Links for Keyword: Chemical Senses (Smell & Taste)

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By Winston Choi-Schagrin SOUTH ST. PAUL, Minn. — Chuck McGinley, a chemical engineer, stepped out of his car, eyed the smokestack of an animal processing plant rising above the treetops, and inhaled deeply. At first he smelled nothing except the faint, sweet fragrance of the nearby trees. Suddenly, the wind picked up. “We have an oh-my-God smell!” Mr. McGinley exclaimed. Immediately one of his colleagues pressed a Nasal Ranger to his nose. The 14-inch-long smell-measuring device, which looks like a cross between a radar gun and a bugle, is one of Mr. McGinley’s most significant inventions. Using terms from one of Mr. McGinley’s other standard tools, an odor wheel, a chart akin to an artist’s color wheel that he has been fine-tuning for decades, the team described the stink. “Sour,” one person said. “Decay, with possibly some petroleum,” said another. Then, as quickly as it had arrived, the smell disappeared. “The wind decided it was going to gift us only a short sniff,” Mr. McGinley said. “To tease us.” Intuitively, humans know to avoid bad smells. Yet for a half-century, Mr. McGinley, 76, has returned again and again to society’s stinkiest sites, places very much like this one, in order to measure, describe and demystify smell. Climate Fwd There’s an ongoing crisis — and tons of news. Our newsletter keeps you up to date. Get it sent to your inbox. From his unconventional lab in a Minnesota suburb (it actually feels more like a ski lodge) Mr. McGinley and his son Mike have established an outsize influence over the measurement and understanding of odor. They have equipped scientists around the world with tools the elder Mr. McGinley invented, advised governments on odor regulations and empowered communities near smelly places to find a vocabulary for their complaints and a way to measure what their noses are telling them. In many ways, the growing demand for Mr. McGinley’s services and instruments signals society’s heightened awareness of the power of odor and its potential to make people physically ill or diminish their quality of life. His inventions have taken on a powerful role in a movement to recognize odor as a pollutant, not merely an annoyance, worthy of closer study and perhaps tighter regulation. © 2022 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28153 - Posted: 01.15.2022

By Judith Graham The reports from coronavirus patients are disconcerting. Only a few hours before, they were enjoying a cup of pungent coffee or the fragrance of flowers in a garden. Then, as if a switch had been flipped, those smells disappeared. F Young and old alike are affected — more than 80 to 90 percent of those diagnosed with the virus, according to some estimates. While most people recover in a few months, 16 percent take half a year or longer to do so, research has found. According to new estimates, up to 1.6 million Americans have chronic smell problems because of covid-19, the disease caused by the coronavirus. Seniors are especially vulnerable, experts say. “We know that many older adults have a compromised sense of smell to begin with. Add to that the insult of covid, and it made these problems worse,” said Jayant Pinto, a professor of surgery and a specialist in sinus and nasal diseases at the University of Chicago Medical Center. Advertisement Recent data highlights the interaction between covid-19, advanced age and loss of smell. When Italian researchers evaluated 101 patients who had been hospitalized for mild to moderate covid-19, 50 showed objective signs of smell impairment six months later. Those 65 or older were nearly twice as likely to be impaired; those 75 or older were more than 2½ times as likely. Most people aren’t aware of the extent to which smell can be diminished in later life. More than half of 65-to-80-year-olds have some degree of smell loss, or olfactory dysfunction, as it’s known in the scientific literature. That rises to as high as 80 percent for those even older. People affected often report concerns about safety, less enjoyment eating and an impaired quality of life. But because the ability to detect, identify and discriminate among odors declines gradually, most older adults — up to 75 percent of those with some degree of smell loss — don’t realize they’re affected.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28151 - Posted: 01.12.2022

Stephen Wooding The sweetness of sugar is one of life’s great pleasures. People’s love for sweet is so visceral, food companies lure consumers to their products by adding sugar to almost everything they make: yogurt, ketchup, fruit snacks, breakfast cereals and even supposed health foods like granola bars. Schoolchildren learn as early as kindergarten that sweet treats belong in the smallest tip of the food pyramid, and adults learn from the media about sugar’s role in unwanted weight gain. It’s hard to imagine a greater disconnect between a powerful attraction to something and a rational disdain for it. How did people end up in this predicament? I’m an anthropologist who studies the evolution of taste perception. I believe insights into our species’ evolutionary history can provide important clues about why it’s so hard to say no to sweet. The basic activities of day-to-day life, such as raising the young, finding shelter and securing enough food, all required energy in the form of calories. Individuals more proficient at garnering calories tended to be more successful at all these tasks. They survived longer and had more surviving children – they had greater fitness, in evolutionary terms. One contributor to success was how good they were at foraging. Being able to detect sweet things – sugars – could give someone a big leg up. In nature, sweetness signals the presence of sugars, an excellent source of calories. So foragers able to perceive sweetness could detect whether sugar was present in potential foods, especially plants, and how much. © 2010–2022, The Conversation US, Inc.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28146 - Posted: 01.12.2022

