Links for Keyword: Chemical Senses (Smell & Taste)

Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.


Links 81 - 100 of 429

By Katherine Harmon Weakening eyesight can be sharpened with lenses, and impaired hearing can be improved with aids. What about a failing sense of smell? Detecting and distinguishing the floral bouquet of fresh honey or the miasma of bad lunchmeat might not seem quite as critical for day-to-day existence as sight or hearing. But what the nose knows is clearly important for quality of life. Research has linked this diminution, which is common in people over the age of 60 and can be exacerbated by smoking and some diseases, to loss of appetite and even to depression. Now sufferers might not have to give in to an odorless future, according to a new study, published online Sunday in Nature Neuroscience. Researchers at the New York University Langone Medical Center have found that, with some simple training, over time lab rats could actually improve their brain’s ability to distinguish smells. Without any practice rats could tell when one scent—in a mélange of 10—had been switched for another. (Researchers figured this out by waiting until the rodents were thirsty, then training them to look for water in one of a selection of holes based on what odor combination they had detected.) But their powers of discrimination were not perfect. If a scent was missing from the mix, the rats did not seem to be able to discern it from a full 10-scent combination. Other rats, however, were trained to become extra-familiar with the different combinations through repeated exposures and rewards. “We made them connoisseurs,” co-author Donald Wilson, a professor of psychiatry at NYU Langone, said in a prepared statement. © 2011 Scientific American,

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 16072 - Posted: 11.22.2011

By Rachel Ehrenberg Scientists have finally explained how a little red berry makes just about anything, from the sourest lemon to the bitterest beer, taste as sweet as honey. A protein found in the fruit tickles the tongue’s sweet-sensing machinery, its effects intensifying in the presence of acidic flavors like citrus and carbonated drinks. Researchers and foodies alike have long known the effects of the miracle fruit (a.k.a. Richadella dulcifica). At flavor-tripping parties, guests will pop a berry then chew, chew and chew some more, letting the masticated fruit linger on the tongue. Then the sampling begins: Guinness tastes like a chocolate shake, Tabasco loses its sting and pickles their mouth-pinching tang. Lemons and limes gush with sweetness. While the active ingredient in miracle fruit — miraculin — has been known for decades, it hasn’t been clear exactly how the protein confers its sweetness. Now scientists in Japan and France report that miraculin’s interaction with the tongue’s sweet sensors depends on the acidity of the local environment. At a pH of 4.8 (water is neutral with a pH close to 7), the sweet-tasting cells respond twice as vigorously to miraculin than they do at a less acidic pH of 5.7. At closer-to-neutral pH levels of 6.7 and higher, the protein seems to slightly shift shape, blocking the sweet sensors but not activating them. This explains why under certain conditions sweet foods may taste less flavorful after eating the berry, researchers led by Keiko Abe of the University of Tokyo report online September 26 in the Proceedings of the National Academy of Sciences. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15853 - Posted: 09.29.2011

By Nick Bascom Even the inside of the nose can be a little cliquish. Like birds of a feather, nasal molecules that respond to pleasant smells flock together, keeping their distance from sensor molecules that pick up unpleasant smells. Sensor molecules, or receptors, appear to be organized according to the pleasantness (or unpleasantness) of the odors they sense, a new study finds. For example, locations in the nose that respond strongly to one fragrant aroma will respond strongly to other delectable smells. Patches of nasal surfaces that process putrid stenches also handle specific sorts of smells and leave the rest of the work to someone else, Noam Sobel of the Weizmann Institute of Science in Rehovot, Israel and colleagues reported online September 25 in Nature Neuroscience. The researchers inserted an electrode into 16 subjects’ noses and then showered the volunteers with six different scents. Because certain odors provoked stronger responses at different locations in the nose, the research team was able to confirm previous evidence suggesting a variegated nasal receptor surface. “We’re not the first to find that,” says Sobel. But he and his colleagues have added an important new wrinkle. “Not only are the receptors organized in patches, but the axis that best describes their organization is pleasantness.” This discovery sheds new light on a relatively poorly studied sensory organ. Compared with eyes or ears, scientists don’t know much about how the nose works. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 11: Emotions, Aggression, and Stress
Link ID: 15837 - Posted: 09.26.2011

