Chapter 9. Hearing, Vestibular Perception, Taste, and Smell

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Susan Milius Sonar pings from a hungry bat closing in can inspire hawkmoths to get their genitals trilling. The ultrasonic “eeeee” of scraping moth sex organs may serve as a last-second acoustic defense, says behavioral ecologist Jesse Barber of Boise State University in Idaho. In theory, the right squeak could jam bats’ targeting sonar, remind them of a noisy moth that tasted terrible or just startle them enough for the hawkmoth to escape. Males of at least three hawkmoth species in Malaysia squeak in response to recorded echolocation sounds of the final swoop in a bat attack, Barber and Akito Kawahara of the University of Florida in Gainesville report July 3 in Biology Letters. Female hawkmoths are hard to catch, but the few Barber and Kawahara have tested squeak too. Although they’re the same species as the males, they use their genitals in a different way to make ultrasound. Squeak power may have arisen during courtship and later proved useful during attacks. Until now, researchers knew of only two insect groups that talk back to bats: some tiger moths and tiger beetles. Neither is closely related to hawkmoths, so Barber speculates that anti-bat noises might be widespread among insects. Slowed-down video shows first the male and then the female hawkmoth creating ultrasonic trills at the tips of their abdomens. Males use a pair of claspers that grasp females in mating. To sound off, these quickly slide in and out of the abdomen, rasping specialized scales against the sides. Females rub the left and right sides of their abdominal structures together. J. Barber and A.Y. Kawahara. Hawkmoths produce anti-bat ultrasound. Biology Letters. Posted July 3, 2013. doi: 10.1098/rsbl.2013.0161 [Go to] |© Society for Science & the Public 2000 - 2017.

Keyword: Hearing
Link ID: 23864 - Posted: 07.24.2017

By Aylin Woodward See, hear. Our eardrums appear to move to shift our hearing in the same direction as our eyes are looking. Why this happens is unclear, but it may help us work out which objects we see are responsible for the sounds we can hear. Jennifer Groh at Duke University in Durham, North Carolina, and her team have been using microphones inserted into people’s ears to study how their eardrums change during saccades – the movement that occurs when we shift visual focus from one place to another. You won’t notice it, but our eyes go through several saccades a second to take in our surroundings. Examining 16 people, the team detected changes in ear canal pressure that were probably caused by middle-ear muscles tugging on the eardrum. These pressure changes indicate that when we look left, for example, the drum of our left ear gets pulled further into the ear and that of our right ear pushed out, before they both swing back and forth a few times. These changes to the eardrums began as early as 10 milliseconds before the eyes even started to move, and continued for a few tens of milliseconds after the eyes stopped. Making sense “We think that before actual eye movement occurs, the brain sends a signal to the ear to say ‘I have commanded the eyes to move 12 degrees to the right’,” says Groh. The eardrum movements that follow the change in focus may prepare our ears to hear sounds from a particular direction. © Copyright New Scientist Ltd.

Keyword: Hearing; Vision
Link ID: 23860 - Posted: 07.22.2017

by Laurel Hamers The tempo of a male elephant seal’s call broadcasts his identity to rival males, a new study finds. Every male elephant seal has a distinct vocalization that sounds something like a sputtering lawnmower — pulses of sound in a pattern and at a pace that stays the same over time. At a California state park where elephant seals breed each year, researchers played different variations of an alpha male’s threat call to subordinate males who knew him. The seals weren’t as responsive when the tempo of that call was modified substantially, suggesting they didn’t recognize it as a threat. Modifying the call’s timbre — the acoustic quality of the sound — had the same effect, researchers report August 7 in Current Biology. Unlike dolphins and songbirds, elephant seals don’t seem to vary pitch to communicate. Those vocal name tags serve a purpose. During breeding season, male elephant seals spend three months on land without food or water, competing with rivals for social status and mating rights. Fights between two blubbery car-sized animals can be brutal. “We’ve seen males lose their noses,” says Caroline Casey, a biologist at the University of California, Santa Cruz. For lower-ranking males, identifying an alpha male by his call and then backing off might prevent a beach brawl. |© Society for Science & the Public 2000 - 2017

Keyword: Animal Communication; Sexual Behavior
Link ID: 23859 - Posted: 07.21.2017