By Ariana Remmel Scientists have finally sniffed out the molecules behind marijuana’s skunky aroma. The heady bouquet that wafts off of fresh weed is actually a cocktail of hundreds of fragrant compounds. The most prominent floral, citrusy and piney overtones come from a common class of molecules called terpenes, says analytical chemist Iain Oswald of Abstrax Tech, a private company in Tustin, Calif., that develops terpenes for cannabis products (SN: 4/30/18). But the source of that funky ganja note has been hard to pin down. Now, an analysis is the first to identify a group of sulfur compounds in cannabis that account for the skunklike scent, researchers report November 12 in ACS Omega. Oswald and colleagues had a hunch that the culprit may contain sulfur, a stinky element found in hops and skunk spray. So the team started by rating the skunk factor of flowers harvested from more than a dozen varieties of Cannabis sativa on a scale from zero to 10, with 10 being the most pungent. Next, the team created a “chemical fingerprint” of the airborne components that contributed to each cultivar’s unique scent using gas chromatography, mass spectroscopy and a sulfur chemiluminescence detector. As suspected, the researchers found small amounts of several fragrant sulfur compounds lurking in the olfactory profiles of the smelliest cultivars. The most dominant was a molecule called prenylthiol, or 3-methyl-2-butene-1-thiol, that gives “skunked beer” its notorious flavor (SN: 11/27/05). © Society for Science & the Public 2000–2021

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 4: Development of the Brain
Link ID: 28092 - Posted: 12.01.2021

ByEmily Underwood Scientists have argued for decades over whether humans have pheromones, chemical compounds that trigger aggression and mating in insects and other animals. Although the notion has great popular appeal—search Amazon for “pheromone” and you’ll get the idea—there’s scant evidence for this kind of signal in our species. A new study could change that. Researchers have identified an odorless compound emitted by people—and in particular babies—called hexadecanal, or HEX, that appears to foster aggressive behavior in women and blunt it in men. “We cannot say that this is a pheromone,” says study author Noam Sobel, a neuroscientist at the Weizmann Institute of Science. “But we can say that it’s a molecule expressed by the human body that influences human behavior, specifically aggressive behavior, in a predicted manner.” Humans emit HEX from their skin, saliva, and feces, and it’s among the most abundant molecules babies emit from their heads. When researchers isolated the odorless compound and piped it into mouse cages, it had a relaxing effect on the animals, says Sobel, who studies the role of scent in human interactions. To test how HEX affects people, Eva Mishor, who earned her Ph.D. in Sobel’s lab, created a series of computer games designed to evoke intense frustration—and a measurable response to it—in 126 human participants. Half of the volunteers wore a HEX-infused adhesive strip on their upper lips while they played, whereas the other half wore strips that smelled identical but were HEX-free. In one task, participants negotiated with an unseen partner to divvy up a sum of virtual money. The participants thought they were playing with another person, but they were actually playing against computers. If a player offered their “partner” anything less than 90% of the whole amount, the computer rejected their proposals with a bright red “NO!” preventing them from earning any money. © 2021 American Association for the Advancement of Science.

Related chapters from BN: Chapter 9: Hearing, Balance, 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: 28086 - Posted: 11.20.2021