By Jennifer Welsh, LiveScience Staff Writer Cats arch their backs at the smell of a rival, and mice scurry at the scent of a fox. But how does the nose know who or what is lurking? Now scientists have identified several special receptors in the noses of animals that react to specific scents given off by others. It's these receptors that signal to the brain whether the animal needs to flee, make itself large and scary, or perhaps even woo a mate. "Animals in the wild need to be able to recognize other animals, whether they are predators, potential mates or rivals," study researcher Catherine Dulac of Harvard University told LiveScience. "Many animals rely on the sense of smell; they can distinguish one type of encounter from another one based on chemicals." Experimenting on mice, Dulac and her fellow researchers discovered that more of the animal's receptors seem to be dedicated to sniffing out predators than to detecting potential mates. When a cat or mouse senses the chemical compounds secreted by other animals, it activates a special sensor in the nose called the vomeronasal organ. This organ, which is found in many animals and consists of a set of receptors, sends a signal to the brain, which interprets the signal and takes action. (Though humans have lost this organ, research has suggested humans do react in various ways to chemical cues.) © 2011 LiveScience.com

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15836 - Posted: 09.26.2011

By Susan Milius Penguins may be able to smell some feathery, waddling whiff of kinship on others of their kind. In some sniff tests, Humboldt penguins (Spheniscus humboldti) in the Brookfield Zoo outside Chicago could discriminate between the odor of birds they knew and birds they weren’t familiar with, says Jill Mateo of the University of Chicago. More intriguingly, the birds also showed evidence of an ability to distinguish between the scents of relatives and nonrelatives even if they weren’t personally familiar with the scent owners, Mateo and her colleagues report September 21 in PLoS ONE. The ability to recognize kin by smell has shown up in many other kinds of animals, including mammals, amphibians and fish. Although the new study is limited by its small size, it could be the first to show odor-based kinship recognition among birds. New evidence that a sense of smell may be important in birds also makes the study intriguing. For decades, scientists thought that most species of birds responded minimally, if at all, to odor cues. In recent years, though, researchers have uncovered more and more evidence for functionally significant sniffing, such as the odor detection of food out in the open ocean by blue petrels and some other tubenose seabirds. Odor-based kin recognition would make sense for colony-dwelling birds with lifetime monogamy such as the Humboldt penguins, which return to the same rookeries where they hatched in search of mating prospects. Birds hatched in different years by same parents could easily meet, Mateo says. “If familiarity is the only mechanism available to them, they might say, ‘Hey, I’m not related to you. Let’s have sex.” So a sniff test for kinship could come in handy. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15830 - Posted: 09.24.2011

by Catherine de Lange I TRY to forget about potential onlookers as I crawl around a central London park, blindfolded and on all fours. With a bit of luck, the casual passer-by might not notice the blindfold and think I'm just looking for a contact lens. In fact, I'm putting my sense of smell to the test, and attempting to emulate the sensory skills of a sniffer dog. Just as a beagle can swiftly hunt down a pheasant using only its nasal organ, I am using mine to follow a 10-metre trail of cinnamon oil. Such a challenge might sound doomed to failure. After all, dog noses are renowned for their sensitivity to smells, while human noses are poor by comparison. Yet that might be a misconception. According to a spate of recent studies, our noses are in fact exquisitely sensitive instruments that guide our everyday life to a surprising extent. Subtle smells can change your mood, behaviour and the choices you make, often without you even realising it. Our own scents, meanwhile, flag up emotional states such as fear or sadness to those around us. The big mystery is why we aren't aware of our nasal activity for more of the time. Noses have certainly never been at the forefront of sensory research, and were pushed aside until recently in favour of the seemingly more vital senses of vision and hearing. "There has been a lot of prejudice that people are not that influenced by olfactory stimuli, especially compared to other mammals," says Lilianne Mujica-Parodi, who studies the neurobiology of human stress at Stony Brook University in New York. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 11: Emotions, Aggression, and Stress
Link ID: 15821 - Posted: 09.20.2011

While the tongue map may have been thoroughly debunked, what about our brains? Does each kind of flavor get processed in its own little corner of our grey matter? According to new research, they just might. The image above is of the taste cortex (insula) of a mouse, with each of the color clumps representing one of four of the five primary tastes. Red is bitter, green is sweet, yellow is umami, and orange is salt. While the researchers also tested sour foods, they didn't spot a sour cluster, either because it was elsewhere in the brain or because sour food can also mess with pain pathways in the brain, as well as taste. What's interesting is how densely packed these taste hot spots are. Apparently, very few flavors cross over from one region to the other. In case you're curious what foods the researchers used as perfect examples of each taste type, they were: quinine and cycloheximide for bitter, sucrose and acesulfame potassium for sweet, MSG for umami, NaCl for salty and citric acid for sour. So, how long before we start hacking our brains to taste completely new flavors?