Nicola Davis People who experience hearing loss could be at greater risk of memory and thinking problems later in life than those without auditory issues, research suggests. The study focused on people who were at risk of Alzheimer’s disease, revealing that those who were diagnosed with hearing loss had a higher risk of “mild cognitive impairment” four years later. “It’s really not mild,” said Clive Ballard, professor of age-related disease at the University of Exeter. “They are in the lowest 5% of cognitive performance and about 50% of those individuals will go on to develop dementia.” Guardian Morning Briefing - sign up and start the day one step ahead Read more Presented at the Alzheimer’s Association International Conference in London, researchers from the US looked at the memory and thinking skills of 783 cognitively healthy participants in late middle age, more than two-thirds of whom had at least one parent who had been diagnosed with Alzheimer’s disease. The team carried out a range of cognitive tests on the participants over a four-year period, aimed at probing memory and mental processing, revealing that those who had hearing loss at the start of the study were more than twice as likely to be found to have mild cognitive impairment four years later than those with no auditory problems, once a variety of other risk factors were taken into account. Taylor Fields, a PhD student at the University of Wisconsin who led the research, said that the findings suggest hearing loss could be an early warning sign that an individual might be at greater risk of future cognitive impairment - but added more research was necessary to unpick the link. “There is something here and it should be looked into,” she said. © 2017 Guardian News and Media Limited

Keyword: Hearing; Alzheimers
Link ID: 23840 - Posted: 07.17.2017

By Mitch Leslie When you have a stuffy nose, a slice of freshly baked apple pie tastes like mush. But not being able to smell your food could have a surprising effect on your metabolism, potentially helping you remain thin even when you eat fatty foods, a new study in mice suggests. “This is a very exciting study, and the outcome is quite compelling,” says neuroendocrinologist Tamas Horvath of Yale School of Medicine, who wasn’t connected to the research. To conduct the study, molecular biologist Andrew Dillin of the University of California, Berkeley, and colleagues turned to a variety of genetically altered mice. The scientists gave them regular doses of the diphtheria toxin—which causes a temporary loss of odor-sensing neurons—to suppress their sense of smell. They then fed the rodents either a normal diet or fatty foods—the mouse equivalent of cheesecake and pizza—that usually induce obesity. After more than 3 months of noshing on regular chow, the odor-deprived rodents weighed slightly less than mice whose sense of smell was intact. In the group on the high-fat diet, however, the mice that couldn’t smell weighed 16% less than animals that could, which became obese. Losing the ability to smell also caused a different group of already-obese mice to lose weight, the researchers reveal today in Cell Metabolism. © 2017 American Association for the Advancement of Science.

Keyword: Obesity; Chemical Senses (Smell & Taste)
Link ID: 23810 - Posted: 07.06.2017

By Mo Costandi You can’t teach an old dog new tricks—or can you? Textbooks tell us that early infancy offers a narrow window of opportunity during which sensory experience shapes the way neuronal circuits wire up to process sound and other inputs. A lack of proper stimulation during this “critical period” has a permanent and detrimental effect on brain development. But new research shows the auditory system in the adult mouse brain can be induced to revert to an immature state similar to that in early infancy, improving the animals’ ability to learn new sounds. The findings, published Thursday in Science, suggest potential new ways of restoring brain function in human patients with neurological diseases—and of improving adults’ ability to learn languages and musical instruments. In mice, a critical period occurs during which neurons in a portion of the brain’s wrinkled outer surface, the cortex, are highly sensitized to processing sound. This state of plasticity allows them to strengthen certain connections within brain circuits, fine-tuning their auditory responses and enhancing their ability to discriminate between different tones. In humans, a comparable critical period may mark the beginning of language acquisition. But heightened plasticity declines rapidly, and this continues throughout life, making it increasingly difficult to learn. In 2011 Jay Blundon, a developmental neurobiologist at Saint Jude Children's Research Hospital, and his colleagues reported that the critical periods for circuits connecting the auditory cortex and the thalamus occur at about the same time. © 2017 Scientific American,

