Chapter 6. Hearing, Balance, Taste, and Smell

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By Amber Dance We’ve all heard of the five tastes our tongues can detect — sweet, sour, bitter, savory-umami and salty. But the real number is actually six, because we have two separate salt-taste systems. One of them detects the attractive, relatively low levels of salt that make potato chips taste delicious. The other one registers high levels of salt — enough to make overly salted food offensive and deter overconsumption. Exactly how our taste buds sense the two kinds of saltiness is a mystery that’s taken some 40 years of scientific inquiry to unravel, and researchers haven’t solved all the details yet. In fact, the more they look at salt sensation, the weirder it gets. Many other details of taste have been worked out over the past 25 years. For sweet, bitter and umami, it’s known that molecular receptors on certain taste bud cells recognize the food molecules and, when activated, kick off a series of events that ultimately sends signals to the brain. Sour is slightly different: It is detected by taste bud cells that respond to acidity, researchers recently learned. In the case of salt, scientists understand many details about the low-salt receptor, but a complete description of the high-salt receptor has lagged, as has an understanding of which taste bud cells host each detector. “There are a lot of gaps still in our knowledge — especially salt taste. I would call it one of the biggest gaps,” says Maik Behrens, a taste researcher at the Leibniz Institute for Food Systems Biology in Freising, Germany. “There are always missing pieces in the puzzle.” A fine balance Our dual perception of saltiness helps us to walk a tightrope between the two faces of sodium, an element that’s crucial for the function of muscles and nerves but dangerous in high quantities. To tightly control salt levels, the body manages the amount of sodium it lets out in urine, and controls how much comes in through the mouth. © 2023 Annual Reviews

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28908 - Posted: 09.16.2023

By David Grimm Apart from Garfield’s legendary love of lasagna, perhaps no food is more associated with cats than tuna. The dish is a staple of everything from The New Yorker cartoons to Meow Mix jingles—and more than 6% of all wild-caught fish goes into cat food. Yet tuna (or any seafood for that matter) is an odd favorite for an animal that evolved in the desert. Now, researchers say they have found a biological explanation for this curious craving. In a study published this month in Chemical Senses, scientists report that cat taste buds contain the receptors needed to detect umami—the savory, deep flavor of various meats, and one of the five basic tastes in addition to sweet, sour, salty, and bitter. Indeed, umami appears to be the primary flavor cats seek out. That’s no surprise for an obligate carnivore. But the team also found these cat receptors are uniquely tuned to molecules found at high concentrations in tuna, revealing why our feline friends seem to prefer this delicacy over all others. “This is an important study that will help us better understand the preferences of our familiar pets,” says Yasuka Toda, a molecular biologist at Meiji University and a leader in studying the evolution of umami taste in mammals and birds. The work could help pet food companies develop healthier diets and more palatable medications for cats, says Toda, who was not involved with the industry-funded study. Cats have a unique palate. They can’t taste sugar because they lack a key protein for sensing it. That’s probably because there’s no sugar in meat, says Scott McGrane, a flavor scientist and research manager for the sensory science team at the Waltham Petcare Science Institute, which is owned by pet food–maker Mars Petcare UK. There’s a saying in evolution, he says: “If you don’t use it, you lose it.” Cats also have fewer bitter taste receptors than humans do—a common trait in uber-carnivores. But cats must taste something, McGrane reasoned, and that something is likely the savory flavor of meat. In humans and many other animals, two genes—Tas1r1 and Tas1r3—encode proteins that join together in taste buds to form a receptor that detects umami. Previous work had shown that cats express the Tas1r3 gene in their taste buds, but it was unclear whether they had the other critical puzzle piece.

