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

By Roni Caryn Rabin Until March, when everything started tasting like cardboard, Katherine Hansen had such a keen sense of smell that she could recreate almost any restaurant dish at home without the recipe, just by recalling the scents and flavors. Then the coronavirus arrived. One of Ms. Hansen’s first symptoms was a loss of smell, and then of taste. Ms. Hansen still cannot taste food, and says she can’t even tolerate chewing it. Now she lives mostly on soups and shakes. “I’m like someone who loses their eyesight as an adult,” said Ms. Hansen, a realtor who lives outside Seattle. “They know what something should look like. I know what it should taste like, but I can’t get there.” A diminished sense of smell, called anosmia, has emerged as one of the telltale symptoms of Covid-19, the illness caused by the coronavirus. It is the first symptom for some patients, and sometimes the only one. Often accompanied by an inability to taste, anosmia occurs abruptly and dramatically in these patients, almost as if a switch had been flipped. Most regain their senses of smell and taste after they recover, usually within weeks. But in a minority of patients like Ms. Hansen, the loss persists, and doctors cannot say when or if the senses will return. Scientists know little about how the virus causes persistent anosmia or how to cure it. But cases are piling up as the coronavirus sweeps across the world, and some experts fear that the pandemic may leave huge numbers of people with a permanent loss of smell and taste. The prospect has set off an urgent scramble among researchers to learn more about why patients are losing these essential senses, and how to help them. “Many people have been doing olfactory research for decades and getting little attention,” said Dr. Dolores Malaspina, professor of psychiatry, neuroscience, genetics and genomics at Icahn School of Medicine at Mount Sinai in New York. “Covid is just turning that field upside down.” © 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: 27642 - Posted: 01.09.2021

Sam Wollaston A single-storey building in a lonely rural business park, a few miles from Milton Keynes on a grey autumn day. It looks like a location for a bleak thriller: where a kidnap victim is held, perhaps, or the scene of a final shootout. Inside, though, something kind of cool is happening. In a brightly lit room, four inverted metal cups have been placed on the red carpet, each containing a small glass jar. One of these contains a smell: a “training odour”. Into the room bursts Billy, followed by Jess. Billy is a labrador, and Jess his human trainer. Billy bounces about the place, clearly super excited. He sniffs at everything – furniture, people, the cups – wagging ferociously. When he sniffs at the cup that contains the smell, another trainer, Jayde, indicates success with a clicking noise. Billy is rewarded with his favourite toy, a well-chewed rubber ball, and a chorus of “good boy”. So far, so unremarkable. Dogs have excellent noses, everyone knows that. They are estimated to be at least 10,000 times better than ours. It’s not immediately clear just how good Billy is. Did he really find the smell, or did Jayde just click when he sniffed the right cup? To be fair to Billy, he’s young, 18 months old, and this is only his second session. The trainers – Jess, Jayde and Mark – have high hopes for him. And after a couple more goes, it becomes clear that he is definitely finding the right cup, quickly. He is also clearly enjoying the game. What Billy lacks in refinement, he makes up for in youthful enthusiasm and exuberance, and he learns fast. Which is good news: this is just the first stage for Billy, who is on a fast-track training course to learn to sniff out Covid-19. He’s not working with the actual virus, of course, but a training sample, which will teach him to do that job. © 2020 Guardian News & Media 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: 27622 - Posted: 12.12.2020

By Jason Castro To be an expectant mother, or the anxious partner of one, is to be keenly, even agonizingly aware of how chemicals affect a developing life. The basic advice is well known, and obsessively followed: Alcohol in strict moderation, and no nicotine at all. Don’t mess with mercury. Folic acid is your friend. More protein and less caffeine. Stay away from BPA, PBCs and PFA, and generally make an enemy of the unpronounceable. But, if we take the results of a provocative recent paper seriously, there may be another important, and deeply underappreciated chemical influence at work: a man’s odor. The research, by a team headed by Noam Sobel of the Weizmann Institute of Science, suggests that there is a relationship between women’s response to “social odors” contained in male sweat and the heartbreaking condition of unexplained repeated pregnancy loss (uRPL). Specifically, in blind smell-tests, these scientists observed that women who had experienced uRPL were significantly better at identifying their spouse’s odor than age-matched controls. Additionally, their brains responded differently to nonspouse odors and they displayed unique olfactory neuroanatomy. Taken in the context of a large body of literature on chemosignaling in nonhuman animals, these results make it conceivable that the human nose could also communicate with the womb and may even influence a pregnancy. So far, the results are strictly correlative, and in no way point to male odor as some kind of pheromonal smoking gun that explains pregnancy loss. Hypothetically, it could also be true that women experiencing uRPL have, on average, larger middle toes, larger whites of their eyes, thinner wrists and a proclivity for wearing purple socks. None of these would give one pause or prompt a serious search for some kind of causal link to pregnancy loss. Yet this particular link between smell and pregnancy loss is intriguing because of how prevalent and robust it is in other mammals, including primates. Many miscarriages still have unexplained causes, which makes any lead, correlative or not, a particularly interesting and worthwhile area of research. © 2020 Scientific American

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: 27619 - Posted: 12.09.2020