Keyword: Hearing; Development of the Brain
Link ID: 23793 - Posted: 06.30.2017

By STEPH YIN Whales and songbirds produce sounds resembling human music, and chimpanzees and crows use tools. But only one nonhuman animal is known to marry these two skills. Palm cockatoos from northern Australia modify sticks and pods and use them to drum regular rhythms, according to new research published in Science Advances on Wednesday. In most cases, males drop beats in the presence of females, suggesting they perform the skill to show off to mates. The birds even have their own signature cadences, not unlike human musicians. This example is “the closest we have so far to musical instrument use and rhythm in humans,” said Robert Heinsohn, a professor of evolutionary and conservation biology at the Australian National University and an author of the paper. A palm cockatoo drumming performance starts with instrument fashioning — an opportunity to show off beak strength and cleverness (the birds are incredibly intelligent). Often, as a female is watching, a male will ostentatiously break a hefty stick off a tree and trim it to about the length of a pencil. Holding the stick, or occasionally a hard seedpod, with his left foot (parrots are typically left-footed), the male taps a beat on his tree perch. Occasionally he mixes in a whistle or other sounds from an impressive repertoire of around 20 syllables. As he grows more aroused, the crest feathers on his head become erect. Spreading his wings, he pirouettes and bobs his head deeply, like an expressive pianist. He uncovers his red cheek patches — the only swaths of color on his otherwise black body — and they fill with blood, brightening like a blush. Over seven years, Dr. Heinsohn and his collaborators collected audio and video recordings of 18 male palm cockatoos exhibiting such behaviors in Australia’s Cape York Peninsula, where the birds are considered vulnerable because of aluminum ore mining. © 2017 The New York Times Company

Keyword: Animal Communication; Sexual Behavior
Link ID: 23790 - Posted: 06.29.2017

Elizabeth Hellmuth Margulis Whether tapping a foot to samba or weeping at a ballad, the human response to music seems almost instinctual. Yet few can articulate how music works. How do strings of sounds trigger emotion, inspire ideas, even define identities? Cognitive scientists, anthropologists, biologists and musicologists have all taken a crack at that question (see go.nature.com/2sdpcb5), and it is into this line that Adam Ockelford steps. Comparing Notes draws on his experience as a composer, pianist, music researcher and, most notably, a music educator working for decades with children who have visual impairments or are on the autistic spectrum, many with extraordinary musical abilities. Through this “prism of the overtly remarkable”, Ockelford seeks to shed light on music perception and cognition in all of us. Existing models based on neurotypical children could overlook larger truths about the human capacity to learn and make sense of music he contends. Some of the children described in Comparing Notes might (for a range of reasons) have trouble tying their shoelaces or carrying on a basic conversation. Yet before they hit double digits in age, they can hear a complex composition for the first time and immediately play it on the piano, their fingers flying to the correct notes. This skill, Ockelford reminds us, eludes many adults with whom he studied at London's Royal Academy of Music. Weaving together the strands that let these children perform such stunning feats, Ockelford constructs an argument for rethinking conventional wisdom on music education. He positions absolute pitch (AP) as central to these abilities to improvise, listen and play. © 2017 Macmillan Publishers Limited,

Keyword: Hearing
Link ID: 23744 - Posted: 06.15.2017

Paula Span A few years hence, when you’ve finally tired of turning up the TV volume and making dinner reservations at 5:30 p.m. because any later and the place gets too loud, you may go shopping. Perhaps you’ll head to a local boutique called The Hear Better Store, or maybe Didja Ear That? (Reader nominees for kitschy names invited.) Maybe you’ll opt for a big-box retailer or a kiosk at your local pharmacy. If legislation now making its way through Congress succeeds, these places will all offer hearing aids. You’ll try out various models — they’ll all meet newly established federal requirements — to see what seems to work and feel best. Your choices might include products from big consumer electronics specialists like Apple, Samsung and Bose. If you want assistance, you might pay an audiologist to provide customized services, like adjusting frequencies or amplification levels. But you won’t need to go through an audiologist-gatekeeper, as you do now, to buy hearing aids. The best part of this over-the-counter scenario: Instead of spending an average of $1,500 to $2,000 per device (and nearly everyone needs two), you’ll find that the price has plummeted. You might pay $300 per ear, maybe even less. So many people will be using these new over-the-counter hearing aids — along with the hordes wearing earbuds for other reasons — that you won’t feel self-conscious. You’ll blend right in. That, at least, represents the future envisioned by supporters of the Over-the-Counter Hearing Aid Act of 2017, which would give the Food and Drug Administration three years to create a regulatory category for such devices and to establish standards for safety, effectiveness and labeling.