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 28885 - Posted: 08.26.2023

By Claudia López Lloreda In what seems like something out of a sci-fi movie, scientists have plucked the famous Pink Floyd song “Another Brick in the Wall” from individuals’ brains. Using electrodes, computer models and brain scans, researchers previously have been able to decode and reconstruct individual words and entire thoughts from people’s brain activity (SN: 11/15/22; SN: 5/1/23). The new study, published August 15 in PLOS Biology, adds music into the mix, showing that songs can also be decoded from brain activity and revealing how different brain areas pick up an array of acoustical elements. The finding could eventually help improve devices that allow communication from people with paralysis or other conditions that limit one’s ability to speak. People listened to Pink Floyd’s “Another Brick in the Wall” song while having their brain activity monitored. Using that data and a computer model, researchers were able to reconstruct sounds that resemble the song. To decode the song, neuroscientist Ludovic Bellier of the University of California, Berkeley and colleagues analyzed the brain activity recorded by electrodes implanted in the brains of 29 individuals with epilepsy. While in the hospital undergoing monitoring for the disorder, the individuals listened to the 1979 rock song. People’s nerve cells, particularly those in auditory areas, responded to hearing the song, and the electrodes detected not only neural signals associated with words but also rhythm, harmony and other musical aspects, the team found. With that information, the researchers developed a computer model to reconstruct sounds from the brain activity data, and found that they could produce sounds that resemble the song. © Society for Science & the Public 2000–2023.

Keyword: Hearing; Brain imaging
Link ID: 28876 - Posted: 08.19.2023

By Elizabeth Preston Some things need no translation. No matter what language you speak, you can probably recognize a fellow human who is cheering in triumph or swearing in anger. If you are a crocodile, you may recognize the sound of a young animal crying in distress, even if that animal is a totally different species — like, say, a human baby. That sound means you are close to a meal. In a study published Wednesday in Proceedings of the Royal Society B, researchers put speakers near crocodiles and played recordings of human, bonobo and chimpanzee infants. The crocodiles were attracted to the cries, especially shrieks that sounded more distressed. “That means that distress is something that is shared by species that are really, really distant,” said Nicolas Grimault, a bioacoustic research director at the French National Centre for Scientific Research and one of the paper’s authors. “You have some kind of emotional communication between crocodiles and humans.” These infant wails most likely drew crocodiles because they signaled an easy meal nearby, the authors say. But in some cases, the opposite may have been true: The crocs were trying to help. The animals in the study were Nile crocodiles, African predators that can reach up to 18 feet long. Understandably, the researchers kept their distance. They visited the reptiles at a Moroccan zoo and placed remote-controlled loudspeakers on the banks of outdoor ponds. The researchers played recordings of cries from those speakers while groups of up to 25 crocodiles were nearby. Some cries came from infant chimpanzees or bonobos calling to their mothers. Others were human babies, recorded either at bath time or in the doctor’s office during a vaccination. Nearly all of the recordings prompted some crocodiles to look or to move toward the speaker. When they heard the sounds of human babies getting shots, for example, almost half the crocodiles in a group responded. Dr. Grimault said the reptiles seemed most tempted by cries with a harsh quality that other studies have linked to distress in mammals. © 2023 The New York Times Company

Keyword: Hearing; Evolution
Link ID: 28871 - Posted: 08.09.2023

By Aara'L Yarber When the pandemic began, losing your sense of smell was considered a key indicator of covid-19, and the condition affected about half of those who tested positive for the coronavirus. However, a new study reveals that the chance of smell loss from the latest omicron variants has dropped dramatically since the early days of the pandemic. “So now, three people out of 100 getting covid presumably may lose their sense of smell, which is far, far less than it was before,” said study leader Evan Reiter, the medical director of Virginia Commonwealth University Health’s Smell and Taste Disorders Center. The findings, published in the journal Otolaryngology — Head and Neck Surgery, mean that losing smell and, by association, your sense of taste is no longer a reliable sign that someone has a covid infection, Reiter said. Advertisement “Now, the chance of you having [smell loss from] covid as opposed to another virus, like different cold and flu bugs, is about the same,” he said. Although it is unclear why the frequency of smell loss has decreased over time, vaccinations and preexisting immunity could be playing a role, the researchers said. Doctors have had difficulty explaining the cause of smell loss, but some research suggests it is due to covid triggering a prolonged immune assault on olfactory nerve cells. These cells sit at the top of the nasal cavity and help send smell signals from the nose to the brain. It is possible that over time this attack causes a decline in the number of olfactory cells. But if you’ve already been infected or vaccinated, the time the virus has to inflict this kind of damage is dramatically reduced, said Benjamin tenOever, a professor of microbiology and medicine at New York University who was not involved in the study.

