Chapter 9. Hearing, Balance, Taste, and Smell

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Hannah Devlin Science correspondent Music makes you lose control, Missy Elliott once sang on a hit that is almost impossible to hear without bopping along. Now scientists have discovered that rats also find rhythmic beats irresistible, showing how they instinctively move in time to music. This ability was previously thought to be uniquely human and scientists say the discovery provides insights into the animal mind and the origins of music and dance. “Rats displayed innate – that is, without any training or prior exposure to music – beat synchronisation,” said Dr Hirokazu Takahashi of the University of Tokyo. “Music exerts a strong appeal to the brain and has profound effects on emotion and cognition,” he added. While there have been previous demonstrations of animals dancing along to music – TikTok has a wealth of examples – the study is one of the first scientific investigations of the phenomenon. In the study, published in the journal Science Advances, 10 rats were fitted with wireless, miniature accelerometers to measure the slightest head movements. They were then played one-minute excerpts from Mozart’s Sonata for Two Pianos in D Major, at four different tempos: 75%, 100%, 200% and 400% of the original speed. Twenty human volunteers also participated. The scientists thought it possible that rats would prefer faster music as their bodies, including heartbeat, work at a faster pace. By contrast, the time constant of the brain is surprisingly similar across species. © 2022 Guardian News & Media Limited

Keyword: Hearing
Link ID: 28547 - Posted: 11.13.2022

By Elena Renken The brain’s lifeline, its network of blood vessels, is like a tree, says Mathieu Pernot, deputy director of the Physics for Medicine Paris Lab. The trunk begins in the neck with the carotid arteries, a pair of broad channels that then split into branches that climb into the various lobes of the brain. These channels fork endlessly into a web of tiny vessels that form a kind of canopy. The narrowest of these vessels are only wide enough for a single red blood cell to pass through, and in one important sense these vessels are akin to the tree’s leaves. “When you want to look at pathology, usually you don’t see the sickness in the tree, but in the leaves,” Pernot says. (You can identify Dutch Elm Disease when the tree’s leaves yellow and wilt.) Just like leaves, the tiniest blood vessels in the brain often register changes in neuron and synapse activity first, including illness, such as new growth in a cancerous brain tumor.1, 2 But only in the past decade or so have we developed the technology to detect these microscopic changes in blood flow: It’s called ultrafast ultrasound. Standard ultrasound is already popular in clinical imaging given that it is minimally invasive, low-cost, portable, and can generate images in real time.3 But until now, it has rarely been used to image the brain. That’s partly because the skull gets in the way—bone tends to scatter ultrasound waves—and the technology is too slow to detect blood flow in the smaller arteries that support most brain function. Neurologists have mostly used it in niche applications: to examine newborns, whose skulls have gaps between the bone plates, or to guide surgeons in some brain surgeries, where part of the skull is typically removed. Neuroscience researchers have also used it to study functional differences between the two hemispheres of the brain, based on imaging of the major cerebral arteries, by positioning the device over the temporal bone window, the thinnest area of the skull. © 2022 NautilusThink Inc,

Keyword: Brain imaging; Hearing
Link ID: 28536 - Posted: 11.02.2022

Elizabeth Pennisi Think of the chattiest creatures in the animal kingdom and songbirds, dolphins, and—yes—humans probably come to mind. Turtles probably don’t register. But these charismatic reptiles also communicate using a large repertoire of clicks, snorts, and chortles. Now, by recording the “voices” of turtles and other supposedly quiet animals, scientists have concluded that all land vertebrate vocalizations—from the canary’s song to the lion’s roar—have a common root that dates back more than 400 million years. The findings imply animals began to vocalize very early in their evolutionary history—even before they possessed well-developed ears, says W. Tecumseh Fitch, a bioacoustician at the University of Vienna who was not involved with the work. “It suggests our ears evolved to hear these vocalizations.” Several years ago, University of Arizona evolutionary ecologist John Wiens and his graduate student Zhuo Chen started looking into the evolutionary roots of acoustic communication—basically defined as the sounds animals make with their mouths using their lungs. Combing the scientific literature, the duo compiled a family tree of all the acoustic animals known at the time, eventually concluding such soundmaking abilities arose multiple times in vertebrates between 100 million and 200 million years ago. But Gabriel Jorgewich-Cohen, an evolutionary biologist at the University of Zürich, noticed an oversight: turtles. Though Wiens and Chen had found that only two of 14 families of turtles made sounds, he was finding a lot more. He spent 2 years recording 50 turtle species in the act of “speaking.”