Keyword: Hearing
Link ID: 23736 - Posted: 06.13.2017

By David Noonan Sight and hearing get all the glory, but the often overlooked and underappreciated sense of smell—or problems with it—is a subject of rapidly growing interest among scientists and clinicians who battle Alzheimer’s and Parkinson’s diseases. Impaired smell is one of the earliest and most common symptoms of both, and researchers hope a better understanding will improve diagnosis and help unlock some of the secrets of these incurable conditions. The latest offering from the burgeoning field is a paper published this month in Lancet Neurology. It proposes neurotransmitter dysfunction as a possible cause of smell loss in a number of neurodegenerative diseases, including Alzheimer’s and Parkinson’s. More than 90 percent of Parkinson’s patients report some level of olfactory dysfunction. And because problems with smell progress in Alzheimer’s, nearly all of those diagnosed with moderate to severe forms of the illness have odor identification issues. “It’s important, not just because it’s novel and interesting and simple but because the evidence is strong,” says Davangere Devanand, a professor of psychiatry and neurology at Columbia University. His most recent paper on the subject, a review, was published in The American Journal of Geriatric Psychiatry in December. Studies have shown impaired smell to be even stronger than memory problems as a predictor of cognitive decline in currently healthy adults. It is especially useful for forecasting the progression from mild cognitive impairment (MCI) to full-blown Alzheimer’s. According to the Alzheimer’s Association, approximately 15 to 20 percent of people over 65 have MCI. About half of them go on to develop Alzheimer’s, Devanand says—and the sooner they are identified, the earlier doctors can begin interventions, including treatment with the few existing Alzheimer’s drugs. © 2017 Scientific American

Keyword: Alzheimers; Chemical Senses (Smell & Taste)
Link ID: 23729 - Posted: 06.12.2017

By Emily Underwood Viewed under a microscope, your tongue is an alien landscape, studded by fringed and bumpy buds that sense five basic tastes: salty, sour, sweet, bitter, and umami. But mammalian taste buds may have an additional sixth sense—for water, a new study suggests. The finding could help explain how animals can tell water from other fluids, and it adds new fodder to a centuries-old debate: Does water have a taste of its own, or is it a mere vehicle for other flavors? Ever since antiquity, philosophers have claimed that water has no flavor. Even Aristotle referred to it as “tasteless” around 330 B.C.E. But insects and amphibians have water-sensing nerve cells, and there is growing evidence of similar cells in mammals, says Patricia Di Lorenzo, a behavioral neuroscientist at the State University of New York in Binghamton. A few recent brain scan studies also suggest that a region of human cortex responds specifically to water, she says. Still, critics argue that any perceived flavor is just the after-effect of whatever we tasted earlier, such as the sweetness of water after we eat salty food. “Almost nothing is known” about the molecular and cellular mechanism by which water is detected in the mouth and throat, and the neural pathway by which that signal is transmitted to the brain, says Zachary Knight, a neuroscientist at the University of California, San Francisco. In previous studies, Knight and other researchers have found distinct populations of neurons within a region of the brain called the hypothalamus that can trigger thirst and signal when an animal should start and stop drinking. But the brain must receive information about water from the mouth and tongue, because animals stop drinking long before signals from the gut or blood could tell the brain that the body has been replenished, he says. © 2017 American Association for the Advancement of Science. A

Keyword: Chemical Senses (Smell & Taste)
Link ID: 23680 - Posted: 05.31.2017

By Bob Holmes As soon as I decided to write a book on the science of flavor, I knew I wanted to have myself genotyped. Every one of us, I learned through my preliminary research for Flavor: The Science of Our Most Neglected Sense, probably has a unique set of genes for taste and odor receptors. So each person lives in their own flavor world. I wanted to know what my genes said about my own world. Sure enough, there was a lesson there—but not the one I expected. Our senses of smell and taste detect chemicals in the environment as they bind to receptors on the olfactory epithelium in the nose or on taste buds studding the mouth. From these two inputs, plus a few others, the brain assembles the compound perception we call flavor. Taste is pretty simple: basically, one receptor type each for sweet, sour, salty, and the savory taste called umami, and a family of maybe 20 or more bitter receptors, each of which is sensitive to different chemicals. Smell, on the other hand, relies on more than 400 different odor receptor types, the largest gene family in the human genome. Variation in any of these genes—and, probably, many other genes that affect the pathways involved in taste or smell—should affect how we perceive the flavors of what we eat and drink. Hence the genotyping. One April morning a few years ago, I drooled into a vial and sent that DNA sample off to the Monell Chemical Senses Center in Philadelphia, home to what is likely the world’s biggest research group dedicated to the basic science of flavor. A few months later, I visited Monell to take a panel of perceptual tests and compare the results to my genetic profile. © 1986-2017 The Scientist