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28866 - Posted: 08.05.2023

By Tanvi Dutta Gupta The Arctic Ocean is a noisy place. Creatures of the deep have learned to live with the cacophony of creaking ice sheets and breaking icebergs, but humanmade sources of noise from ships and oil and gas infrastructure are altering that natural submarine soundscape. Now, a research team has found that even subtle underwater noise pollution can cause narwhals to make shallower dives and cut their hunts short. The research, published today in Science Advances, uncovers “some really great information on a species we know very little about,” says Ari Friedlaender, an ocean ecologist at the University of California, Santa Cruz, not involved in the study. Knowing how the whales react to these noises could help conservationists “act proactively” to protect the animals in their Arctic home where warming waters already threaten their lifestyles. Narwhals—with their long, unicornlike horns extending from their faces—live in one of the most extreme environments in the world, explains Outi Tervo, an ecologist at the Greenland Institute of Natural Resources and the study’s first author. Each narwhal returns in summer to the same small fjord where it was born in order to feed on fish, squid, and shrimp. As humans increasingly encroach on Arctic waters, though, scientists, conservationists, and Inuit communities have worried about how development and ship traffic will affect the whales. Many of Greenland’s Inuit communities rely on the narwhals as a culturally important food source. When Greenland’s government started to auction new permits for offshore oil exploration in 2011, Tervo and colleagues decided to examine whether the noise pollution associated with such development affected narwhals. For instance, boats exploring the sea floor tow instruments called airguns, which blast air a few meters below the vessels to sonically suss out the presence of cavities that may contain oil and gas. Those pulses can be the “loudest sound put in the ocean by humans,” says study co-author Susanna Blackwell, a biologist with Greeneridge Sciences.

Keyword: Animal Communication; Hearing
Link ID: 28858 - Posted: 07.27.2023

By Freda Kreier Pregnancy can do weird things to the body. For some bats, it can hamper their ability to “see” the world around them. Kuhl’s pipistrelle bats (Pipistrellus kuhlii) echolocate less frequently while pregnant, researchers report March 28 in BMC Biology. The change may make it harder for the tiny bats to detect prey and potential obstacles in the environment. The study is among the first to show that pregnancy can shape how nonhuman mammals sense their surroundings, says Yossi Yovel, a neuroecologist at Tel Aviv University in Israel. Nocturnal bats like Kuhl’s pipistrelles famously use sound to navigate and hunt prey in the dark (SN: 9/20/17). Their calls bounce off whatever is nearby and bats use the echoes to reconstruct what’s around them, a process aptly named echolocation. The faster a bat makes calls, the better it can make out its surroundings. But rapid-fire calling requires breathing deeply, which is something that pregnancy can get in the way of. “Although I’ve never been pregnant, I know that when I eat a lot, it’s more difficult to breathe,” Yovel says. So pregnancy — which can add a full gram to a 7-gram Kuhl’s pipistrelle and may push up on the lungs — might hamper echolocation. Yovel and colleagues tested their hypothesis by capturing 10 Kuhl’s pipistrelles, five of whom were pregnant, and training the bats to find and land on a platform. Recordings of the animals’ calls revealed that bats that weren’t pregnant made around 130 calls on average while searching for the platform. But bats that were pregnant made only around 110 calls, or 15 percent fewer. © Society for Science & the Public 2000–2023.