Keyword: Hearing; Evolution
Link ID: 28530 - Posted: 10.28.2022

By Diana Kwon A Scottish woman named Joy Milne made headlines in 2015 for an unusual talent: her ability to sniff out people afflicted with Parkinson’s disease, a progressive neurodegenerative illness that is estimated to affect nearly a million people in the U.S. alone. Since then a group of scientists in the U.K. has been working with Milne to pinpoint the molecules that give Parkinson’s its distinct olfactory signature. The team has now zeroed in on a set of molecules specific to the disease—and has created a simple skin-swab-based test to detect them. Milne, a 72-year-old retired nurse from Perth, Scotland, has hereditary hyperosmia, a condition that endows people with a hypersensitivity to smell. She discovered that she could sense Parkinson’s with her nose after noticing her late husband, Les, was emitting a musky odor that she had not detected before. Eventually, she linked this change in scent to Parkinson’s when he was diagnosed with the disease many years later. Les passed away in 2015. In 2012 Milne met Tilo Kunath, a neuroscientist at the University of Edinburgh in Scotland, at an event organized by the research and support charity Parkinson’s UK. Although skeptical at first, Kunath and his colleagues decided to put Milne’s claims to the test. They gave her 12 T-shirts, six from people with Parkinson’s and six from healthy individuals. She correctly identified the disease in all six cases—and the one T-shirt from a healthy person she categorized as having Parkinson’s belonged to someone who went on to be diagnosed with the disease less than a year later. Advertisement Subsequently, Kunath, along with chemist Perdita Barran of the University of Manchester in England and her colleagues, has been searching for the molecules responsible for the change in smell that Milne can detect. The researchers used mass spectrometry to identify types and quantities of molecules in a sample of sebum, an oily substance found on the skin’s surface. They discovered changes to fatty molecules known as lipids in people with Parkinson’s. © 2022 Scientific American

Keyword: Chemical Senses (Smell & Taste); Parkinsons
Link ID: 28510 - Posted: 10.13.2022

By Paula Span The world of hearing health will change on Oct. 17, when the Food and Drug Administration’s new regulations, announced in August, will make quality hearing aids an over-the-counter product. It just won’t transform as quickly or as dramatically, at least at first, as advocates, technology and consumer electronics companies and people with mild to moderate hearing loss have been hoping. “It finally, actually happened after all these years,” said Dr. Frank Lin, the director of the Johns Hopkins Cochlear Center for Hearing and Public Health and a longtime supporter of the regulations, which Congress authorized five years ago. “Ninety-plus percent of adults with hearing loss have needs that can be served by over-the-counter hearing aids,” he said. For decades, the sale of hearing aids was restricted to licensed audiologists and other professionals; that has kept prices high — prescription hearing aids can cost $4,000 to $5,000 — and access limited. In contrast, the regulations provide “a clear glide path for new companies to enter this field,” Dr. Lin said. But, he quickly added, “it may be the Wild West for the next few years.” Barbara Kelley, the executive director of the Hearing Loss Association of America, concurred: “It’s a new frontier, and it is confusing. We need time to see how the market settles out.” In an ideal scenario, a person would be able to walk into almost any pharmacy or big-box store and buy a sophisticated pair of hearing aids for a few hundred dollars, no prescription required. But the shift won’t materialize right away, experts say. In 2017, Congress granted the F.D.A. three years to develop standards for safe and effective over-the-counter hearing aids. The agency took five years instead, and the long delay and continued industry opposition made manufacturers skittish about investing, Dr. Lin said. © 2022 The New York Times Company