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15764 - Posted: 09.06.2011

by Caroline Williams Ever wondered how a dog, with a sense of smell that may be thousands of times more sensitive than ours, can bear to bury its face in the trash can? Alexandra Horowitz, a dog-cognition researcher at Columbia University in New York City and author of Inside of a Dog: What dogs see, smell, and know, says it's because the dog isn't simply smelling a stronger version of the revolting mono-stench that we smell. "It is not that smells are 'louder'," she says. "The smells have different layers, which probably give dogs a much bigger range of types of information." She compares it to the way we might enjoy a painting from across the room, but appreciate it in a different way when we can get up close and see the brush strokes. This makes a dog's experience fundamentally different to our own. When we go out for a walk, for example, we get almost all of our information from vision. But the dog's eyes are just a back-up. This was shown when police tracker dogs were given a scent trail that seemed to run in the opposite direction to a set of footprints on the ground; they invariably followed their noses and ignored the contradictory visual cues (Applied Animal Behaviour Science, vol 84, p 297). This reliance on smell explains why a dog that isn't expecting to see its owner will often stop a metre or so away for a quick sniff before jumping all over them. To imagine the scent-based world of a dog, says Horowitz, look around and imagine that everything you see has its own individual scent. And not just each object - different parts of the same object may hold different types of information. Horowitz gives the example of a rose: each petal might have a different scent, telling the dog it has been visited by different insects that left telltale traces of pollen from other flowers. Besides picking up on the individual scent of humans that had touched the flower, it could even guess when they may have passed by. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15721 - Posted: 08.25.2011

MacGregor Campbell, consultant Want to get rid of destructive lampreys? In this video, you can see how the smell of death can be a particularly effective repellant. Michael Wagner of Michigan State University exposed a group of lampreys to a mixture of chemicals from putrefying carcasses and ethanol. Another group was subjected to a similar amount of plain ethanol as a control. The animals exposed to the death-scented chemicals jumped out of the tank with a panic-like response. Sea lampreys are an invasive species in the US Great Lakes. They live as parasites on the bodies of lake trout and other commercially-important fish and have contributed to collapsing fish stocks in the region. Currently, wildlife officials use pheromones to lure lampreys into large cages where they can be destroyed or sterilised. These are the same chemicals the lampreys rely on to attract mates or to find good spawning grounds. But using natural cues to attract lampreys can be inefficient since a variety of scents in natural waterways compete for their attention. According to Wagner, repellants could be a better alternative to divert them since even tiny quantities can provoke a response. The smell of death could be used to form a chemical dam to steer lampreys away from environmentally-sensitive waterways. The chemicals could also be used to corral the animals into groups, making them easier to eliminate. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15719 - Posted: 08.25.2011

By Laura Sanders A common virus may slink into the brain through the nose. After setting up shop in people’s nasal mucus, human herpesvirus-6 may travel along olfactory cells right into the brain, researchers report online the week of August 8 in the Proceedings of the National Academy of Sciences. Most people’s first bout with HHV-6 comes at a tender age: It causes the common childhood infection roseola, marked by a chest rash and a high fever. “Everyone is exposed to this,” says study coauthor Steven Jacobson of the National Institute of Neurological Disorders and Stroke in Bethesda, Md. “You have it. I have it.” Despite its ubiquity, very little is known about the virus. HHV-6 may live in tonsils and shed in saliva, some studies suggest. And in some people (researchers don’t know how many), the virus can infect the brain, where some researchers believe it may contribute to neurological disorders such as multiple sclerosis, encephalitis and a form of epilepsy. Other viruses such as herpes simplex, influenza A and rabies can invade the brain by shooting through the nose, so Jacobson and his team wondered whether HHV-6 could do the same trick. The researchers found high levels of HHV-6 in the olfactory bulb, a smell-related part of the brain, in two of three autopsy brain samples. The team then looked at nose mucus and found the virus in 52 of 126 different samples. “We were surprised to find so much in the nasal mucus,” Jacobson says. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 2: Functional Neuroanatomy: The Nervous System and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 2: Cells and Structures: The Anatomy of the Nervous System
Link ID: 15658 - Posted: 08.09.2011