Abby Olena Most people enjoy umami flavor, which is perceived when a taste receptor called T1R1/T1R3 senses the amino acid glutamate. In some other mammals, such as mice, however, this same receptor is much less sensitive to glutamate. In a new study published August 26 in Current Biology, researchers uncover the molecular basis for this difference. They show that the receptor evolved in humans and some other primates away from mostly binding free nucleotides, which are common in insects, to preferentially binding glutamate, which is abundant in leaves. The authors argue that the change facilitated a major evolutionary shift in these primates toward a plant-heavy diet. “The question always comes up about the evolution of umami taste: In humans, our receptor is narrowly tuned to glutamate, and we never had a good answer for why,” says Maude Baldwin, a sensory biologist at the Max Planck Institute for Ornithology in Germany. She was not involved in the new work, but coauthored a 2014 study with Yasuka Toda, who is also a coauthor on the new paper, showing that the T1R1/T1R3 receptor is responsible for sweet taste in hummingbirds. In the new study, the authors find “that this narrow tuning has evolved convergently multiple times [and] that it’s related to folivory,” she says, calling the paper “a hallmark, fantastic study, and one that will become a textbook example of how taste evolution can relate to diet and how to address these types of questions in a rigorous, comprehensive manner.” © 1986–2021 The Scientist.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28037 - Posted: 10.16.2021

Abby Olena Most people enjoy umami flavor, which is perceived when a taste receptor called T1R1/T1R3 senses the amino acid glutamate. In some other mammals, such as mice, however, this same receptor is much less sensitive to glutamate. In a new study published August 26 in Current Biology, researchers uncover the molecular basis for this difference. They show that the receptor evolved in humans and some other primates away from mostly binding free nucleotides, which are common in insects, to preferentially binding glutamate, which is abundant in leaves. The authors argue that the change facilitated a major evolutionary shift in these primates toward a plant-heavy diet. “The question always comes up about the evolution of umami taste: In humans, our receptor is narrowly tuned to glutamate, and we never had a good answer for why,” says Maude Baldwin, a sensory biologist at the Max Planck Institute for Ornithology in Germany. She was not involved in the new work, but coauthored a 2014 study with Yasuka Toda, who is also a coauthor on the new paper, showing that the T1R1/T1R3 receptor is responsible for sweet taste in hummingbirds. In the new study, the authors find “that this narrow tuning has evolved convergently multiple times [and] that it’s related to folivory,” she says, calling the paper “a hallmark, fantastic study, and one that will become a textbook example of how taste evolution can relate to diet and how to address these types of questions in a rigorous, comprehensive manner.” In 2011, Toda, who was then at the University of Tokyo and now leads a group at Meiji University in Japan, and Takumi Misaka of the University of Tokyo developed a strategy to use cultured cells to analyze the function of taste receptors. They used the technique to tease out the parts of the human T1R1/T1R3 that differed from that of mice and thus underlie the high glutamate sensitivity in the human receptor, work that they published in 2013. © 1986–2021 The Scientist.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27986 - Posted: 09.13.2021

Michael Marshall Since the beginning of the pandemic, researchers have been trying to understand how the coronavirus SARS-CoV-2 affects the brain.Credit: Stanislav Krasilnikov/TASS/Getty How COVID-19 damages the brain is becoming clearer. New evidence suggests that the coronavirus’s assault on the brain could be multipronged: it might attack certain brain cells directly, reduce blood flow to brain tissue or trigger production of immune molecules that can harm brain cells. Infection with the coronavirus SARS-CoV-2 can cause memory loss, strokes and other effects on the brain. The question, says Serena Spudich, a neurologist at Yale University in New Haven, Connecticut, is: “Can we intervene early to address these abnormalities so that people don’t have long-term problems?” With so many people affected — neurological symptoms appeared in 80% of the people hospitalized with COVID-19 who were surveyed in one study1 — researchers hope that the growing evidence base will point the way to better treatments. Breaking into the brain SARS-CoV-2 can have severe effects: a preprint posted last month2 compared images of people’s brains from before and after they had COVID-19, and found loss of grey matter in several areas of the cerebral cortex. (Preprints are published without peer review.) Early in the pandemic, researchers speculated that the virus might cause damage by somehow entering the brain and infecting neurons, the cells responsible for transmitting and processing information. But studies have since indicated3 that the virus has difficulty getting past the brain’s defence system — the blood–brain barrier — and that it doesn’t necessarily attack neurons in any significant way.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 12: Psychopathology: The Biology of Behavioral Disorders
Link ID: 27899 - Posted: 07.08.2021