Keyword: Hearing; Hormones & Behavior
Link ID: 28774 - Posted: 05.10.2023

By Neelam Bohra Ayla Wing’s middle school students don’t always know what to make of their 26-year-old teacher’s hearing aids. The most common response she hears: “Oh, my grandma has them, too.” But grandma’s hearing aids were never like this: Bluetooth-enabled and connected to her phone, they allow Ms. Wing to toggle with one touch between custom settings. She can shut out the world during a screeching subway ride, hear her friends in noisy bars during a night out and even understand her students better by switching to “mumbly kids.” A raft of new hearing aids have hit the market in recent years, offering greater appeal to a generation of young adults that some experts say is both developing hearing problems earlier in life and — perhaps paradoxically — becoming more comfortable with an expensive piece of technology pumping sound into their ears. Some of the new models, including Ms. Wing’s, are made by traditional prescription brands, which usually require a visit to a specialist. But the Food and Drug Administration opened up the market last year when it allowed the sale of hearing aids over the counter. In response, brand names like Sony and Jabra began releasing their own products, adding to the new wave of designs and features that appeal to young consumers. “These new hearing aids are sexy,” said Pete Bilzerian, a 25-year-old in Richmond, Va., who has worn the devices since he was 7. He describes his early models as distinctly unsexy: “big, funky, tan-colored hearing aids with the molding that goes all around the ear.” But increasingly, those have given way to sleeker, smaller models with more technological capabilities. Nowadays, he said, no one seems to notice the electronics in his ear. “If it ever does come up as a topic, I just brush it off and say, ‘Hey, I got these very expensive AirPods.’” More people in Mr. Bilzerian’s age group might need the equivalent of expensive AirPods, experts say. By the time they turn 30, about a fifth of Americans today have had their hearing damaged by noise, the Centers for Disease Control and Prevention recently estimated. This number adds to the already substantial population of young people with hearing loss tied to genetics or medical conditions. © 2023 The New York Times Company

Keyword: Hearing
Link ID: 28770 - Posted: 05.06.2023

By Wynne Parry For the first time, researchers have determined how a human olfactory receptor captures an airborne scent molecule, the pivotal chemical event that triggers our sense of smell. Whether it evokes roses or vanilla, cigarettes or gasoline, every scent starts with free-floating odor molecules that latch onto receptors in the nose. Multitudes of such unions produce the perception of the smells we love, loathe or tolerate. Researchers therefore want to know in granular detail how smell sensors detect and respond to odor molecules. Yet human smell receptors have resisted attempts to visualize how they work in detail — until now. In a recent paper published in Nature, a team of researchers delineated the elusive three-dimensional structure of one of these receptors in the act of holding its quarry, a compound that contributes to the aroma of Swiss cheese and body odor. “People have been puzzled about the actual structure of olfactory receptors for decades,” said Michael Schmuker, who uses chemical informatics to study olfaction at the University of Hertfordshire in England. Schmuker was not involved in the study, which he describes as “a real breakthrough.” He and others who study our sense of smell say that the reported structure represents a step toward better understanding how the nose and brain jointly wring from airborne chemicals the sensations that warn of rotten food, evoke childhood memories, help us find mates and serve other crucial functions. The complexity of the chemistry that the nose detects has made olfaction particularly difficult to explain. Researchers think that human noses possess about 400 types of olfactory receptors, which are tasked with detecting a vastly larger number of odoriferous “volatiles,” molecules that vaporize readily, from the three-atom, rotten-egg-smelling hydrogen sulfide to the much larger, musky-scented muscone. (One recent estimate put the number of possible odor-bearing compounds at 40 billion or more.) == All Rights Reserved © 2023

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28766 - Posted: 05.03.2023

Sara Reardon Octopuses and squids both use the suckers on their limbs to grapple with their prey and to taste their quarry at the same time. Now, a pair of studies describes how these animals ‘taste by touching’ — and how evolution has equipped them with the perfect sensory ability for their lifestyles1,2. The papers were published in Nature on 12 April. The research details the structure of the receptors that stud the animals’ suckers. These receptors transmit information that enables the creature to taste chemicals on a surface independently from those floating in the water. Armed with brains Cephalopods — the group that includes octopuses and squids — have long fascinated neuroscientists because their brains and sensory systems are unlike those found in any other animals. Octopuses, for instance, have more neurons in their arms than in their central brain: a structure that allows each arm to function independently as if it has its own brain3. And researchers have long known that the hundreds of suckers on each arm can both feel the environment and taste it4. Molecular biologist Nicholas Bellono at Harvard University in Cambridge, Massachusetts, and his group were studying the California two-spot octopus (Octopus bimaculoides) when they came across a distinctive structure on the surface of the animal’s tentacle cells. Bellono suspected that this structure acted as a receptor for chemicals in the octopus’s environment. He contacted neurobiologist Ryan Hibbs at the University of California San Diego, who studies receptors that are architecturally similar to the octopus structures found by Bellono’s team: both types consist of five barrel-like proteins clustered to form a hollow tube. When the researchers looked at the octopus genome, they found 26 genes for these barrel-shaped proteins, which could be shuffled to create millions of distinct five-part combinations that detect various tastes1. The researchers found that the octopus receptors tend to bind to ‘greasy’ molecules that don’t dissolve in water, suggesting that they are optimized for detecting chemicals on surfaces such as a fish’s skin, the sea floor or the octopus’s own eggs. © 2023 Springer Nature Limited

