Just by Looking at It, I Think It’s a Red

Everybody knows that one wine enthusiast that insists you must let the wine ‘breathe’ and exclaims “Ah, we have some truly wide legs on show here! What a treat!”, in response to the swirl of their glass.

Famous for being the city to where Popes fled following the corruption of Rome in the 14th century, Avignon should also be celebrated for its location in the South of France, a region famous for its wine. Though its sanctity should not be understated, its wine must not be either.

Figure 1. Me and two friends at the Carré du Palais wine tasting.

After walking into the refurbished bank vault at the Carré du Palais, the crisp, cool air hit my skin like the droplets of a bright Sauvignon Blanc with notes of Asian pear and celery. As we all took our places, there were 2 clear wine glasses and 1 small black wine glass that, in my blatant naïvety, I thought was for water. After integrating the sommelier for most of the wine tasting’s duration, he informed me that, in fact, the 1 small black wine glass was for white wine. He stated that our perceived taste of the wine can be influenced by the color because, as everyone knows, a deep yellow is probably an aged Riesling and a deep gold is probably a Chardonnay. This is referred to as ‘crossmodal bias’ (Verhagen and Engelen, 2006), a phenomenon in which one sensory modality (vision) can influence another (taste).

Figure 2. The two clear wine glasses and smaller black wine glass that caused confusion.

I thought this was a very fascinating precaution to take. To investigate the relationship between taste and vision, Rolls and Baylis (1994) recorded singular neurons from five macaques. Food related visual stimuli was presented to macaques and directly after, five different taste stimuli were delivered intraorally. It was found that 29.7% of neurons in the primary taste cortex were bimodal; they were found to have visual responses as well as olfactory responses (Rolls and Baylis, 1994). This discovery exhibits the ability of these sensory modalities to ‘communicate’ early on and can help us understand the phenomenon of crossmodal bias.

The sommelier also made a point to smell the wine deeply before taking his first sip. Following in his footsteps, I tried it. Though I didn’t pick up the hints of black current that he was noting, I did get a sense for the taste that was to come. In 1963, Thompson et al. suggested that sensory information entered its appropriate primary cortex brain region and then, through higher order processing, converged with other sensory modalities to create a more cohesive cognitive stimulus (Thompson et al., 1963). More recent discoveries suggest that the sensory modalities converge much sooner than this (Small et al., 2013). The piriform cortex, a structure within the primary olfactory cortex known to encode for odor memories (Meissner-Bernard et al., 2019), was found to contain neurons that selectively respond to taste (Small et al., 2013). Single neurons in the primary olfactory cortex of 19 rats were found to respond to taste solutions to the tongue (Small et al., 2013). This suggests that there is direct communication between sensory systems. That is, crossmodal bias occurs through exchanges of information between primary sensory systems.

Figure 3. Earlier models suggested a convergence pathway similar to (A) but findings from Small et al. (2013) suggest a schematic more like (B).

Immediately after telling my boyfriend about my cathartic wine tasting, he pronounced that sommeliers are simply full of it. In fact, in a study done by Castriota-Scanderbeg et al. (2005) investigating the differences between sommeliers and naïve research subjects, it was found that sommeliers actually have more refined olfactory and taste perception sensitivity (Castriota-Scanderbeg et al., 2005). 7 male sommeliers and 7 males with no wine tasting training were given either wine or glucose and a subsequent functional magnetic resonance imaging (fMRI) was performed. The left insula, orbit-frontal cortex, and bilateral dorsolateral prefrontal cortex were significantly more involved in wine tasting of sommeliers in comparison to naïve subjects (Castriota-Scanderbeg et al., 2005). Modulated by expertise, these regions represent areas where taste and olfactory stimuli converge and therefore give rise to the representation of flavor (Castriota-Scanderbeg et al., 2005). Moreover, in comparison to glucose, the wine elicited a neural response after the initial taste period which the researchers attribute to the presence of olfactory stimulus (Castriota-Scanderbeg et al., 2005) giving more evidence to the influence of smell on taste.

Over the past 50 years, the well-established organization of sensory systems has been dissolved through discoveries of sensory-sensory connectivity and the influences of one sensory modality on another. So, next time you uncork a nice bottle of wine, or dare I say, screw the top of your $3 bottle, recognize the convergence of your senses.

References

Baylis LL, Rolls ET (1994) Gustatory, olfactory, and visual convergence within the primate orbitofrontal cortex. Journal of Neuroscience 14(9):5437-5452. doi: 10.1523/JNEUROSCI.14-09-05437.1994

Castriota-Scanderbeg A, Hagberg GE, Cerasa A, Committeri G, Galati G, Patria F, Pitzalis S, Caltagirone C, Frackowiak R (2005) The appreciation of wine by sommeliers: a functional magnetic resonance study of sensory integration. NeuroImage 25(2):570-578. doi: 10.1016/j.neuroimage.2004.11.045

Rolls ET, Deco G (2002) Computational neuroscience of vision. Oxford University Press, Oxford (2002)

Small DM, Veldhuizen MG, Green B (2013) Sensory neuroscience: taste responses in primary olfactory cortex. Current Biology 23(4): R157-R159. doi: 10.1016/j.cub.2012.12.036

Thompson RF, Johnson RH, Hoopes JJ (1963) Organization of auditory, somatic sensory, and visual projection to association fields of cerebral cortex in the cat. Journal of Neurophysiology 26(3): 43-364. doi: 10.1152/jn.1963.26.3.343

Verhagen JV, Engelen L (2006) The neurocognitive bases of human multimodal food perception: sensory integration. Neuroscience and Biobehavioral Reviews 30(5):613-650. doi: 10.1016/j.neubiorev.2005.11.003

Photos

Figure 1 and 2 were taken by me

Figure 3: Small DM, Veldhuizen MG, Green B (2013) Sensory neuroscience: taste responses in primary olfactory cortex. Current Biology 23(4): R157-R159. doi: 10.1016/j.cub.2012.12.036