Sensory perception and the trigeminal nerve

I recently made black beans and rice for a sunny deck party in Alaska at the cabin. The remainder from the deck party went to another party that included many SE Asians. I made it mild (5 jalapenos and chili powder), or so I thought, but both parties reported back that it was too spicy to eat more than a small portion. This led me to ponder the what leads to variation in sensory perception of data generated by the trigeminal nerve.

The trigeminal nerve (with regards to eating) is responsible for heat and cold detection (e.g., mint feels cool, chili feels hot) as well as other components of texture (e.g., crunchiness, density, sponginess) and is a perfect partner for chemosensing (taste and smell, collectively known as flavour). Between these cranial nerves (I-olfaction; V-trigeminal; VII and IX-taste), we get a full rich experience in the mouth.

Is there variation in how the nerve operates or something at the level of perception? With the chemosenses, we can look at the receptors and other accessory agents in the sensing process but not as much with the trigeminal nerve. So, is it learned–eat hotter foods to tolerate more heat? If the latter, we loop back to the notion of preference and how it is shaped. My mother is Irish so I grew up with well prepared but not spicy food. Two weeks most summers though, she would go home to Carrandine and my father would take over the kitchen and bring the heat to burritos and chili. Despite so little hot food influence in my formative years, I prefer hot foods and carry chili peppers in my bag. Only 3 times in my life have I had food that was at my tolerance limit and this includes many authentically prepared dishes in personal homes in Asia, Europe, and the US. I also love anything minty–the stronger the better. My aggressive palate is also very sensitive to textures–I have no objection to mushroom flavour (broth/sauce) but cannot eat a mushroom. If I were a neuroscientist, I would probably make this my field of inquiry–uncover what drives this preference impulse and how such variation within and among cultures.

A not-so-great movie  (Perfect Sense, 2011) explored a global phenomenon in which humans gradually lost of each of the five traditional senses. When the sense of smell was lost, chefs focused on contrasting the basic tastes. When taste was lost, they concentrated on novel textures and colors to try to engage the palate (and keep their kitchens open). This engagement with multiple senses is the focus on cross-modal sensory science which has a core idea derived from common sense: all the senses contribute to the experience of eating and drinking. Afterall, anyone can identify the value of a carefully presented plate compared to cafeteria ‘slop’ on a plate. But, these sensory scientists want to uncover what the various roles of non-chemosensing components have in overall food/drink perception and hedonic value (positive-pleasure; negative-displeasure). For example, does color have a great impact than shape or is it texture or the room ambiance or the plate itself (shape and color)? There is still so much to explore within the chemosenses, let alone how the senses integrate in the experience of food and drink. At the very least, we know what we like and some of us can carry chili peppers around to feed the heat!

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