By Elizabeth Pennisi Almost 200 years ago, the renowned U.S. naturalist John James Audubon hid a decaying pig carcass under a pile of brush to test vultures’ sense of smell. When the birds overlooked the pig—while one flocked to a nearly odorless stuffed deer skin—he took it as proof that they rely on vision, not smell, to find their food. His experiment cemented a commonly held idea. Despite later evidence that vultures and a few specialized avian hunters use odors after all, the dogma that most birds aren’t attuned to smell endured. Now, that dogma is being eroded by findings on birds’ behavior and molecular hardware, two of which were published just last month. One showed storks home in on the smell of freshly mowed grass; another documented scores of functional olfactory receptors in multiple bird species. Researchers are realizing, says evolutionary biologist Scott Edwards of Harvard University, that “olfaction has a lot of impact on different aspects of bird biology.” Forty years ago, when ethologist Floriano Papi proposed that homing pigeons find their way back to a roost by sniffing out its chemical signature, his colleagues scoffed at the idea. They pointed out that birds have several other keen senses to guide them, including sight and, in the case of pigeons and some other species, a magnetic sense. “By then, biological textbooks already stated unequivocally that birds have little to no sense of smell, and many people still believe it—even scientists,” says Danielle Whittaker, a chemical ecologist at Michigan State University. © 2021 American Association for the Advancement of Science.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27897 - Posted: 07.08.2021

Kurt Schwenk As dinosaurs lumbered through the humid cycad forests of ancient South America 180 million years ago, primeval lizards scurried, unnoticed, beneath their feet. Perhaps to avoid being trampled by their giant kin, some of these early lizards sought refuge underground. Here they evolved long, slender bodies and reduced limbs to negotiate the narrow nooks and crevices beneath the surface. Without light, their vision faded, but to take its place, an especially acute sense of smell evolved. It was during this period that these proto-snakes evolved one of their most iconic traits – a long, flicking, forked tongue. These reptiles eventually returned to the surface, but it wasn’t until the extinction of dinosaurs many millions of years later that they diversified into myriad types of modern snakes. As an evolutionary biologist, I am fascinated by these bizarre tongues – and the role they have played in snakes’ success. Snake tongues are so peculiar they have fascinated naturalists for centuries. Aristotle believed the forked tips provided snakes a “twofold pleasure” from taste – a view mirrored centuries later by French naturalist Bernard Germain de Lacépède, who suggested the twin tips could adhere more closely to “the tasty body” of the soon-to-be snack. A 17th-century astronomer and naturalist, Giovanni Battista Hodierna, thought snakes used their tongues for “picking the dirt out of their noses … since they are always grovelling on the ground.” Others contended the tongue captured flies “with wonderful nimbleness … betwixt the forks,” or gathered air for sustenance.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27876 - Posted: 06.26.2021

Jordana Cepelewicz Smell, rather than sight, reigns as the supreme sense for most animals. It allows them to find food, avoid danger and attract mates; it dominates their perceptions and guides their behavior; it dictates how they interpret and respond to the deluge of sensory information all around them. “How we as biological creatures interface with chemistry in the world is profoundly important for understanding who we are and how we navigate the universe,” said Bob Datta, a neurobiologist at Harvard Medical School. Yet olfaction might also be the least well understood of our senses, in part because of the complexity of the inputs it must reckon with. What we might label as a single odor — the smell of coffee in the morning, of wet grass after a summer storm, of shampoo or perfume — is often a mixture of hundreds of types of chemicals. For an animal to detect and discriminate between the many scents that are key to its survival, the limited repertoire of receptors on its olfactory sensory neurons must somehow recognize a vast number of compounds. So an individual receptor has to be able to respond to many diverse, seemingly unrelated odor molecules. That versatility is at odds with the traditional lock-and-key model governing how selective chemical interactions tend to work. “In high school biology, that’s what I learned about ligand-receptor interactions,” said Annika Barber, a molecular biologist at Rutgers University. “Something has to fit precisely in a site, and then it changes the [protein’s atomic arrangement], and then it works.” All Rights Reserved © 2021