Keyword: Hearing
Link ID: 28509 - Posted: 10.13.2022

Nicola Davis Science correspondent Whether it’s a tricky maths problem or an unexpected bill, daily life is full of stressful experiences. Now researchers have found that humans produce a different odour when under pressure – and dogs can sniff it out. While previous studies have suggested canines might pick up on human emotions, possibly through smell, questions remained over whether they could detect stress and if this could be done through scent. “This study has definitively proven that people, when they have a stress response, their odour profile changes,” said Clara Wilson, a PhD student at Queen’s University Belfast, and first author of the research. Wilson added the findings could prove useful when training service dogs, such as those that support people with post-raumatic stress disorder (PTSD). “They’re often trained to look at someone either crouching down on the floor, or starting to do self-injurious behaviours,” said Wilson.. The latest study, she said, offers another potential cue. “There is definitely a smell component, and that might be valuable in the training of these dogs in addition to all of the visual stuff,” said Wilson. Writing in the journal Plos One, Wilson and colleagues report how they first constructed a stand bearing three containers, each topped by a perforated lid. The researchers report they were able to train four dogs to indicate the container holding a particular breath and sweat sample, even when the line-up included unused gauze, samples from another person, or samples from the same person taken at a different time of day. © 2022 Guardian News & Media Limited

Keyword: Stress; Chemical Senses (Smell & Taste)
Link ID: 28498 - Posted: 10.01.2022

Nicola Davis Science correspondent If the taste of kale makes you screw up your face, you are not alone: researchers have observed foetuses pull a crying expression when exposed to the greens in the womb. While previous studies have suggested our food preferences may begin before birth and can be influenced by the mother’s diet, the team says the new research is the first to look directly at the response of unborn babies to different flavours. “[Previously researchers] just looked at what happens after birth in terms of what do [offspring] prefer, but actually seeing facial expressions of the foetus when they are getting hit by the bitter or by the non-bitter taste, that is something which is completely new,” said Prof Nadja Reissland, from Durham University, co-author of the research. Writing in the journal Psychological Science, the team noted that aromas from the mother’s diet were present in the amniotic fluid. Taste buds can detect taste-related chemicals from 14 weeks’ gestation, and odour molecules can be sensed from 24 weeks’ gestation. To delve into whether foetuses differentiate specific flavours, the team looked at ultrasound scans from almost 70 pregnant women, aged 18 to 40 from the north-east of England, who were split into two groups. One group was asked to take a capsule of powdered kale 20 minutes before an ultrasound scan, and the other was asked to take a capsule of powdered carrot. Vegetable consumption by the mothers did not differ between the kale and carrot group. The team also examined scans from 30 women, taken from an archive, who were not given any capsules. All the women were asked to refrain from eating anything else in the hour before their scans. The team then carried out a frame-by-frame analysis of the frequency of a host of different facial movements of the foetuses, including combinations that resembled laughing or crying. Overall, the researchers examined 180 scans from 99 foetuses, scanned at either 32 weeks, 36 weeks, or at both time points. © 2022 Guardian News & Media Limited

Keyword: Development of the Brain; Chemical Senses (Smell & Taste)
Link ID: 28493 - Posted: 09.28.2022

by Nora Bradford A well-studied brain response to sound, called the M100, appears earlier in life in autistic children than in their non-autistic peers, according to a new longitudinal study. The finding suggests that the auditory cortex in children with autism matures unusually quickly, a growth pattern seen previously in other brain regions. “It’s a demonstration that when we look for autism markers in the brain, they can be very age-specific,” says lead investigator J. Christopher Edgar, associate professor of radiology at the Children’s Hospital of Philadelphia in Pennsylvania. For that reason, longitudinal studies such as this one — in which Edgar and his colleagues assessed children at up to three different ages — are essential, he adds. “If the two populations being studied have different rates of brain maturation, then the pattern of findings changes across time.” At the time of the first magnetoencephalography (MEG) scan, when the children were 6 to 9 years old, those with autism were more likely to have an M100 response to a barely audible tone in the right hemisphere than non-autistic children were. But this difference disappeared in the next two visits, presumably because the M100 response typically appears during early adolescence. By contrast, the M50 response, which occurs throughout life, beginning in utero, showed no significant difference between the two groups at any visit. The team also evaluated ‘phase locking,’ a measure of how similar a participant’s neural activity is from scan to scan within a certain frequency band. Autistic participants demonstrated more mature phase-locking patterns at the first visit, which then diminished at the later two visits. © 2022 Simons Foundation

