Columbia University Medical Center reveals that scientists have found that taste ultimately comes from the brain, not the tongue and they have manipulated mice brain cells to change the way something tastes to a mouse. (Columbia University Medical Center) 
 
 You probably know that we perceive five basic tastes, and that taste has something to do with the tongue and the brain. But a new study shows just how weird our perception of reality truly is: Scientists showed that all it takes to convince a mouse that their mouth is full of sweet nectar or bitter poison is the manipulation of a few brain cells. 
 
 [The chemistry that makes your wine taste good (or bad)] 
 
 Learning more about this mechanism could unlock secrets of the human brain, perhaps even paving the way for new treatments for eating disorders, the researchers say. 
 
 "This study really serves to reemphasize the concept that in essence our reality is nothing but electrical signals in our brain," said Charles Zuker of Columbia University’s Mortimer B. Zuckerman Mind Brain Behavior Institute. Zuker is the lead author of the new research, published in Nature on Wednesday. The results show that taste is hardwired in the brain, and can be triggered as easily by electrical signals as it can be by actual flavor chemicals. 
 
 The study built on Zuker's previous work, which showed that specialized cells in the tongue — designed to detect either sweet, sour, bitter, salty or umami tastes — corresponded to specialized cells in the brain. 
 
 [No, MSG isn't bad for you] 
 
 "Imagine these cells as being the keys of a piano," Zuker said. "You press the key and activate a wire that produces a specific sound. But it doesn't matter how you press the key. You could use finger, an elbow, a nose. It doesn’t matter how we tweak the cells; if you tweak the right cells you get the right signal." 
 
 Zuker hypothesized that he could activate or silence the brain cells being tweaked by the tongue cells, creating false perceptions of taste — and he was right. 
 
 By taking mice and training them to report what they were tasting ("It's not so easy for a mice to tell me this," Zuker quipped — but they were trained to move in particular directions when tasting bitter or sweet chemicals) Zuker and his postdoctoral co-author Yueqing Peng demonstrated that signals in the brain could create the experience of taste without any real stimuli. 
 
 They used optogenetics (explained in the video above) to selectively activate and deactivate the neurons associated with sweetness and bitterness. 
 
 "The biggest surprise was that they didn't just report sweet or bitter as they'd been trained to do, but much to our surprised they developed the full behavioral response," Zuker said. "We saw a mouse trying to clean its mouth of a bitter taste. This is extraordinary. There's nothing in there but water and the mouse is gagging, trying to get rid of a nonexistent chemical." 
 
 [These friendly food scientists want to make you feel good about eating chemicals] 
 
 There are more than 100 million neurons in a mouse's brain, but triggering just a few thousand of them was enough to create an experience that's supposed to be triggered by something material. Taste is important: It helps animals seek out the nutrients they need and avoid foods that could hurt them. But just like everything that goes on in the brain, it comes down to electrical signals — and those can always be hacked. 
 
 If you're willing to put a wire into your skull, anyway. 
 
 Zuker is hoping that further study will produce something useful for humans — no wires required. 
 
 "We're trying to figure out how all this is choreographed," he said, "how the brain uses this information to guide actions and behaviors." 
 
 If we can better understand the logic behind these circuits, he said, we might be able to find less invasive ways of tweaking them when they go wrong, as could be the case with certain eating disorders. 
 
 There are "bigger, sexier" ways to project the findings into the future, too, according to Zucker. 
 
 "Here we have a chunk of tissue that uses nearly a third of all of your energy and oxygen, yet it only weighs a small fraction of your total body weight, and it completely transforms the human condition," Zuker said. "It’s able to change fear into courage, sadness into happiness. How does it do it? Even though these are more abstract concepts than taste, I know they have to be encoded in circuits. If we could define the circuits involving courage, we could theoretically activate courage in the brain. But first we need to get the basics of how these processes work." 
 
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 Eating carbs may have given human ancestors a big brain boost ||||| Researchers in the US have turned taste on and off in mice simply by activating and silencing certain brain cells. This demonstrates for the first time that taste is hardwired in the brain, and not dictated by our tastebuds, flipping our previous understanding of how taste works on its head. 
 
