Tasty Read Free Page A

tracts of DNA. Having that blueprint would enable them to clone copies of the receptor so they could easily study its structure and workings.
    In a short span of time, science had become quite adept at slicing, dicing, and sorting these once-indistinguishable molecular strands. At NIH, scientists found a way to turn the scarcity of taste receptors to their advantage: They used a technique that plucked only the most unusual DNA snippetsfrom across the tongue, separating them from more generic strings. Some of these had to contain the material for taste. Next, they took each fragment and injected it into taste cells harvested from rodents. If it latched onto the DNA in the cell, it was a taste receptor gene. This was, roughly speaking, like putting a toddler in a room with a woman you think may be the mother: if they hug, then you know they’re related.
    It worked: the scientists found half of a rodent gene for a sweet receptor; the second half was found soon after, and then the analogous human gene for sweetness. Their double genes mean that sweet receptor molecules come in two parts that fit together like a train coupling. They are bizarre, Lovecraftian-­looking things, tangled skeins of seven coils stuck in the surface of a taste cell. One coil reaches out into the void to snag sugar molecules floating by. When it does, an electrochemical chain reaction begins that travels all the way to the brain, igniting a burst of pleasure.
    Elsewhere, scientists were starting to crack another once-intractable problem, the subjectivity of taste. A few years after the sweet receptor discovery, volunteers in an experiment at the University of Groningen in the Netherlands lay on a table with pacifiers connected to long straws in their mouths. They were then slid into a magnetic resonance imaging (MRI) scanner that recorded their brain activity as they sipped bitter tonic water through the straws. Later, they were scanned while looking at photos of people grimacing in response to a taste of a drink, and again as they read brief scripts intended to evoke distaste or disgust. The purpose of this experiment, run by neuroscientist Christian Keysers, was to explore the relationship between tastes and emotions. During the 1990s, the emergence of this type of scanner, called a functional MRI (fMRI), allowed scientiststo see which parts of the brain were active when a person ate or drank, smelled an aroma, or read—anything that could be done while one’s head was immobilized.
    There were limits to this approach. It showed associations between real-world actions and arcing networks of neurons in the brain, but not exactly what those associations meant. But it was a revealing waypoint between the chemical reaction of taste on the tongue and the mind itself.
    Their findings were strange. As volunteers imagined bitterness in a story, or saw photos of a wince of distaste, their brains experienced a “bitter” reaction. These patterns varied slightly in each part of the experiment, reaching out to encompass different parts of the brain. Taste seemed to be a cornerstone of higher functions such as imagination and emotion.
    The next twist in this story is still being written; it hinges on certain lingering mysteries. Flavor remains frustratingly paradoxical. Like other senses, it’s programmed by genes; unlike them, it is also protean, molded by experience and social cues, changing over the course of a lifetime. This plasticity is wild and unpredictable: people can learn to like or dislike almost anything, which is why the range of flavors in the world is seemingly infinite, and why the old tongue map was useless.
    Everyone lives in his or her own flavor world, which takes form during early childhood and evolves over the course of our lives. This world is created by the clash of ancient evolutionary imperatives meeting a lifetime’s worth of high-octane processed foods, cultural cues, and commercial messages.
    The flavor