Keyword: Chemical Senses (Smell & Taste)
Link ID: 23652 - Posted: 05.24.2017

By Lindzi Wessel You’ve probably heard that your sense of smell isn’t that great. After all, compared with a dog or even a mouse, the human olfactory system doesn’t take up that much space. And when was the last time you went sniffing the ground alongside your canine companion? But now, in a new review published today in Science, neuroscientist John McGann of Rutgers University in New Brunswick, New Jersey, argues that the myth of the nonessential nose is a huge mistake—one that has led scientists to neglect research in a critical and mysterious part of our minds. Science checked in with McGann to learn more about why he thinks our noses know more than we realize. Q: Many of us assume our sense of smell is terrible, especially compared with other animals. Where did this idea come from? A: I traced part of this history back to 19th century [anatomist and] anthropologist Paul Broca, who was interested in comparing brains across lots of different animals. Compared to the olfactory bulbs [the first stop for smell signals in the brain], the rest of the human brain is very large. So if you look at whole brains, the bulbs look like these tiny afterthoughts; if you look at a mouse or a rat, the olfactory bulb seems quite big. You can almost forgive Broca for thinking that they didn't matter because they look so small comparatively. Broca believed that a key part of having free will was not being forced to do things by odors. And he thought of smell as this almost dirty, animalistic thing that compelled behaviors—it compelled animals to have sex with each other and things like that. So he put humans in the nonsmeller category—not because they couldn't smell, but because we had free will and could decide how to respond to smells. The idea also got picked up by Sigmund Freud, who then thought of smell as an animalistic thing that had to be left behind as a person grew into a rational adult. So you had in psychology, philosophy, and anthropology all these different pathways leading to presumption that humans didn't have a good sense of smell. © 2017 American Association for the Advancement of Scienc

Keyword: Chemical Senses (Smell & Taste)
Link ID: 23604 - Posted: 05.12.2017

By Kerry Grens In June of 2014, Pablo Meyer went to Rockefeller University in New York City to give a talk about open data. He leads the Translational Systems Biology and Nanobiotechnology group at IBM Research and also guides so-called DREAM challenges, or Dialogue for Reverse Engineering Assessments and Methods. These projects crowdsource the development of algorithms from open data to make predictions for all manner of medical and biological problems—for example, prostate cancer survival or how quickly ALS patients’ symptoms will progress. Andreas Keller, a neuroscientist at Rockefeller, was in the audience that day, and afterward he emailed Meyer with an offer and a request. “He said, ‘We have this data set, and we don’t model,’” recalls Meyer. “‘Do you think you could organize a competition?’” The data set Keller had been building was far from ordinary. It was the largest collection of odor perceptions of its kind—dozens of volunteers, each having made 10 visits to the lab, described 476 different smells using 19 descriptive words (including sweet, urinous, sweaty, and warm), along with the pleasantness and intensity of the scent. Before Keller’s database, the go-to catalog at researchers’ disposal was a list of 10 odor compounds, described by 150 participants using 146 words, which had been developed by pioneering olfaction scientist Andrew Dravnieks more than three decades earlier. Meyer was intrigued, so he asked Keller for the data. Before launching a DREAM challenge, Meyer has to ensure that the raw data provided to competitors do indeed reflect some biological phenomenon. In this case, he needed to be sure that algorithms could determine what a molecule might smell like when only its chemical characteristics were fed in. There were more than 4,800 molecular features for each compound, including structural properties, functional groups, chemical compositions, and the like. “We developed a simple linear model just to see if there’s a signal there,” Meyer says. “We were very, very surprised we got a result. We thought there was a bug.” © 1986-2017 The Scientist

Keyword: Chemical Senses (Smell & Taste); Robotics
Link ID: 23592 - Posted: 05.09.2017