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28741 - Posted: 04.15.2023

Nicola Davis Science Correspondent If the sound of someone chewing gum or slurping their tea gets on your nerves, you are not alone. Researchers say almost one in five people in the UK has strong negative reactions to such noises. Misophonia is a disorder in which people feel strong emotional responses to certain sounds, feeling angry, distressed or even unable to function in social or work settings as a result. But just how common the condition is has been a matter of debate. Now researchers say they have found 18.4% of the UK population have significant symptoms of misophonia. “This is the very first study where we have a representative sample of the UK population,” said Dr Silia Vitoratou, first author of the study at King’s College London. “Most people with misophonia think they are alone, but they are not. This is something we need to know [about] and make adjustments if we can.” Writing in the journal Plos One, the team report how they gathered responses from 768 people using metrics including the selective sound sensitivity syndrome scale. This included one questionnaire probing the sounds that individuals found triggering, such as chewing or snoring, and another exploring the impact of such sounds – including whether they affected participants’ social life and whether the participant blamed the noise-maker – as well as the type of emotional response participants felt to the sounds and the intensity of their emotions. As a result, each participant was given an overall score. The results reveal more than 80% of participants had no particular feelings towards sounds such as “normal breathing” or “yawning” but this plummeted to less than 25% when it came to sounds including “slurping”, “chewing gum” and “sniffing”. © 2023 Guardian News & Media Limited

Keyword: Hearing; Attention
Link ID: 28712 - Posted: 03.23.2023

Miryam Naddaf It is thanks to proteins in the nose called odour receptors that we find the smell of roses pleasant and that of rotting food foul. But little is known about how these receptors detect molecules and translate them into scents. Now, for the first time, researchers have mapped the precise 3D structure of a human odour receptor, taking a step forwards in understanding the most enigmatic of our senses. The study, published in Nature on 15 March1, describes an olfactory receptor called OR51E2 and shows how it ‘recognizes’ the smell of cheese through specific molecular interactions that switch the receptor on. “It’s basically our first picture of any odour molecule interacting with one of our odour receptors,” says study co-author Aashish Manglik, a pharmaceutical chemist at the University of California, San Francisco. Smell mystery The human genome contains genes encoding 400 olfactory receptors that can detect many odours. Mammalian odour-receptor genes were first discovered in rats by molecular biologist Richard Axel and biologist Linda Buck in 19912. Researchers in the 1920s estimated that the human nose could discern around 10,000 smells3, but a 2014 study suggests that we can distinguish more than one trillion scents4. Each olfactory receptor can interact with only a subset of smelly molecules called odorants — and a single odorant can activate multiple receptors. It is “like hitting a chord on a piano”, says Manglik. “Instead of hitting a single note, it’s a combination of keys that are hit that gives rise to the perception of a distinct odour.” Beyond this, little is known about exactly how olfactory receptors recognize specific odorants and encode different smells in the brain. Technical challenges in producing mammalian olfactory-receptor proteins using standard laboratory methods have made it difficult to study how these receptors bind to odorants. © 2023 Springer Nature Limited