By Karen Weintraub Out for a run six years ago, Molly Birnbaum was struck by a car. Recovering from surgeries to repair a broken pelvis and torn tendons, she realized the blow had also left her completely unable to smell. Then a recent college graduate and aspiring chef, Birnbaum said it was as if all the color drained out of life. Without the scent of roses, fresh bread, a spring rain, or even trash, she felt like she was living in a black and white world. Estimates are that 1-2 percent of Americans under 65 have a limited sense of smell; that percentage rises to as high as 50 percent of those over 65. And doctors are just beginning to realize how important smell is to our well-being and our perceptions of the world. “Your nose, sitting there in the middle of your face, is arguably the best chemical detector on the planet, but we usually fail to realize its importance until it goes missing due to illness or injury,’’ said Stuart Firestein, a scientist who studies the sense of smell, and the chairman of the biological sciences department at Columbia University. Research into the olfactory process has increased dramatically in recent years, with the first smell-related Nobel Prize awarded in 2004, to an American team; the discovery that smell plays a role in some brain disorders; and the hope that a better understanding of smell may offer insights into how the brain works. © 2011 NY Times Co.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15576 - Posted: 07.19.2011

Nicola Nosengo If you are a small animal, it is useful to know whether there is anything around that might want to eat you. Stephen Liberles from Harvard Medical School in Cambridge, Massachusetts, and his colleagues have analysed urine samples from a variety of zoo inhabitants, including lions and bears, and discovered how rodents can use smell to do just that. In a research published today in the Proceedings of the National Academy of Science, the team identifies a chemical found in high concentrations in the urine of carnivores that makes mice and rats run for cover1. Chemicals have already been identified that allow prey to recognize a known predator. But this is the first example of a generic clue that allows an animal to detect any potential predator, irrespective of whether the two species have ever come into contact. The researchers started by analysing an engimatic group of olfactory receptors discovered in 2001 called trace amine-associated receptors (TAARs)2. They are found in most vertebrates, in varying numbers. Mice, for example, have 15, rats 17 and humans have just 6. Very little is known about what chemicals bind to them. Liberles and his colleagues found that one member of the receptor family, TAAR4, is strongly activated by bobcat urine, which is sold online and used by gardeners to keep rodents and rabbits away. They managed to extract the molecule responsible for activating the receptor, called 2-phenylethylamine. © 2011 Nature Publishing Group,

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 11: Emotions, Aggression, and Stress
Link ID: 15468 - Posted: 06.21.2011

By Jennifer Welsh WASHINGTON — Suit pressed, mind ready and resume in hand. When preparing for a job interview, most people take every precaution to convey the best impression possible. But aside from body odor, not many people pay attention to the odors that surround them. That onion-laden lunch could give your potential boss-to-be the wrong impression, according to new research presented in May at the Association for Psychological Science annual meeting. "There's a lot of research that's begun now, where people are looking at how the environment affects our well-being," said Jeannette Haviland-Jones, of Rutgers University in New Jersey. "We tend to think of ourselves as separate from the environment, but we're not. We create our environment." Hers and others' research is showing that smell can influence our thoughts and behaviors more expected. Many things in the environment, including verbal and physical cues, can influence how we perceive others. New research presented by Nicole Hovis and Theresa White of Le Moyne College in Syracuse, N.Y., shows that certain smells can influence a first impression. They asked 65 volunteer undergraduates (who were mostly female) to sniff a vial holding either a lemon or onion scent, or no scent, while standing near a gender-neutral silhouette. They were asked to form an impression of the personality of the silhouette and later filled out a form rating several personality traits. © 2011 LiveScience.com

