Sniffing out meaning: Chemosensory and semantic neural network changes in sommeliers

Abstract

Wine tasting is a very complex process that integrates a combination of sensation, language, and memory. Taste and smell provide perceptual information that, together with the semantic narrative that converts flavor into words, seem to be processed differently between sommeliers and naïve wine consumers. We investigate whether sommeliers' wine experience shapes only chemosensory processing, as has been previously demonstrated, or if it also modulates the way in which the taste and olfactory circuits interact with the semantic network. Combining diffusion-weighted images and fMRI (activation and connectivity) we investigated whether brain response to tasting wine differs between sommeliers and nonexperts (1) in the sensory neural circuits representing flavor and/or (2) in the neural circuits for language and memory. We demonstrate that training in wine tasting shapes the microstructure of the left and right superior longitudinal fasciculus. Using mediation analysis, we showed that the experience modulates the relationship between fractional anisotropy and behavior: the higher the fractional anisotropy the higher the capacity to recognize wine complexity. In addition, we found functional differences between sommeliers and naïve consumers affecting the flavor sensory circuit, but also regions involved in semantic operations. The former reflects a capacity for differential sensory processing, while the latter reflects sommeliers' ability to attend to relevant sensory inputs and translate them into complex verbal descriptions. The enhanced synchronization between these apparently independent circuits suggests that sommeliers integrated these descriptions with previous semantic knowledge to optimize their capacity to distinguish between subtle differences in the qualitative character of the wine.

Keywords: connectivity; fMRI; flavor; language network; sommelier; taste; wine.

FIGURE 1

Each scan consists of a serial delivery of one of three different types of taste stimuli (a block). A block consists of a series of three, six, or nine presentations. An auditory cue was presented before each block to alert participants which type of stimuli (wine or solution) will be delivered. Each presentation starts with a 0.75 ml delivery of liquid over 3.00 s followed by a 7.00 s window to swallow. Each wine block was followed by a rinse (0.75 ml distilled water). Before the start of a new block, there was a rest period of 10 s. Blocks varied in length between 30 and 90 s, and the order of blocks was counterbalanced across subjects. The hemodynamic response function predicted for each block was schematically represented with the gray dotted line.

FIGURE 2

(a) Increase of fractional anisotropy (FA) in sommeliers as compared to naïve consumers in the superior longitudinal fasciculus (I, II, and III). (b) Macrostructural white matter (WM) connectivity in the atlas for SLF I, II, and III. (c) Violin plots for the four WM regions showing differences between sommeliers and controls. (d) Mediation analyses showing the effect of years of experience in the relationship between FA and the ability to discriminate wine complexity. The four clusters exhibiting significant differences between sommeliers and naïve consumers were used: three clusters within the right superior longitudinal fasciculus (I, II, and III) and one cluster within the left superior longitudinal fasciculus I. To assist us in interpreting the mediation result, we have represented the relationship between years of experience and performance in the discrimination task, and the differences in FA between the groups.

FIGURE 3

Brain activation for wine versus tasteless for naïve consumers (in green), sommeliers (in red), and the overlap between the two groups.

FIGURE 4

Main effect of group. Controls > sommeliers in yellow. Sommeliers > controls in blue.

FIGURE 5

Upper: brain activation for the interaction between group and type of wine. Lower: Brain activity in the right middle temporal gyrus and the right middle frontal gyrus is related to wine complexity in sommeliers (blue bars) but not in naïve consumers (gray bars).

FIGURE 6

Changes in brain network configuration between sommeliers and controls using as seeds 30 ROIs resulting from the group‐level F‐test contrast wines versus tasteless. In the upper part, all the significant interactions are superimposed in a 3D reconstruction of a brain surface template (Xia et al., 2013). The matrix of functional interactions between the 30 regions of interest is represented in the lower part. The color change from dark red to yellow indicates an increase in the t value of the significant connections. Blue cells represent no connection.

FIGURE 7

Changes in brain network configuration between sommeliers and controls using as seeds the middle temporal cluster resulting from the interaction between group and type of wine.