Keyword: Autism; Hearing
Link ID: 28478 - Posted: 09.17.2022

By Erin Garcia de Jesús Some mosquitoes have a near-foolproof thirst for human blood. Previous attempts to prevent the insects from tracking people down by blocking part of mosquitoes’ ability to smell have failed. A new study hints it’s because the bloodsuckers have built-in workarounds to ensure they can always smell us. For most animals, individual nerve cells in the olfactory system can detect just one type of odor. But Aedes aegypti mosquitoes’ nerve cells can each detect many smells, researchers report August 18 in Cell. That means if a cell were to lose the ability to detect one human odor, it still can pick up on other scents. The study provides the most detailed map yet of a mosquito’s sense of smell and suggests that concealing human aromas from the insects could be more complicated than researchers thought. Repellents that block mosquitoes from detecting human-associated scents could be especially tricky to make. “Maybe instead of trying to mask them from finding us, it would be better to find odorants that mosquitoes don’t like to smell,” says Anandasankar Ray, a neuroscientist at the University of California, Riverside who was not involved in the work. Such repellents may confuse or irritate the bloodsuckers and send them flying away (SN: 9/21/11; SN: 3/4/21). Effective repellents are a key tool to prevent mosquitoes from transmitting disease-causing viruses such as dengue and Zika (SN: 7/11/22). “Mosquitoes are responsible for more human deaths than any other creature,” says Olivia Goldman, a neurobiologist at Rockefeller University in New York City. “The better we understand them, the better that we can have these interventions.” © Society for Science & the Public 2000–2022.

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 28439 - Posted: 08.20.2022

By Carolyn Gramling Hot or not? Peeking inside an animal’s ear — even a fossilized one — may tell you whether it was warm- or cold-blooded. Using a novel method that analyzes the size and shape of the inner ear canals, researchers suggest that mammal ancestors abruptly became warm-blooded about 233 million years ago, the team reports in Nature July 20. Warm-bloodedness, or endothermy, isn’t unique to mammals — birds, the only living dinosaurs, are warm-blooded, too. But endothermy is one of mammals’ key features, allowing the animals to regulate their internal body temperatures by controlling their metabolic rates. This feature allowed mammals to occupy environmental niches from pole to equator, and to weather the instability of ancient climates (SN: 6/7/22). When endothermy evolved, however, has been a mystery. Based on fossil analyses of growth rates and oxygen isotopes in bones, researchers have proposed dates for its emergence as far back as 300 million years ago. The inner ear structures of mammals and their ancestors hold the key to solving that mystery, says Ricardo Araújo, a vertebrate paleontologist at the University of Lisbon. In all vertebrates, the labyrinth of semicircular canals in the inner ear contains a fluid that responds to head movements, brushing against tiny hair cells in the ear and helping to maintain a sense of balance. That fluid can become thicker or thinner depending on body temperature. “Mammals have very unique inner ears,” Araújo says. Compared with cold-blooded vertebrates of similar size, the dimensions of mammals’ semicircular canals — such as thickness, length and radius of curvature — is particularly small, he says. “The ducts are very thin and tend to be very circular compared with other animals.” By contrast, fish have the largest for their body size. © Society for Science & the Public 2000–2022.