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27869 - Posted: 06.23.2021

By Deborah Schoch Marcel Kuttab first sensed something was awry while brushing her teeth a year ago, several months after recovering from Covid-19. Her toothbrush tasted dirty, so she threw it out and got a new one. Then she realized the toothpaste was at fault. Onions and garlic and meat tasted putrid, and coffee smelled like gasoline — all symptoms of the once little-known condition called parosmia that distorts the senses of smell and taste. Dr. Kuttab, 28, who has a pharmacy doctoral degree and works for a drug company in Massachusetts, experimented to figure out what foods she could tolerate. “You can spend a lot of money in grocery stores and land up not using any of it,” she said. The pandemic has put a spotlight on parosmia, spurring research and a host of articles in medical journals. Membership has swelled in existing support groups, and new ones have sprouted. A fast-growing British-based Facebook parosmia group has more than 14,000 members. And parosmia-related ventures are gaining followers, from podcasts to smell training kits. Yet a key question remains unanswered: How long does Covid-linked parosmia last? Scientists have no firm timelines. Of five patients interviewed for this article, all of whom first developed parosmia symptoms in late spring and early summer of last year, none has fully regained normal smell and taste. Brooke Viegut, whose parosmia began in May 2020, worked for an entertainment firm in New York City before theaters were shuttered. She believes she caught Covid in March during a quick business trip to London, and, like many other patients, she lost her sense of smell. Before she regained it completely, parosmia set in, and she could not tolerate garlic, onions or meat. Even broccoli, she said at one point earlier this year, had a chemical smell. She still can’t stomach some foods, but she is growing more optimistic. “A lot of fruits taste more like fruit now instead of soap,” she said. And she recently took a trip without getting seriously nauseous. “So, I’d say that’s progress.” © 2021 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, 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: 27857 - Posted: 06.16.2021

Ed Yong Carl Schoonover and Andrew Fink are confused. As neuroscientists, they know that the brain must be flexible but not too flexible. It must rewire itself in the face of new experiences, but must also consistently represent the features of the external world. How? The relatively simple explanation found in neuroscience textbooks is that specific groups of neurons reliably fire when their owner smells a rose, sees a sunset, or hears a bell. These representations—these patterns of neural firing—presumably stay the same from one moment to the next. But as Schoonover, Fink, and others have found, they sometimes don’t. They change—and to a confusing and unexpected extent. Schoonover, Fink, and their colleagues from Columbia University allowed mice to sniff the same odors over several days and weeks, and recorded the activity of neurons in the rodents’ piriform cortex—a brain region involved in identifying smells. At a given moment, each odor caused a distinctive group of neurons in this region to fire. But as time went on, the makeup of these groups slowly changed. Some neurons stopped responding to the smells; others started. After a month, each group was almost completely different. Put it this way: The neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time. This is, of course, just one study, of one brain region, in mice. But other scientists have shown that the same phenomenon, called representational drift, occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery. Schoonover and Fink told me that they don’t know why it happens, what it means, how the brain copes, or how much of the brain behaves in this way. How can animals possibly make any lasting sense of the world if their neural responses to that world are constantly in flux? (c) 2021 by The Atlantic Monthly Group

Related chapters from BN: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27852 - Posted: 06.11.2021

Joanne Silberner Scientists once compared the abilities of humans versus canines in tracking a trail of chocolate essential oil laid down in an open field. Though the humans weren't nearly as proficient as the dogs, they did get better with practice. Vladimir Godnik/Getty Images/fStop About 25 years ago, after a particularly bad cold, I suddenly lost my sense of smell — I could no longer sense the difference between sweaty tennis shoes and a fragrant rose. Since then, my olfactory discernment comes and goes, and most of the time it's just gone. I always figured there wasn't much I could do about that, and it hasn't been terrible. My taste buds still work, and I adore fine chocolate. But when COVID-19 hit, the inability to detect odors and fragrances became a diagnostic symptom that upset a lot of COVID-19 sufferers, many of whom also lost their sense of taste. That got me thinking — what does it really mean to have a disordered sense of smell? Does it matter that with my eyes closed I can't tell if I'm in an overripe gym or a perfume store? And is there hope that I'll ever again be able to smell a wet dog or freesia or a gas leak or a raw onion? Scientists explain that when you put your nose in the way of steam rising from a hot cup of coffee, molecules called odorants rise up and land high up in your nose. And when you take a swig of that same joe, as the liquid goes down your throat, some molecules rise upward and hit that sweet spot. Nerve cells there have receptors that recognize specific molecules, and those nerve cells extend directly into the brain. "That's how you tell you're smelling coffee as opposed to pizza," says Pamela Dalton of the Monell Chemical Senses Center in Philadelphia, who studies how we perceive good smells and bad. When the coffee "odorants" connect with their nerve cells, she says, your brain knows that you've just enjoyed your morning brew. © 2021 npr