Natalie Jacewicz Sometimes people develop strange eating habits as they age. For example, Amy Hunt, a stay-at-home mom in Austin, Texas, says her grandfather cultivated some unusual taste preferences in his 80s. "I remember teasing him because he literally put ketchup or Tabasco sauce on everything," says Hunt. "When we would tease him, he would shrug his shoulders and just say he liked it." But Hunt's father, a retired registered nurse, had a theory: Her grandfather liked strong flavors because of his old age and its effects on taste. When people think about growing older, they may worry about worsening vision and hearing. But they probably don't think to add taste and smell to the list. "You lose all your senses as you get older, except hopefully not your sense of humor," says Steven Parnes, an ENT-otolaryngologist (ear, nose and throat doctor) working in Albany, N.Y. To understand how aging changes taste, a paean to the young tongue might be appropriate. The average person is born with roughly 9,000 taste buds, according to Parnes. Each taste bud is a bundle of sensory cells, grouped together like the tightly clumped petals of a flower bud. These taste buds cover the tongue and send taste signals to the brain through nerves. Taste buds vary in their sensitivity to different kinds of tastes. Some will be especially good at sensing sweetness, while others will be especially attune to bitter flavors, and so on. © 2017 npr

Keyword: Chemical Senses (Smell & Taste); Development of the Brain
Link ID: 23577 - Posted: 05.05.2017

By Lore Thaler, Liam Norman Echolocation is probably most associated with bats and dolphins. These animals emit bursts of sounds and listen to the echoes that bounce back to detect objects in their environment and to perceive properties of the objects (e.g. location, size, material). Bats, for example, can tell the distance of objects with high precision using the time delay between emission and echo, and are able to determine a difference in distance as small as one centimeter. This is needed for them to be able to catch insects in flight. People, remarkably, can also echolocate. By making mouth clicks, for example, and listening for the returning echoes, they can perceive their surroundings. Humans, of course, cannot hear ultrasound, which may put them at a disadvantage. Nonetheless, some people have trained themselves to an extraordinary level. Daniel Kish, who is blind and is a well-known expert echolocator, is able to ride his bicycle, hike in unfamiliar terrain, and travel in unfamiliar cities on his own. Daniel is the founder and president of World Access for the Blind, a non-profit charity in the US that offers training in echolocation alongside training in other mobility techniques such as the long cane. Since 2011, the scientific interest in human echolocation has gained momentum. For example, technical advances have made it feasible to scan people’s brains while they echolocate. This research has shown that people who are blind and have expertise in echolocation use ‘visual’ parts of their brain to process information from echoes. It has also been found that anyone with normal hearing can learn to use echoes to determine the sizes, locations, or distance of objects or to use it to avoid obstacles during walking. Remarkably, both blind and sighted people can improve their ability to interpret and use sound echoes within a session or two. © 2017 Scientific American

Keyword: Hearing
Link ID: 23570 - Posted: 05.04.2017

By Chris Baraniuk Bat-detecting drones could help us find out what the animals get up to when flying. Ultrasonic detectors on drones in the air and on the water are listening in on bat calls, in the hope of discovering more about the mammals’ lives beyond the reach of ground-based monitoring devices. Drone-builder Tom Moore and bat enthusiast Tom August have developed three different drones to listen for bat calls while patrolling a pre-planned route. Since launching the scheme, known as Project Erebus, in 2014, they have experimented with two flying drones and one motorised boat, all equipped with ultrasonic detectors. The pair’s latest tests have demonstrated the detection capabilities of the two airborne drone models: a quadcopter and a fixed-wing drone. Last month, the quadcopter successfully followed a predetermined course and picked up simulated bat calls produced by an ultrasonic transmitter. The bat signal Moore says one of the major hurdles is detecting the call of bats over the noise of the drones’ propellers, which emit loud ultrasonic frequencies. They overcame this with the quadcopter by dangling the detector underneath the body and rotors of the drone. This is not such a problem for the water-based drone. Last year, Moore and August tested a remote-controlled boat in Oxfordshire, UK, and picked up bat calls thought to belong to common pipistrelle and Daubenton’s bats. The different species often emit different ultrasonic frequencies. © Copyright Reed Business Information Ltd.