Keyword: Hearing; Evolution
Link ID: 28408 - Posted: 07.23.2022

By Stephanie Pappas As familiar to everyone as the COVID-causing coronavirus SARS-CoV-2 has become over the past two years, feverish research is still trying to parse a lingering puzzle. How, in fact, does the pandemic virus that has so changed the world cross over into the brain after entering the respiratory system? An answer is important because neurological complaints are some of the most common in the constellation of symptoms called long COVID. The mystery centers around the fact that brain cells don’t display the receptors, or docking sites, that the virus uses to get into nasal and lung cells. SARS-CoV-2, though, may have come up with an ingenious work-around. It may completely do away with the molecular maneuverings needed to attach to and unlock a cell membrane. Instead it wields a blunt instrument in the form of nanotube “bridges”—cylinders constructed of the common protein actin that are no more than a few tens of nanometers in diameter. These tunneling nanotubes extend across cell-to-cell gaps to penetrate a neighbor and give viral particles a direct route into COVID-impervious tissue. Researchers at the Pasteur Institute in Paris demonstrated the prospects for a nanotube-mediated cell crossing in a study in a lab dish that now needs to be confirmed in infected human patients. Given further proof, the findings could explain why some people who get COVID-19 experience brain fog and other neurological symptoms. Also, if the intercellular conduits could be severed, that might prevent some of these debilitating aftereffects of infection. The nanotube route “is a shortcut that propagates infection fast and between different organs, permissive or not permissive, to the infection,” says Chiara Zurzolo, a cell biologist at the Pasteur Institute, who conducted the study. “And it might be also a way for the virus to hide and escape the immune response.” © 2022 Scientific American

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28407 - Posted: 07.23.2022

By Laura Sanders A dog’s brain is wired for smell. Now, a new map shows just how extensive that wiring is. Powerful nerve connections link the dog nose to wide swaths of the brain, researchers report July 11 in the Journal of Neuroscience. One of these canine connections, a hefty link between areas that handle smell and vision, hasn’t been seen before in any species, including humans. The results offer a first-of-its-kind anatomical description of how dogs “see” the world with their noses. The new brain map is “awesome, foundational work,” says Eileen Jenkins, a retired army veterinarian and expert on working dogs. “To say that they have all these same connections that we have in humans, and then some more, it’s going to revolutionize how we understand cognition in dogs.” In some ways, the results aren’t surprising, says Pip Johnson, a veterinary radiologist and neuroimaging expert at Cornell University College of Veterinary Medicine. Dogs are superb sniffers. Their noses hold between 200 million and 1 billion odor molecule sensors, compared with the 5 million receptors estimated to dwell in a human nose. And dogs’ olfactory bulbs can be up to 30 times larger than people’s. But Johnson wanted to know how smell information wafts to brain regions beyond the obvious sniffing equipment. To build the map, Johnson and colleagues performed MRI scans on 20 mixed-breed dogs and three beagles. The subjects all had long noses and medium heads, and were all probably decent sniffers. Researchers then identified tracts of white matter fibers that carry signals between brain regions. A method called diffusion tensor imaging, which relies on the movement of water molecules along tissue, revealed the underlying tracts, which Johnson likens to the brain’s “road network.” © Society for Science & the Public 2000–2022.

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 28405 - Posted: 07.22.2022

By Veronique Greenwood Human beings maintain the polite fiction that we’re not constantly smelling one another. Despite our efforts to the contrary, we all have our own odors, pleasant and less so, and if we are like other land mammals, our particular perfume might mean something to our fellow humans. Some of these, like the reek of someone who hasn’t bathed all month, or the distinctive whiff of a toddler who is pretending they didn’t just fill their diaper, are self-explanatory. But scientists who study human olfaction, or your sense of smell, wonder if the molecules wafting off our skin may be registering at some subconscious level in the noses and brains of people around us. Are they bearing messages that we use in decisions without realizing it? Might they even be shaping whom we do and don’t like to spend time around? Indeed, in a small study published Wednesday in the journal Science Advances, researchers investigating pairs of friends whose friendship “clicked” from the beginning found intriguing evidence that each person’s body odor was closer to their friend’s than expected by chance. And when the researchers got pairs of strangers to play a game together, their body odors predicted whether they felt they had a good connection. There are many factors that shape whom people become friends with, including how, when or where we meet a new person. But perhaps one thing we pick up on, the researchers suggest, is how they smell. Scientists who study friendship have found that friends have more in common than strangers — not just things like age and hobbies, but also genetics, patterns of brain activity and appearance. Inbal Ravreby, a graduate student in the lab of Noam Sobel, an olfaction researcher at the Weizmann Institute of Science in Israel, was curious whether particularly swift friendships, the kind that seem to form in an instant, had an olfactory component — whether people might be picking up on similarities in their smells. © 2022 The New York Times Company