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15461 - Posted: 06.20.2011

By NICHOLAS BAKALAR Ants called Pseudomyrmex triplarinus live inside the leaves and trunk of Triplaris americana trees, where they take shelter and eat sugars, fats and proteins supplied by the tree. In return, they bite animals that try to eat the trees’ leaves, and they prune away plants that grow near them. Now researchers have figured out one way in which they can distinguish a foreign plant from their own. A study showed that Pseudomyrmex triplarinus ants were able to recognize extract from different types of trees independent of the shape or texture of the material that carried it. The scientists, working in Peru, found that the ants consistently pruned foreign seedlings that sprouted near their tree. They also removed 80 to 100 percent of foreign leaves experimentally pinned to the trunk, compared with only 10 to 30 percent of T. americana leaves. Then the investigators treated identical strips of filter paper with leaf wax extracts from T. americana; with extracts from T. poeppigiana, a closely related species; or with plain solvents as a control. The ants attacked the control strips more often than the T. poeppigiana, and the T. poeppigiana more often than the T. americana strips. This suggests the ants could, to a significant degree, recognize the extract independent of the shape or texture of the material that carried it. © 2011 The New York Times Company

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15327 - Posted: 05.14.2011

By Bonnie Berkowitz, Black coffee. Hot peppers. Truffles. Oysters. The world is full of polarizing flavors and foods, beloved by many, despised by just as many. Why is that? Scientists have untangled some — but not nearly all — of the mysteries behind our love and hatred of certain foods. While we might say, “That tastes like strawberry,” scientists who study these things would disagree. Our tongues actually perceive only five basic tastes: sweet, sour, bitter, salty and “umami,” the Japanese word for savory. To go from merely sweet to “Mmm, strawberry!” the nose has to get involved. The taste and olfactory senses, along with any chemical irritation a food creates in the throat (think mint, hot pepper or olive oil), all send the brain the information it needs to distinguish flavors. “We as primates are born liking sweet and disliking bitter,” said Marcia Pelchat, who studies food preferences at the Monell Chemical Senses Center in Philadelphia. The theory is that we’re hard-wired to like and dislike certain basic tastes so that the mouth can act as the body’s gatekeeper. Sweet means energy; sour means not ripe yet. Savory means food may contain protein. Bitter means caution, as many poisons are bitter. Salty means sodium, a necessary ingredient for several functions in our bodies. (By the way, those tongue maps that show taste buds clumped into zones that detect sweet, bitter, etc.? Very misleading. Taste receptors of all types blanket our tongues — except for the center line — and some reside elsewhere in our mouths and throats.)

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15269 - Posted: 04.28.2011

By Steve Mirsky All seemed well that morning when the rains came. I was warm and dry and didn’t need to leave the comfort of home. But that comfort swiftly departed. First, I heard the glug glug glug. Then I picked up a whiff both faint and foul. Something was entering the bathroom that should only exit the bathroom—raw sewage was reversing its natural course and fighting its way back into my house. The whiffs got stronger. Human waste includes some fascinating and fragrant organic compounds. Take skatole. (Please.) Skatole bears a heavy responsibility for making poo smell phooey. But remember the axiom: it’s the dose that makes the poison. Because in low concentrations, according to Wikipedia, skatole “has a flowery smell and is found in several flowers and essential oils,” such as orange blossoms and jasmine. It is even used—again, in very small amounts—in perfumes. Think about that when dabbing behind the ears. And Wikipedia notes that cigarette manufacturers add skatole as (drum roll) a flavoring ingredient. Just another reason to stop smoking. In addition, waste contains various stinky sulfur compounds, collectively called thiols or mercaptans. They are not your friends. When sewage is backing up into one’s home, the to-do list instantly becomes an un-doo list with only one item: get the plumbers to come immediately. Upon their swift arrival, they unsealed the trap to gain access to the line, which also sent the incoming waste fluid into the subbasement—still bad, but a big improvement. They then sent a camera down the line to examine the problem, performing their version of the closely related diagnostic technique of colonoscopy. © 2011 Scientific American,

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15257 - Posted: 04.23.2011

(HealthDay News) -- A hormone called ghrelin enhances the nose's ability to sniff out food, researchers report. It was already known that ghrelin promotes hunger and fat storage. The new study suggests that the hormone may increase the ability to use smell to detect food and link that input with the body's natural regulation of metabolism and body weight, said University of Cincinnati scientists. Click here to find out more! The study, which included experiments with humans and rats, appears in the April 13 issue of the Journal of Neuroscience. It was led by Dr. Jenny Tong and Dr. Matthias Tschop, both of the university's endocrinology, diabetes and metabolism division. "Smell is an integral part of feeding, and mammals frequently rely on smell to locate food and discriminate among food sources. Sniffing is the first stage of the smell process and can enhance odor detection and discrimination," Tong said in a university news release. "Other studies have shown that hunger can enhance odor detection and sniffing in animals," Tschop added in the release. "Since ghrelin is a hunger-inducing stomach hormone that is secreted when the stomach is empty, this hormone pathway may also be responsible for the hunger-induced enhancement of sniffing and odor detection." The researchers plan further research to identify the exact molecular pathways through which ghrelin affects sniff behavior. © 2011 HealthDay.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 15209 - Posted: 04.14.2011

