David Hill, a neuroscientist and professor in UVA’s department of psychology, studies the development of taste. Hill’s course on the chemical senses—an undergraduate and graduate seminar—explores the biology of taste and smell, often considered the minor sensory systems. While hundreds of scientists study the development of vision and audition, only a handful of labs in the world study the neurobiology of taste development, and two of those labs are at UVA.

David Hill is not a supertaster—but he wouldn’t mind being one. Nearly 25 percent of us are supertasters—people with many more taste buds than average, which allows for more intense experiences of taste. “It’s a relatively easy diagnosis for a clinician to make,” says Hill. “I wouldn’t call it a disorder. If anything, it’s an enhancer.” “What we often think of as taste is really more smell than anything. You experience that if you have a cold,” Hill explains. “There’s nothing wrong with your taste system, but you’re not getting the airborne input. Really, we’re talking about flavor, the combination of smell, taste and touch.” We receive taste through taste bud receptors that send signals to peripheral nerves. The signals pass through the brainstem and on to the orbital frontal cortex in the brain. While taste and smell affect the same neurons in the same area of the brain, they take different pathways to get there.

Hill discounts the tongue map, which divides the tongue into sections according to specific taste receptors. “In one taste bud you’ll have as many as 50 cells, and each one of those can respond to multiple solutions,” says Hill. So where did the map come from? “In the early 1960s,” says Hill, “there was a famous investigator, Georg von Békésy, who had made major progress in understanding the auditory system. For whatever reason, he decided to study the taste system. He’s really the one who popularized the functional map of the tongue, and because he was so famous, people didn’t question it thoroughly.”

While there is significant data to contradict such an organization of tastes in the mouth, Hill says that the back of the mouth does tend to be sensitive to bitter tastes, perhaps as a protective mechanism; it’s the mouth’s last chance to expel toxic substances.

The division of taste into four or five discrete categories is also misleading. “It almost gets to be a philosophical debate,” says Hill. Other sensory experiences can be plotted along spectrums—the color spectrum or audio frequencies—but no chemical dimension provides a continuum for taste, so it appears to be organized into discreet groups: sweet, salty, sour, bitter and umami (the savory protein or amino acid taste). “But what happens when tastes are mixed?” asks Hill. “If you mix a salt and a sugar, do you have a salty-sugary taste, or do you create something unique?”

We may think of taste as changing with age, but Hill says that, biologically, taste buds remain the same. We don’t suddenly develop new receptors to help us appreciate blue cheese or red wine. Acquiring taste is learned behavior; therefore, changes in cortical processing may account for changes in taste preferences.

Aguesia, or loss of taste, can result from damage to the chorda tympani nerve. When the nerve is damaged, taste can be altered for weeks or months. While taste may not return to its original form, the system is remarkably regenerative. “You can think of it like skin,” Hill explains. “We’re sloughing off skin cells on about a 10-day program. We get new taste buds all the time, even in adulthood.”

For many, the loss of taste has a profound effect on quality of life, and Hill suspects future work may show aguesia has significant effects on digestion. “More and more it looks like taste has an important role in getting the gut ready for a meal,” he says. “You’ll have hormones released by way of neural control before the food gets to where it is going to be digested.” So while it may seem as though our sense of taste simply makes eating pleasurable, it actually provides practical help to our digestive system.

Cat Got Your Tongue?

Other animals experience taste differently than humans do. Cats, for example, can’t tell if food is sweet.

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The experience of spiciness isn’t transmitted through taste buds, instead pain receptors in the mouth react to capsaicin, a compound common in chili peppers.