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 28382 - Posted: 06.25.2022

Michael Marshall Researchers are finally making headway in understanding how the SARS-CoV-2 coronavirus causes loss of smell. And a multitude of potential treatments to tackle the condition are undergoing clinical trials, including steroids and blood plasma. Once a tell-tale sign of COVID-19, smell disruption is becoming less common as the virus evolves. “Our inboxes are not as flooded as they used to be,” says Valentina Parma, a psychologist at the Monell Chemical Senses Center in Philadelphia, Pennsylvania, who helped field desperate inquiries from patients throughout the first two years of the pandemic. A study published last month1 surveyed 616,318 people in the United States who have had COVID-19. It found that, compared with those who had been infected with the original virus, people who had contracted the Alpha variant — the first variant of concern to arise — were 50% as likely to have chemosensory disruption. This probability fell to 44% for the later Delta variant, and to 17% for the latest variant, Omicron. But the news is not all good: a significant portion of people infected early in the pandemic still experience chemosensory effects. A 2021 study2 followed 100 people who had had mild cases of COVID-19 and 100 people who repeatedly tested negative. More than a year after their infections, 46% of those who had had COVID-19 still had smell problems; by contrast, just 10% of the control group had developed some smell loss, but for other reasons. Furthermore, 7% of those who had been infected still had total smell loss, or ‘anosmia’, at the end of the year. Given that more than 500 million cases of COVID-19 have been confirmed worldwide, tens of millions of people probably have lingering smell problems. For these people, help can’t come soon enough. Simple activities such as tasting food or smelling flowers are now “really emotionally distressing”, Parma says. © 2022 Springer Nature Limited

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28374 - Posted: 06.15.2022

By Tina Hesman Saey Dogs are as reliable as laboratory tests for detecting COVID-19 cases, and may be even better than PCR tests for identifying infected people who don’t have symptoms. A bonus: The canines are cuter and less invasive than a swab up the nose. In a study involving sweat samples from 335 people, trained dogs sniffed out 97 percent of the coronavirus cases that had been identified by PCR tests, researchers report June 1 in PLOS One. And the dogs found all 31 COVID-19 cases among 192 people who didn’t have symptoms. These findings are evidence that dogs could be effective for mass screening efforts at places such as airports or concerts and may provide friendly alternatives for testing people who balk at nasal swabs, says Dominique Grandjean, a veterinarian at the National School of Veterinary Medicine of Alfort in Maisons-Alfort, France. “The dog doesn’t lie,” but there are many ways PCR tests can go wrong, Grandjean says. The canines’ noses also identified more COVID-19 cases than did antigen tests (SN: 12/17/21), similar to many at-home tests, but sometimes mistook another respiratory virus for the coronavirus, Grandjean and colleagues found. What’s more, anecdotal evidence suggests the dogs can pick up asymptomatic cases as much as 48 hours before people test positive by PCR, he says. In the study, dogs from French fire stations and from the Ministry of the Interior of the United Arab Emirates were trained in coronavirus detection by rewarding them with toys — usually tennis balls. “It’s playtime for them,” Grandjean says. It takes about three to six weeks, depending on the dog’s experience with odor detection, to train a dog to pick out COVID-19 cases from sweat samples. © Society for Science & the Public 2000–2022.

