the animals on a multimodal discrimination task i.e. animals were trained to discriminate different odours coupled to different temperatures. Our results showed faster learning in the multimodal task compared with the temperature discrimination. Taken together, our results reveal that animals can detect and discriminate temperature using their GG and it can modulate the olfactory perception.