 It was previously thought that the taste receptors on our tongue perceived the five basic tastes – sweet, salty, sour, bitter, and umami – and then passed these messages onto our brain, where it registered what we'd just tasted. But the new study shows that although our tongues do detect the presence of certain chemicals, it's our brains that perceive flavour. 
 
 “Taste, the way you and I think of it, is ultimately in the brain,” said lead researcher Charles S. Zuker from Columbia University Medical Centre. “Dedicated taste receptors in the tongue detect sweet or bitter and so on, but it’s the brain that affords meaning to these chemicals.” 
 
 Previous work by Zuker's lab discovered that our tongue has dedicated receptors for each taste, and that each class of receptors sends a specific signal to the brain. More recently, the team built on this by showing that in addition to dedicated receptors, there are unique sets of brain cells – each in different locations – that receive these signals. The red area below is the bitter neurons, and the aqua shows where the sweet brain cells are. 
 
 Charles Zucker/Columbia University Medical Centre 
 
 In this study, they decided to play with these brain cells and see if they could activate or deactivate them in order to trick mice into thinking they were tasting something sweet or bitter, without them actually tasting either. 
 
 "In this study, we wanted to know if specific regions in the brain really represent sweet and bitter. If they do, silencing these regions would prevent the animal from tasting sweet or bitter, no matter how much we gave them," said Zuker. "And if we activate these fields, they should taste bitter or sweet, even though they’re only getting plain water." 
 
 What they observed was exactly as they'd expected – when the sweet neurons were silenced using an injectable drug, the mice couldn't taste anything sweet, but they could still detect bitter flavours. 
 
 And when the researchers activated the sweet neurons using laser light, the mice tasted sweet flavours, even though they were only drinking plain water. The same thing happened when they stimulated or silenced the bitter brain cells. 
 
 The team was able to tell what the mice were tasting by their obvious reactions – they licked their lips when they tasted real or simulated sweet flavours, and gagged and looked disgusted when they tasted bitter. 
 
 To make sure what they were seeing was real, the researchers trained mice to perform certain behaviours when they tasted something sweet or bitter, and their behaviours didn't differ between the real and simulated tastes. The same thing even happened in animals that had never tasted either of the flavours before. 
 
 "These experiments formally prove that the sense of taste is completely hardwired, independent of learning or experience," said Zuker. 
 
 This discovery not only changes everything we knew about taste, but demonstrates that taste is different from the olfactory system because it's hardwired. 
 
 "Odours don’t carry innate meaning until you associate them with experiences. One smell could be great for you and horrible to me," added Zuker. But taste is already set. "In other words, taste is all in the brain." 
 
 The research has been published in Nature. ||||| Most people probably think that we perceive the five basic tastes—sweet, sour, salty, bitter and umami (savory)—with our tongue, which then sends signals to our brain “telling” us what we’ve tasted. However, scientists have turned this idea on its head, demonstrating in mice the ability to change the way something tastes by manipulating groups of cells in the brain. 
 
 The findings were published today in the online edition of Nature. 
 
 “Taste, the way you and I think of it, is ultimately in the brain,” said study leader Charles S. Zuker, PhD, professor of biochemistry and molecular biophysics and of neuroscience, a member of the Kavli Institute for Brain Science and the Mortimer B. Zuckerman Mind Brain Behavior Institute, and a Howard Hughes Medical Institute Investigator at Columbia University Medical Center (CUMC). “Dedicated taste receptors in the tongue detect sweet or bitter and so on, but it’s the brain that affords meaning to these chemicals.” 
 
 The primary aim of Dr. Zuker’s lab is to understand how the brain transforms detection of chemical stimuli into perception. Over the past decade or so, Dr. Zuker and his colleagues proved that there are dedicated receptors for each taste on the tongue, and that each class of receptor sends a specific signal to the brain. More recently, they demonstrated that each taste is sensed by unique sets of brain cells, located in separate locations in the brain’s cortex – generating a map of taste qualities in the brain. 
 