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28349 - Posted: 06.04.2022

Freda Kreier Some bats can imitate the sound of buzzing hornets to scare off owls, researchers say. The discovery is the first documented case of a mammal mimicking an insect to deter predators. Many animals copy other creatures in a bid to make themselves seem less palatable to predators. Most of these imitations are visual. North America’s non-venomous scarlet kingsnake (Lampropeltis elapsoides), for instance, has evolved to have similar colour-coding to the decidedly more dangerous eastern coral snake (Micrurus fulvius). Now, a study comparing the behaviour of owls exposed to insect and bat noises suggests that greater mouse-eared bats (Myotis myotis) might be among the few animals to have weaponized another species’ sound, says co-author Danilo Russo, an animal ecologist at the University of Naples Federico II in Italy. “When we think of mimicry, the first thing that comes to mind is colour, but in this case, it is sound that plays a crucial role,” he adds. The research was published on 9 May in Current Biology1. Because they are nocturnal and have poor eyesight, most bats rely on echolocation to find their way around, and communicate using a wide array of other noises. Russo first noticed that the distress call of the greater mouse-eared bat sounded like the buzzing of bees or hornets while he was catching the bats for a different research project. To investigate whether other animals might make the same connection, Russo and his colleagues compared the sound structure of buzzing by the European hornet (Vespa crabro) to that of the bat’s distress call. At most frequencies, the two sounds were not dramatically similar, but they were when the bat’s call was stripped down to include only frequencies that owls — one of the animal’s main predators — are able to hear. This suggests that the distress call as heard by owls strongly resembles the buzzing of a hornet, Russo says, so it could fool predators. © 2022 Springer Nature Limited

Keyword: Hearing; Evolution
Link ID: 28324 - Posted: 05.11.2022

Neuroscience researchers have found a master gene that controls the development of special sensory cells in the ears – potentially opening the door to reversing hearing loss. A team led by Jaime García-Añoveros of Northwestern University, US, established that a gene called Tbx2 controls the development of ear hair cells in mice. The findings of their study are published today in Nature. What are hair cells? Hair cells are the sensory cells in our ears that detect sound and then transmit a message to our brains. They are so named because they have tiny hairlike structures called stereocilia. “The ear is a beautiful organ,” says García-Añoveros. “There is no other organ in a mammal where the cells are so precisely positioned.” Hair cells are found in a structure called the organ of Corti, in the cochlea in the inner ear. The organ of Corti sits on top of the basilar membrane. Sound waves are funnelled through our ear canal and cause the eardrum (also known as the tympanic membrane) and ossicles (tiny bones called the malleus, incus and stapes) to vibrate. The vibrations, or waves, are transmitted through fluid in the cochlea, causing the basilar membrane to move as well. When the basilar membrane moves, the stereocilia tilt, causing ion channels in the hair cell membrane to open. This stimulates the hair cell to release neurotransmitter chemicals, which will transmit the sound signal to the brain via the auditory nerve.

Keyword: Hearing; Regeneration
Link ID: 28319 - Posted: 05.07.2022

By Sabrina Imbler Sign up for Science Times Get stories that capture the wonders of nature, the cosmos and the human body. Get it sent to your inbox. One morning in the Panamanian rainforest, a small fruit bat sized up his competition. The odds did not appear to be in his favor. The winged mammal, a Seba’s short-tailed bat, weighed about half an ounce. But his six opponents, fringe-lipped bats, were twice as heavy and occupying the shrouded corner where the small bat wanted to roost. Even worse, the larger bats are known to feast on small animals, such as frogs, katydids and smaller bats — including Seba’s short-tailed bats. None of this fazed the Seba’s short-tailed bat, which proceeded to scream, shake his wings and hurl his body at the posse of bigger bats, slapping one in the face more than 50 times. “I’ve never seen anything like it,” said Ahana Aurora Fernandez, a behavioral biologist at the Natural History Museum, Berlin, who viewed a recording of the bats but was not involved in the research that produced it. “It’s one bat against six,” Dr. Fernandez said. “He shows no fear at all.” The tiny bat’s belligerence paid off as the big bats fled. The corner clear, the Seba’s short-tailed bat moved in, joined a minute later by his female companion, who had nonchalantly watched the fight from nearby. This fun-size brawl and two similar bat bullying incidents in other roosts were observed by Mariana Muñoz-Romo, a biologist at the Smithsonian Tropical Research Institute, and her colleagues, who had been monitoring the sexual preferences of the larger fringe-lipped bats. In a paper published in March in the journal Behaviour, they asked how often tiny bats antagonize bigger ones. When it comes with a risk of being eaten, why pick a fight? The researchers originally set out to study fringe-lipped bats, who were recently discovered to smear a sticky, fragrant substance on their arms, potentially to attract mates. The animals also have impressive appetites, and have been observed eating sizable frogs. © 2022 The New York Times Company