by Rachel Courtland How does a nose generate the signals that the brain registers as smell? The conventional theory says it's down to the different shapes of smelly molecules. But fruit flies have now distinguished between two molecules with identical shapes, providing the first experimental evidence to support a controversial theory that the sense of smell can operate by detecting molecular vibrations. The noses of mammals, and the antennae of flies, are lined with different folded proteins that form pocket-shaped "receptors". It has been generally assumed that a smell arises when an odour molecule slides into a receptor like a key in a lock, altering the receptor's shape and triggering a cascade of chemical events that eventually reach the brain. But this "shape" theory has limitations. For one, it can't easily explain why different molecules can have very similar smells. In 1996, Luca Turin, a biophysicist now at the Massachusetts Institute of Technology, proposed a solution. He revived a theory that the way a molecule vibrates can dictate it odour, and came up with a mechanism to explain how this might work. His idea was that electrons might only be able to pass across a receptor if it was bound to a molecule that vibrated at just the right frequency. Ordinarily, the energy needed for the electron to make this journey would be too great, but the right vibrational energy could prompt a quantum effect in which the electron "tunnels" through this energy barrier, and this would then be detected and registered as a particular smell (see diagram). © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 15001 - Posted: 02.15.2011

by Kirsten Weir 1 Remember the tongue map you learned about in junior high—the one showing taste receptors for sweet flavors on the tip of the tongue, bitter in the back, and sour on the sides? It’s totally wrong. 2 That bogus map came from an English mistranslation of a German research paper. 3 In truth, any area can pick up any taste (although sensitivity does vary across the tongue). 4 We all know about sweet, salty, sour, and bitter. Less widely known is the fifth taste: umami, that savory flavor of soy sauce, tomatoes, and many other foods high in glutamate. 5 Go with your gut: Japanese scientists recently identified umami receptors not only on the tongue but throughout the digestive tract. Their role in digestion and nutrition remains a mystery. 6 Those bumps on your tongue aren’t actually your taste buds. They are fungiform papillae—“mushroom-shaped nipples,” to any Latin speakers out there—and each houses 50 to 100 buds. 7 Scientists believe there are only a few receptor types each for sweet, sour, salty, and umami. But there are a lot more for bitter (at least 25), as anyone paying alimony is probably aware. © 2011, Kalmbach Publishing Co.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 14989 - Posted: 02.12.2011

In 2004, American neuroscientists Linda Buck and Richard Axel shared a Nobel Prize for their identification of the genes that control smell, findings which they first published in the early 1990s. Their work revived interest in the mysterious workings of our noses, interest which is now generating some surprising insights – not least that each of us inhabits our own, personal olfactory world. "When I give talks, I always say that everybody in this room smells the world with a different set of receptors, and therefore it smells different to everybody," says Andreas Keller, a geneticist working at the Rockefeller University in New York City. He also suspects that every individual has at least one odorant he or she cannot detect at all – one specific anosmia, or olfactory "blind spot", which is inherited along with his or her olfactory apparatus. The human nose contains roughly 400 olfactory receptors, each of which responds to several odorants, and each of which is encoded by a different gene. But, says Boris Schilling, a biochemist working for Givaudan, the world's largest flavour and fragrance company, based in Geneva, Switzerland, "unless you are dealing with identical twins, no two persons will have the same genetic make-up for those receptors." The reason, according to Doron Lancet, a geneticist at the Weizmann Institute of Science in Israel, is that those genes have been accumulating mutations over evolution. This has happened in all the great apes, and one possible explanation is that smell has gradually become less important to survival, having been replaced to some extent by colour vision – as an indicator of rotten fruit, for example, or of a potentially venomous predator. ©independent.co.uk

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 14906 - Posted: 01.24.2011