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28710 - Posted: 03.18.2023

By Dana Mackenzie On October 2, 2022, four days after Hurricane Ian hit Florida, a search-and-rescue Rottweiler named Ares was walking the ravaged streets of Fort Myers when the moment came that he had been training for. Ares picked up a scent within a smashed home and raced upstairs, with his handler trailing behind, picking his way gingerly through the debris. They found a man who had been trapped inside his bathroom for two days after the ceiling caved in. Some 152 people died in Ian, one of Florida’s worst hurricanes, but that lucky man survived thanks to Ares’ ability to follow a scent to its source. We often take for granted the ability of a dog to find a person buried under rubble, a moth to follow a scent plume to its mate or a mosquito to smell the carbon dioxide you exhale. Yet navigating by nose is more difficult than it might appear, and scientists are still working out how animals do it. “What makes it hard is that odors, unlike light and sound, don’t travel in a straight line,” says Gautam Reddy, a biological physicist at Harvard University who coauthored a survey of the way animals locate odor sources in the 2022 Annual Review of Condensed Matter Physics. You can see the problem by looking at a plume of cigarette smoke. At first it rises and travels in a more or less straight path, but very soon it starts to oscillate and finally it starts to tumble chaotically, in a process called turbulent flow. How could an animal follow such a convoluted route back to its origin? Over the last couple of decades, a suite of new high-tech tools, ranging from genetic modification to virtual reality to mathematical models, have made it possible to explore olfactory navigation in radically different ways. The strategies that animals use, as well as their success rates, turn out to depend on a variety of factors, including the animal’s body shape, its cognitive abilities and the amount of turbulence in the odor plume. One day, this growing understanding may help scientists develop robots that can accomplish tasks that we now depend on animals for: dogs to search for missing people, pigs to search for truffles and, sometimes, rats to search for land mines. © 2023 Annual Reviews

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28692 - Posted: 03.08.2023

By Veronique Greenwood It is the rare person who likes hearing their own voice on a recording. It sounds fake, somehow — like it belongs to someone else. For neuroscientists, that quality of otherness is more than a curiosity. Many mysteries remain about the origins of hallucinations, but one hypothesis suggests that when people hear voices, they are hearing their own thoughts disguised as another person’s by a quirk of the brain. Scientists would like to understand what parts of the brain allow us to recognize ourselves speaking, but studying this using recordings of people’s own voices has proved tricky. When we talk, we not only hear our voice with our ears, but on some level we feel it as the sound vibrations travel through the bones of the skull. A study published Wednesday in the journal Royal Society Open Science attempted a workaround. A team of researchers investigated whether people could more accurately recognize their voices if they wore bone-conduction headphones, which transmit sound via vibration. They found that sending a recording through the facial bones made it easier for people to tell their voices apart from those of strangers, suggesting that this technology provides a better way to study how we can tell when we are speaking. That is a potentially important step in understanding the origins of hallucinated voices. Recordings of our voices tend to sound higher than we expect, said Pavo Orepic, a postdoctoral researcher at the Swiss Federal Institute of Technology who led the study. The vibration of the skull makes your voice sound deeper to yourself than to a listener. But even adjusting recordings so they sound lower doesn’t recreate the experience of hearing your own voice. As an alternative, the team tried using bone-conduction headphones, which are commercially available and often rest on a listener’s cheekbones just in front of the ear. © 2023 The New York Times Company

Keyword: Schizophrenia; Hearing
Link ID: 28669 - Posted: 02.15.2023

By Erin Garcia de Jesús A female giraffe has a great Valentine’s Day gift for potential mates: urine. Distinctive anatomy helps male giraffes get a taste for whether a female is ready to mate, animal behaviorists Lynette and Benjamin Hart report January 19 in Animals. A pheromone-detecting organ in giraffes has a stronger connection to the mouth than the nose, the researchers found. That’s why males scope out which females to mate with by sticking their tongues in a urine stream. Animals such as male gazelles will lick fresh urine on the ground to track if females are ready to mate. But giraffes’ long necks and heavy heads make bending over to investigate urine on the ground an unstable and vulnerable position, says Lynette Hart, of the University of California, Davis. The researchers observed giraffes (Giraffa giraffa angolensis) in Etosha National Park in Namibia in 1994, 2002 and 2004. Bull giraffes nudged or kicked the female to ask her to pee. If she was a willing participant, she urinated for a few seconds, while the male took a sip. Then the male curled his lip and inhaled with his mouth, a behavior called a flehmen response, to pull the female’s scent into two openings on the roof of the mouth. From the mouth, the scent travels to the vomeronasal organ, or VNO, which detects pheromones. The Harts say they never saw a giraffe investigate urine on the ground. Unlike many other mammals, giraffes have a stronger oral connection — via a duct — to the VNO, than a nasal one, examinations of preserved giraffe specimens showed. One possible explanation for the difference could be that a VNO-nose link helps animals that breed at specific times of the year detect seasonal plants, says Benjamin Hart, a veterinarian also at the University of California, Davis. But giraffes can mate any time of year, so the nasal connection may not matter as much. © Society for Science & the Public 2000–2023.