Keyword: Aggression; Hearing
Link ID: 28287 - Posted: 04.16.2022

By Sharon Oosthoek Despite their excellent vision, one city-dwelling colony of fruit bats echolocates during broad daylight — completely contrary to what experts expected. A group of Egyptian fruit bats (Rousettus aegyptiacus) in downtown Tel Aviv uses sound to navigate in the middle of the day, researchers report in the April 11 Current Biology. The finding greatly extends the hours during which bats from this colony echolocate. A few years ago, some team members had noticed bats clicking while they flew under low-light conditions. The midday sound-off seems to help the bats forage and navigate, even though they can see just fine. Bats that are active during the day are unusual. Out of the more than 1,400 species, roughly 10 are diurnal. What’s more, most diurnal bats don’t use echolocation during the day, relying instead on their vision to forage and avoid obstacles. They save echolocation for dim light or dark conditions. So that’s why, two years ago, a group of Tel Aviv researchers were surprised when they noticed a bat smiling during the day. They were looking over photos from their latest study of Egyptian fruit bats when they noticed one with its mouth slightly parted and upturned. “When an Egyptian fruit bat is smiling, he’s echolocating — he’s producing clicks with his tongue and his mouth is open,” says Ofri Eitan, a bat researcher at Tel Aviv University. “But this was during the day, and these bats see really well.” When Eitan and his colleagues looked through other photos — thousands of them — many showed smiling bats in broad daylight. The team showed in 2015 that the diurnal Egyptian fruit bats do use echolocation outdoors under various low light conditions, at least occasionally. But the researchers hadn’t looked at whether the bats were echolocating during midday hours when light levels are highest. © Society for Science & the Public 2000–2022.

Keyword: Hearing; Evolution
Link ID: 28286 - Posted: 04.16.2022

Dustin Jones Researchers from Sweden and the United Kingdom teamed up to sniff out the answer to a question practically every person has pondered at one time or another: what is the best smell out there? They found that most people, despite coming from different cultures and backgrounds, find vanilla to be the most pleasant smell on the planet more often than not. Sour, stinky feet? Not so much. The collaborative study between Sweden's Karolinska Institutet and the University of Oxford found that people share similar preferences when it comes to smell, regardless of cultural background. And according to the results, vanilla is the most pleasing smell around, followed by ethyl butyrate, which smells like peaches. Artin Arshamian, researcher at Karolinska and one of the study's authors, said humans may have similar olfactory preferences because it helped early humans survive. Which may very well explain why stinky feet came in dead last as far as appealing odors are concerned. According to the study, the pleasantness of a smell can be attributed to the structure of an edible item's odor molecule 41% of the time. Simply put, humans likely enjoy many of the same smells, more often than not, because of a deep-rooted sense that an item is safe to eat. Sponsor Message "We wanted to examine if people around the world have the same smell perception and like the same types of [odor], or whether this is something that is culturally learned," Arshamian said. "Traditionally it has been seen as cultural, but we can show that culture has very little to do with it." © 2022 npr

Keyword: Chemical Senses (Smell & Taste)
Link ID: 28268 - Posted: 04.06.2022