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27807 - Posted: 05.08.2021

By Christina Caron When Laura Drager contracted Covid-19 in July, it was as though someone had suddenly muted her olfactory system. One morning she was sipping her favorite Gatorade (the yellow one), and two hours later the drink was completely flavorless. She immediately lit a candle and blew it out, but she couldn’t smell the smoke. Her sense of smell had disappeared. Now, she said, “everything either tastes like bleach or tastes like nothing.” Over the past few months she has lost 19 pounds. “I don’t have that ‘I’m hungry’ feeling,” said Ms. Drager, 41, who lives in Sevierville, Tenn., about 45 minutes from Knoxville. “I think you forget how much smell and taste is a part of your life until it goes away.” As the coronavirus continues to spread, there are increasing numbers of people who have either lost their senses of smell after contracting Covid or are struggling with parosmia, a disturbing disorder that causes previously normal odors to develop a new, often unpleasant aroma. One meta-analysis published in September found that as many as 77 percent of those who had Covid were estimated to have some form of smell loss as a result of their infections. The recommended treatment for these conditions is smell training. But how exactly do you do it, and why should you bother? © 2021 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27745 - Posted: 03.27.2021

By Alyson Krueger Samantha LaLiberte, a social worker in Nashville, thought she had made a full recovery from Covid-19. But in mid-November, about seven months after she’d been sick, a takeout order smelled so foul that she threw it away. When she stopped by the house of a friend who was cooking, she ran outside and vomited on the front lawn. “I stopped going places, even to my mom’s house or to dinner with friends, because anything from food to candles smelled so terrible,” Ms. LaLiberte, 35, said. “My relationships are strained.” She is dealing with parosmia, a distortion of smell such that previously enjoyable aromas — like that of fresh coffee or a romantic partner — may become unpleasant and even intolerable. Along with anosmia, or diminished sense of smell, it is a symptom that has lingered with some people who have recovered from Covid-19. The exact number of people experiencing parosmia is unknown. One recent review found that 47 percent of people with Covid-19 had smell and taste changes; of those, about half reported developing parosmia. “That means that a rose might smell like feces,” said Dr. Richard Doty, director of the Smell and Taste Center at the University of Pennsylvania. He noted that people typically recover their smell within months. Right now, Ms. LaLiberte can’t stand the scent of her own body. Showering is no help; the smell of her body wash, conditioner and shampoo made her sick. What’s more, she detected the same odor on her husband of eight years. “There is not a whole lot of intimacy right now,” she said. “And it’s not because we don’t want to.” “It’s a much bigger issue than people give it credit for,” said Dr. Duika Burges Watson, who leads the Altered Eating Research Network at Newcastle University in England and submitted a journal research paper on the topic. “It is something affecting your relationship with yourself, with others, your social life, your intimate relationships.” © 2021 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 8: Hormones and Sex
Link ID: 27742 - Posted: 03.23.2021

By William Weir There are a few ways we perceive food, and not all are particularly well-understood. We know that much of it happens in the olfactory bulb, a small lump of tissue between the eyes and behind the nose, but how the stimuli arrive at this part of the brain is still being worked out. How these stimuli are processed in the brain plays a major role in our daily life. Fully understanding how our perceptions of food are formed is critical, Fahmeed Hyder said, but getting a clear picture of what our brains do when we smell has been tricky. “Knowing which exact pathways are affected and teaching our brain to appreciate and acknowledge both modes of perception in understanding the flavor is a part of our culture that we haven’t fully exploited yet,” he said. A better understanding of how smells get to our brain would not only tell us a lot about our eating habits, he said, it could even potentially help patients of certain diseases. Hyder, professor of biomedical engineering and radiology & biomedical imaging, has taken a detailed look at the function of the olfactory bulb. It may not be one of the most talked-about regions of the brain, but it helps us make sense of the outside world by taking in molecules from food — known as food volatiles — and then sending these signals further into the brain. It serves a pivotal role as the gateway for chemical stimuli to the rest of the brain — specifically the piriform cortex, amygdala, and hippocampus. To see exactly how it does that, Hyder and his team mapped the activity in the entire olfactory bulb. It’s the first time that this has ever been done for the two independent routes of odor delivery — that is, the orthonasal and retronasal routes. The results were published in NeuroImage. Copyright © 2021 Yale University