Keyword: Chemical Senses (Smell & Taste); Sexual Behavior
Link ID: 28664 - Posted: 02.15.2023

By Erin Blakemore Tinnitus — a ringing or whistling sound in the ears — plagues millions worldwide. Though the estimates of those bothered by the condition vary, a new study suggests they may have something in common: exposure to road traffic noise at home. The paper, published in Environmental Health Perspectives, looked to Denmark to find a potential link between road noise and tinnitus levels. The nationwide study included data on 3.5 million Danish residents who were 30 and older between 2000 and 2017. Over that time, 40,692 were diagnosed with tinnitus. When the researchers calculated likely traffic and noise levels at the quietest facade of their residences in that period, they found those living with louder road noise were more likely to be diagnosed with tinnitus than those who lived in quieter areas. People’s risk rose 6 percent with every 10-decibel increase in road traffic noise compared with controls. Levels rose the longer a person had been exposed to higher road traffic noise. Women, people without a previous history of hearing loss, and people with higher education and income were at increased risk. The study did not find an association between railway noise and tinnitus diagnoses. Though the paper shows an association between tinnitus and traffic noise, it does not prove that one causes the other. The researchers say it’s important to learn more about the potential effects of residential noise exposure — and posit that if traffic noise does cause tinnitus, it might do so by disrupting people’s sleep. “We know that traffic noise can make us stressed and affect our sleep. And that tinnitus can get worse when we live under stressful situations and we do not sleep well,” said Jesper Hvass Schmidt, an associate professor at the University of Southern Denmark and the paper’s co-author, in a news release.

Keyword: Hearing
Link ID: 28661 - Posted: 02.11.2023

Niyazi Arslan Cochlear implants are among the most successful neural prostheses on the market. These artificial ears have allowed nearly 1 million people globally with severe to profound hearing loss to either regain access to the sounds around them or experience the sense of hearing for the first time. However, the effectiveness of cochlear implants varies greatly across users because of a range of factors, such as hearing loss duration and age at implantation. Children who receive implants at a younger age may may be able to acquire auditory skills similar to their peers with natural hearing. I am a researcher studying pitch perception with cochlear implants. Understanding the mechanics of this technology and its limitations can help lead to potential new developments and improvements in the future. In fully-functional hearing, sound waves enter the ear canal and are converted into neural impulses as they move through hairlike sensory cells in the cochlea, or inner ear. These neural signals then travel through the auditory nerve behind the cochlea to the central auditory areas of the brain, resulting in a perception of sound. Analysis of the world, from experts People with severe to profound hearing loss often have damaged or missing sensory cells and are unable to convert sound waves into electrical signals. Cochlear implants bypass these hairlike cells by directly stimulating the auditory nerve with electrical pulses. Cochlear implants consist of an external part wrapped behind the ear and an internal part implanted under the skin. © 2010–2023, The Conversation US, Inc.

