Thermal taster status: Temperature modulation of cortical response to sweetness perception

Sally Eldeghaidy,Qian Yang,Turki Abualait,Ann-Marie Williamson,Joanne Hort,Susan T Francis

doi:10.1016/j.physbeh.2020.113266

Abstract

Temperature is known to impact taste perception, but its reported effect on sweet taste perception in humans is inconsistent. Here, we assess whether thermal taste phenotype alters the temperature modulation of the brains’ response to sweet samples and sweet taste perception. Participants (n = 24 balanced for thermal tasters (TT) and thermal non-tasters (TnT), 25 ± 7 years (mean ± SD), 10 males) underwent a thermal taste phenotyping session to study responses to cooling and warming of the tongue using a thermode. In a separate session, functional Magnetic Resonance Images (fMRI) were collected during sweet samples (87 mM sucrose) delivery at two temperatures (‘cold’ (5 ± 2 °C) and ‘ambient’ (20 ± 2 °C)) and the perceived sweetness intensity rated.In the phenotyping session, TTs had heightened perceptual temperature sensitivity to cooling and warming of the tongue using a thermode compared to TnTs. Although there was no significant effect during the fMRI session, the fMRI response to the ‘cold sweet’ sample across all participants was significantly increased in anterior insula/frontal operculum and mid-insula compared to the ‘ambient sweet’ sample, likely to reflect the perceptual difference to temperature rather than taste perception. TTs showed significantly increased fMRI activation patterns compared with TnTs and an interaction effect between thermal taster status and sample temperature, with TTs showing selectively greater cortical responses to ‘cold sweet’ samples compared to TnTs in somatosensory regions (SI and SII).The increase in cortical activation in somatosensory cortices to the ‘cold sweet’ stimulus correlated with perceptual ratings of temperature sensitivity to the thermode. The results highlight the importance of investigating the effects of thermal taster phenotype across a range of temperatures representing the reality of consumer consumption to beverages.

Highlights

Temperature is known to impact taste perception [1,2,3], level of acceptance [4] and emotional response [5, 6] to many foods and bev erages
Thermal tasters reported the intensity of thermally-induced tastes between weak and strong on the general Labelled Magnitude Scale (gLMS), with an average intensity rating across all tastes of just below moderate (Fig. 2A (i))
This four-point integer scale will have reduced sensitivity to detect the small differences in sweetness intensity perception, and the use of a continuous gLMS should be considered for future functional Magnetic Resonance Images (fMRI) studies

Summary

Introduction

Temperature is known to impact taste perception [1,2,3], level of acceptance [4] and emotional response [5, 6] to many foods and bev erages. Electrophysiology studies by Wilson and Lemon [11] showed that warming sucrose solutions to 30 ◦C increased gustatory neuron responses in the nucleus of the solitary tract (NTS) and the medulla, whilst cooling to 16 ◦C or 18 ◦C inhibited gustatory neuron responses. These studies provide evidence of temperature-taste interactions of sweet taste at the central level, but the impact of temperature on sweet taste perception in the human brain and how this varies with individual taster status has not been explored

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Discussion

Conclusion