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27691 - Posted: 02.15.2021

By Brooke Jarvis Danielle Reed stopped counting after the 156th email arrived in a single afternoon. It was late March, and her laboratory at the Monell Chemical Senses Center in Philadelphia had abruptly gone into Covid-19 lockdown. For weeks, there had been little to do. Reed, who is famous in her field for helping to discover a new family of receptors that perceive bitter flavors, had spent years studying the way human genetics affect the way we experience smell and taste. It was important but niche science that seemingly had little to do with a dangerous respiratory virus spreading around the globe. And then one Saturday, she checked her email. Reed watched in amazement as the messages proliferated. It wasn’t how many threads there were, though that was overwhelming, but the way they seemed to grow like Hydras, sprouting in all directions. Recipients copied other people they thought might be interested in the discussion, who added more people, who added still others, across a huge range of countries and disciplines. The cascading emails were all responding to the same rather obscure news alert, meant for ear, nose and throat doctors based in Britain. It was titled: “Loss of smell as marker of Covid-19 infection.” The week before, Claire Hopkins, the president of the British Rhinological Society and an author of the alert, was seeing patients in her clinic in London when she noticed something odd. Hopkins, who specializes in nose and sinus diseases, especially nasal polyps, was accustomed to seeing the occasional patient — usually about one per month — whose sense of smell disappeared after a viral infection. Most of the time, such losses were fairly self-explanatory: A stuffy, inflamed nose keeps odorants from reaching the smell receptors at the top of the airway. Sometimes these receptors are also damaged by inflammation and need time to recover. But patients were now arriving with no blockage or swelling, no trouble breathing, no notable symptoms, other than the sudden and mysterious disappearance of their ability to smell. And there were nine of them. © 2021 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27672 - Posted: 01.30.2021

Katherine J. Wu In a perfect world, the entrance to every office, restaurant and school would offer a coronavirus test — one with absolute accuracy, and able to instantly determine who was virus-free and safe to admit and who, positively infected, should be turned away. That reality does not exist. But as the nation struggles to regain a semblance of normal life amid the uncontrolled spread of the virus, some scientists think that a quick test consisting of little more than a stinky strip of paper might at least get us close. The test does not look for the virus itself, nor can it diagnose disease. Rather, it screens for one of Covid-19’s trademark signs: the loss of the sense of smell. Since last spring, many researchers have come to recognize the symptom, which is also known as anosmia, as one of the best indicators of an ongoing coronavirus infection, capable of identifying even people who don’t otherwise feel sick. A smell test cannot flag people who contract the coronavirus and never develop any symptoms at all. But in a study that has not yet been published in a scientific journal, a mathematical model showed that sniff-based tests, if administered sufficiently widely and frequently, might detect enough cases to substantially drive transmission down. Daniel Larremore, an epidemiologist at the University of Colorado, Boulder, and the study’s lead author, stressed that his team’s work was still purely theoretical. Although some smell tests are already in use in clinical and research settings, the products tend to be expensive and laborious to use and are not widely available. And in the context of the pandemic, there is not yet real-world data to support the effectiveness of smell tests as a frequent screen for the coronavirus. Given the many testing woes that have stymied pandemic control efforts so far, some experts have been doubtful that smell tests could be distributed widely enough, or made sufficiently cheat-proof, to reduce the spread of infection. © 2021 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27656 - Posted: 01.20.2021

Michael Marshall One treatment for survivors of COVID-19 who have lost their sense of smell is 'smell training', in which they relearn prescribed scents, such as those of roses and lemons.Credit: Christine E. Kelly Early in the COVID-19 pandemic, it emerged that many people infected with the SARS-CoV-2 virus were losing their sense of smell — even without displaying other symptoms. Researchers also discovered that infected people could lose their sense of taste and their ability to detect chemically triggered sensations such as spiciness, called chemesthesis. Almost a year later, some still haven’t recovered these senses, and for a proportion of people who have, odours are now warped: unpleasant scents have taken the place of normally delightful ones. Nature surveys the science behind this potentially long-lasting and debilitating phenomenon. How many people with COVID-19 lose their sense of smell? The exact percentage varies between studies, but most suggest that smell loss is a common symptom. One review published last June1 compiled data from 8,438 people with COVID-19, and found that 41% had reported experiencing smell loss. In another study, published in August2, a team led by researcher Shima T. Moein at the Institute for Research in Fundamental Sciences in Tehran, Iran, administered a smell-identification test to 100 people with COVID-19 in which the subjects sniffed odours and identified them on a multiple-choice basis. Ninety-six per cent of the participants had some olfactory dysfunction, and 18% had total smell loss (otherwise known as anosmia). © 2021 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27649 - Posted: 01.15.2021