Keyword: Hearing; Robotics
Link ID: 28639 - Posted: 01.25.2023

By Chris Gorski At first glance, saliva seems like pretty boring stuff, merely a convenient way to moisten our food. But the reality is quite different, as scientists are beginning to understand. The fluid interacts with everything that enters the mouth, and even though it is 99 percent water, it has a profound influence on the flavors — and our enjoyment — of what we eat and drink. “It is a liquid, but it’s not just a liquid,” says oral biologist Guy Carpenter of King’s College London. Scientists have long understood some of saliva’s functions: It protects the teeth, makes speech easier and establishes a welcoming environment for foods to enter the mouth. But researchers are now finding that saliva is also a mediator and a translator, influencing how food moves through the mouth and how it sparks our senses. Emerging evidence suggests that interactions between saliva and food may even help to shape which foods we like to eat. The substance is not very salty, which allows people to taste the saltiness of a potato chip. It’s not very acidic, which is why a spritz of lemon can be so stimulating. The fluid’s water and salivary proteins lubricate each mouthful of food, and its enzymes such as amylase and lipase kickstart the process of digestion. This wetting also dissolves the chemical components of taste, or tastants, into saliva so they can travel to and interact with the taste buds. Through saliva, says Jianshe Chen, a food scientist at Zhejiang Gongshang University in Hangzhou, China, “we detect chemical information of food: the flavor, the taste.” © 2023 Annual Reviews

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28637 - Posted: 01.25.2023

Miryam Naddaf Researchers have made transgenic ants whose antennae glow green under a microscope, revealing how the insects’ brains process alarming smells. The findings identify three unique brain regions that respond to alarm signals. In these areas, called glomeruli, the ants’ nerve endings intersect. The work was posted on the bioRxiv preprint server on 29 December 20221 and has not yet been peer reviewed. “Ants are like little walking chemical factories,” says study co-author Daniel Kronauer, a biologist at the Rockefeller University in New York City. Previous research has focused on identifying the chemicals that ants release or analysing the insects’ behavioural responses to these odours, but “how ants can actually smell the pheromones is really only now becoming a little bit clearer”, says Kronauer. “This is the first time that, in a social insect, a particular glomerulus has been associated very strongly with a particular behaviour,” he adds. Smelly signals Ants are social animals that communicate with each other by releasing scented chemicals called pheromones. The clonal raider ants (Ooceraea biroi) that the researchers studied are blind. “They basically live in a world of smells,” says Kronauer. “So the vast amount of their social behaviour is regulated by these chemical compounds.” When an ant perceives danger, it releases alarm pheromones from a gland in its head to warn its nestmates. Other ants respond to this signal by picking up their larvae and evacuating the nest. “Instead of having dedicated brain areas for face recognition or language processing, ants have a massively expanded olfactory system,” says Kronauer. The researchers created transgenic clonal raider ants by injecting the insects’ eggs with a vector carrying a gene for a green fluorescent protein combined with one that expresses a molecule that indicates calcium activity in the brain. © 2023 Springer Nature Limited

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28632 - Posted: 01.18.2023

By Carolyn Wilke Mammals in the ocean swim through a world of sound. But in recent decades, humans have been cranking up the volume, blasting waters with noise from shipping, oil and gas exploration and military operations. New research suggests that such anthropogenic noise may make it harder for dolphins to communicate and work together. When dolphins cooperated on a task in a noisy environment, the animals were not so different from city dwellers on land trying to be heard over a din of jackhammers and ambulance sirens. They yelled, calling louder and longer, researchers reported Thursday in the journal Current Biology. “Even then, there’s a dramatic increase in how often they fail to coordinate,” said Shane Gero, a whale biologist at Carleton University in Ottawa who wasn’t part of the work. The effect of increasing noise was “remarkably clear.” Scientists worked with a dolphin duo, males named Delta and Reese, at an experimental lagoon at the Dolphin Research Center in the Florida Keys. The pair were trained to swim to different spots in their enclosure and push a button within one second of each other. “They’ve always been the most motivated animals. They were really excited about doing the task,” said Pernille Sørensen, a biologist and Ph.D. candidate at the University of Bristol in England. The dolphins talked to each other using whistles and often whistled right before pressing the button, she said. Ms. Sørensen’s team piped in sounds using underwater speakers. Tags, stuck behind the animals’ blowholes, captured what the dolphins heard and called to each other as well as their movements. Through 200 trials with five different sound environments, the team observed how the dolphins changed their behavior to compensate for loud noise. The cetaceans turned their bodies toward each other and paid greater attention to each other’s location. At times, they nearly doubled the length of their calls and amplified their whistles, in a sense shouting, to be heard above cacophonies of white noise or a recording of a pressure washer. © 2023 The New York Times Company

Keyword: Animal Communication; Hearing
Link ID: 28628 - Posted: 01.14.2023