David Cox Seven years ago, rhinology surgeon Peter Andrews found himself performing an operation that would go on to change the course of his career. Andrews was operating on a patient who had broken his nose many decades earlier after being struck by a cricket ball. The procedure was delicate: straightening the septum – the thin wall of cartilage that separates the nostrils – and in the process improving his breathing, which had become more laboured in later life. But it had a surprising outcome. As well being able to breathe more freely, Andrews’s patient found he could smell again for the first time in 40 years, a remarkable turn of events that provided the medical community with a new insight into our sense of smell, and its capacity to regenerate. Being able to smell is actually a result of a complex neurological process. Smell-specific nerve cells known as olfactory neurons, located high in the nasal cavity, detect molecules in the air such as those released by a perfume, or smoke particles from something burning. They then convey this information via a long nerve fibre running up through the skull, to a part of the brain that makes sense of it all. This network is one of the most adaptable in the entire central nervous system. To keep functioning, it completely regenerates every six weeks, shedding existing olfactory neurons, and creating new ones from scratch. “That’s quite a feat in itself, because those neurons then have to reconnect up into the brain tissue,” says Andrews. But sometimes things can happen that impair its ability to regenerate. An estimated 5% of the general population is believed to have anosmia, the medical term for temporary or permanent smell loss. Anosmia can occur as part of the ageing process, but also in those of all ages due to factors ranging from broken noses to viral infections. © 2020 Guardian News & Media 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: 27618 - Posted: 12.09.2020

Terry Gross Food science writer Harold McGee was in the middle of writing Nose Dive, his book about the science of smell, when he woke up one morning and realized that he couldn't smell his own coffee. Loss of smell has since become associated with COVID-19. In McGee's case, it was the byproduct of a sinus infection. McGee remembers feeling panicked. "I have friends in the kind of clinical side of taste and smell research. And so I immediately contacted them to find out what I could do and why this had happened," he says. "And they basically said, 'You're going to have to wait and see.' " Over the course of a few months, McGee's sense of smell gradually returned. But he still remembers what it was like to live in an odorless world. "It's the kind of thing where you don't notice something until it's gone," he says. "I spent less and less time cooking. There was no point in going out to restaurants because I wasn't really going to enjoy it." McGee's new book is about how smell is essential to our sense of taste, why things smell the way they do and the ways different chemicals combine to create surprising (and sometimes distasteful) odors. "One of the great pleasures of delving into smells in general was discovering over and over again that things that we enjoy in foods are actually found elsewhere in the world," he says. "And in as unlikely places as cat pee and human sweat, for example." © 2020 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: 27583 - Posted: 11.16.2020

By Jonathan Lambert Octopus arms have minds of their own. Each of these eight supple yet powerful limbs can explore the seafloor in search of prey, snatching crabs from hiding spots without direction from the octopus’ brain. But how each arm can tell what it’s grasping has remained a mystery. Now, researchers have identified specialized cells not seen in other animals that allow octopuses to “taste” with their arms. Embedded in the suckers, these cells enable the arms to do double duty of touch and taste by detecting chemicals produced by many aquatic creatures. This may help an arm quickly distinguish food from rocks or poisonous prey, Harvard University molecular biologist Nicholas Bellono and his colleagues report online October 29 in Cell. The findings provide another clue about the unique evolutionary path octopuses have taken toward intelligence. Instead of being concentrated in the brain, two-thirds of the nerve cells in an octopus are distributed among the arms, allowing the flexible appendages to operate semi-independently (SN: 4/16/15). “There was a huge gap in knowledge of how octopus [arms] actually collect information about their environment,” says Tamar Gutnick, a neurobiologist who studies octopuses at Hebrew University of Jerusalem who was not involved in the study. “We’ve known that [octopuses] taste by touch, but knowing it and understanding how it’s actually working is a very different thing.” Working out the specifics of how arms sense and process information is crucial for understanding octopus intelligence, she says. “It’s really exciting to see someone taking a comprehensive look at the cell types involved,” and how they work. © Society for Science & the Public 2000–2020

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: 27560 - Posted: 10.31.2020

By Katherine J. Wu Researchers in Iceland have identified a new mutant superpower — but the genetic trait probably won’t be granting anyone admission to the X-Men. A small contingent of the world’s population carries a mutation that makes them immune to the odious funk that wafts off fish, according to a study of some 11,000 people published Thursday in the journal Current Biology. The trait is rare, but potent: When faced with a synthetic odor that would put many people off their lunch, some test subjects smelled only the pleasant aroma of caramel, potato or rose. The vast majority of people aren’t so lucky. Nearly 98 percent of Icelanders, the research said, are probably as put off by the scent as you’d expect. The mutation is thought to be even rarer in populations in other countries. “I can assure you I do not have this mutation,” said Dr. Kári Stefánsson, a neurologist and the study’s senior author. “I tend to get nauseated when I get close to fish that is not completely fresh.” Dr. Stefánsson is the founder and chief executive of deCODE genetics, a biopharmaceutical company in Iceland’s capital, Reykjavik, which has been parsing the human genome for several decades. The team’s latest caper involved a deep dive into the underappreciated sense of olfaction. Study participants were asked to take a whiff of six Sniffin’ Sticks — pens imbued with synthetic odors resembling the recognizable scents of cinnamon, peppermint, banana, licorice, lemon and fish. They were asked to identify the smell, then rate its intensity and pleasantness. The older the study subjects were, the more they struggled to accurately pinpoint the scents. That’s unsurprising, given that sensory functions tend to decline later in life, said Rósa Gísladóttir, the study’s lead author. But even younger people didn’t always hit the mark, she said. The lemon and banana sticks, for instance, prompted descriptions of gummy bears and other candy-sweet smells. © 2020 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: 27519 - Posted: 10.10.2020