 The scientists used optogenetics, which allowed them to directly activate specific neurons with laser light. Yueqing Peng, a postdoctoral associate in Dr. Zuker’s lab, examined whether manipulating the neurons in these brain regions could evoke the perception of sweet or bitter, without the mouse actually tasting either. (Sweet and bitter tastes were chosen because they are most critical and recognizable tastes for humans and other animals. Sweet taste permits the identification of energy-rich nutrients, while bitter warns against the intake of potentially noxious chemicals.) 
 
 “In this study, we wanted to know if specific regions in the brain really represent sweet and bitter. If they do, silencing these regions would prevent the animal from tasting sweet or bitter, no matter how much we gave them,” he said. “And if we activate these fields, they should taste bitter or sweet, even though they’re only getting plain water.” 
 
 This is exactly what the researchers observed. When scientists injected a substance into the mice to silence the sweet neurons, the animals could not reliably identify sweet. They could, however, still detect bitter. The animals regained their ability to taste sweet when the drug was flushed from the brain. Conversely, silencing the bitter neurons prevented the mice from recognizing bitter, but they could still taste sweet. 
 
 Remarkably, the researchers were also able to make the animals think they were tasting bitter or sweet even when the animal was only drinking water. When the researchers activated the sweet neurons during drinking, they observed behavioral responses in the mice associated with sweet, such as impressively increased licking. In contrast, stimulating bitter neurons dramatically suppressed licking, and elicited classic taste-rejection responses, including the activation of gagging behavior. These results showed that by manipulating the brain centers representing sweet and bitter taste they could directly control an animal’s sensory perception and behavioral actions, says Peng. 
 
 The researchers also performed optogenetic tests on animals that had never tasted sweet or bitter chemicals, and showed that activation of the corresponding neurons triggered the appropriate behavioral response. “These experiments formally prove that the sense of taste is completely hardwired, independent of learning or experience,” said Dr. Zuker, “which is different from the olfactory system. Odors don’t carry innate meaning until you associate them with experiences. One smell could be great for you and horrible to me.” (As humans, of course, we can eventually learn to enjoy bitters and dislike sugar.) 
 
 In a final set of experiments, animals were trained to report the identity of an orally applied sweet and bitter stimulus by performing a novel behavioral task, allowing the researchers to test what the animal is tasting. In the experiments, the mice tasted real bitter, sweet, and salty chemicals at times, but at other times the researchers used the laser to activate the animals’ sweet or bitter cortical fields. The behavior of the mice did not differ between the real and virtual tastes, demonstrating that the light is mimicking the perception of bitter and sweet. “In other words, taste is all in the brain,” said Zuker. 
 
 About:
– That bitter tincture a bunch of mice in a Columbia University lab recently gagged on could have been sweet nectar, or even just plain water. Why they took issue with the taste: For a study published in the journal Nature, scientists fiddled with their brain cells to make them think they were sensing an entirely different taste—meaning taste may be nothing more than a "fragile illusion," as the Washington Post puts it. "Taste, the way you and I think of it, is ultimately in the brain," lead author Charles Zuker explains in a press release. He notes that while there are specific receptors on the tongue to pick up the five distinct tastes (sweet, sour, bitter, salty, and savory "umami"), the signals transmitted by each receptor are picked up by discrete sets of brain cells—cells that Zuker says can be effectively hacked to alter a subject's perception of a taste. And that's just what Zuker and his team did to the lab mice via optogenics, which uses the power of light to "selectively activate and deactivate the neurons associated with sweetness and bitterness," per the Post. Zuker compares it to pressing the keys of a piano: Press a certain key, get a certain sound. "But it doesn't matter how you press the key," he tells the Post. "You could use [a] finger, an elbow, a nose. It doesn't matter how we tweak the cells; if you tweak the right cells, you get the right signal." He says researchers saw that manifest in the lab when a mouse with a mouthful of water started gagging because scientists had "silenced" sweet-detecting neurons. "These experiments formally prove that the sense of taste is completely hardwired, independent of learning or experience," Zuker says, per ScienceAlert. Further research could eventually help people with eating and other disorders, he adds. And Zuker has even "sexier" goals in mind, per the Post. "If we could define the circuits involving courage, we could theoretically activate courage in the brain," he says. (Your lungs have taste buds, too, you know.)