Keyword: Hearing; Animal Migration
Link ID: 23524 - Posted: 04.22.2017

By C. CLAIBORNE RAY. The yellow stuff in the outer part of the ear canal, scientifically named cerumen, is only partly a waxy substance, according to the National Institute on Deafness and Other Communication Disorders. The rest of the so-called wax is an accretion of some dust and lots of dead skin cells, which normally collect in the passage as they are shed. The waxy part, which holds the compacted waste together and smooths the way for it to leave the ear, comes from the ceruminous glands, which secrete lipids and other substances. They are specialized sweat glands just under the surface of the skin in the outer part of the canal. Besides lubricating the skin of the canal while keeping it dry, the lipids also help maintain a protective acidic coating, which helps kill bacteria and fungi that can cause infection and irritation. The normal working of muscles in the head, especially those that move the jaw, help guide the wax outward along the ear canal. The ceruminous glands commonly shrink in old age, producing less of the lipids and making it harder for waste to leave the ear. Excess wax buildup can usually be safely softened with warm olive or almond oil or irrigated with warm water, though specialized softening drops are also sold. Take care not to compress the buildup further with cotton swabs or other tools. If it cannot be safely removed, seek medical help. © 2017 The New York Times Company

Keyword: Hearing
Link ID: 23472 - Posted: 04.11.2017

Jon Hamilton The U.S. military is trying to figure out whether certain heavy weapons are putting U.S. troops in danger. The concern centers on the possibility of brain injuries from shoulder-fired weapons like the Carl Gustaf, a recoilless rifle that resembles a bazooka and is powerful enough to blow up a tank. A single round for the Carl Gustaf can weigh nearly 10 pounds. The shell leaves the gun's barrel at more than 500 miles per hour. And as the weapon fires, it directs an explosive burst of hot gases out of the back of the barrel. For safety reasons, troops are trained to take positions to the side of weapons like this. Even so, they get hit by powerful blast waves coming from both the muzzle and breech. "It feels like you get punched in your whole body," is the way one Army gunner described the experience in a military video made in Afghanistan. "The blast bounces off the ground and it overwhelms you." During the wars in Iraq and Afghanistan, the military recognized that the blast from a roadside bomb could injure a service member's brain without leaving a scratch. Hundreds of thousands of U.S. troops sustained this sort of mild traumatic brain injury, which has been linked to long-term problems ranging from memory lapses to post-traumatic stress disorder. Also during those wars, the military began to consider the effects on the brain of repeated blasts from weapons like the Carl Gustaf. And some members of Congress became concerned. © 2017 npr

Keyword: Brain Injury/Concussion; Hearing
Link ID: 23451 - Posted: 04.05.2017

By David Owen When my mother’s mother was in her early twenties, a century ago, a suitor took her duck hunting in a rowboat on a lake near Austin, Texas, where she grew up. He steadied his shotgun by resting the barrel on her right shoulder—she was sitting in the bow—and when he fired he not only missed the duck but also permanently damaged her hearing, especially on that side. The loss became more severe as she got older, and by the time I was in college she was having serious trouble with telephones. (“I’m glad it’s not raining! ” I’d shout, for the third or fourth time, while my roommates snickered.) Her deafness probably contributed to one of her many eccentricities: ending phone conversations by suddenly hanging up. I’m a grandparent myself now, and lots of people I know have hearing problems. A guy I played golf with last year came close to making a hole in one, then complained that no one in our foursome had complimented him on his shot—even though, a moment before, all three of us had complimented him on his shot. (We were walking behind him.) The man who cuts my wife’s hair began wearing two hearing aids recently, to compensate for damage that he attributes to years of exposure to professional-quality blow-dryers. My sister has hearing aids, too. She traces her problem to repeatedly listening at maximum volume to Anne’s Angry and Bitter Breakup Song Playlist, which she created while going through a divorce. My ears ring all the time—a condition called tinnitus. I blame China, because the ringing started, a decade ago, while I was recovering from a monthlong cold that I’d contracted while breathing the filthy air in Beijing, and whose symptoms were made worse by changes in cabin pressure during the long flight home. Tinnitus is almost always accompanied by hearing loss. My internist ordered an MRI, to make sure I didn’t have a brain tumor, and held up a vibrating tuning fork and asked me to tell him when I could no longer hear it. After a while, he leaned forward to make sure the tuning fork was still humming, since he himself could no longer hear it. (We’re about the same age.) © 2017 Condé Nast.

Keyword: Hearing
Link ID: 23434 - Posted: 03.31.2017