Chapter 9. Hearing, Vestibular Perception, Taste, and Smell
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by Hal Hodson IF YOU can hear, you probably take sound for granted. Without thinking, we swing our attention in the direction of a loud or unexpected sound - the honk of a car horn, say. Because deaf people lack access to such potentially life-saving cues, a group of researchers from the Korea Advanced Institute of Science and Technology (KAIST) in Daejeon built a pair of glasses which allows the wearer to "see" when a loud sound is made, and gives an indication of where it came from. An array of seven microphones, mounted on the frame of the glasses, pinpoints the location of such sounds and relays that directional information to the wearer through a set of LEDs embedded inside the frame. The glasses will only flash alerts on sounds louder than a threshold level, which is defined by the wearer. Previous attempts at devices which could alert deaf users to surrounding noises have been ungainly. For example, research in 2003 at the University of California, Berkeley, used a computer monitor to provide users with a visual aid to pinpoint the location of a sound. The Korean team have not beaten this problem quite yet - the prototype requires a user to carry a laptop around in a backpack to process the signal. But lead researcher Yang-Hann Kim stresses that the device is a first iteration that will be miniaturised over the next few years. Richard Ladner at the University of Washington in Seattle questions whether the device would prove beneficial enough to gain acceptance. "Does the benefit of wearing such a device outweigh the inconvenience of having extra technology that is seldom needed?" he asks. © Copyright Reed Business Information Ltd.
Link ID: 17233 - Posted: 09.07.2012
By Susan Milius Caterpillars way too immature for actual sex turn out to detect and take an interest in adult sex pheromones. Caterpillars of the cotton leafworm moth (Spodoptera littoralis) don’t have working sex organs. They’re just long, black-green larvae eating as much as they can before transforming into the completely different body shape and lifestyle of an adult moth. Yet these caterpillars can sense, and appear to like, the adult sex pheromone of their species, an international team reports September 4 in Nature Communications. “This is a funny fact because sex pheromones are supposed to be for sex,” says coauthor Emmanuelle Jacquin-Joly of the French agricultural research agency INRA in Versailles. Adult female moths release puffs of these chemicals, and males catching a whiff — sometimes from considerable distances — sniff their way through the night to the female. Evolution may have repurposed some chemistry in this species, Jacquin-Joly and her colleagues propose. What means “come hither” to adult moths may indicate something quite different, perhaps “here’s food,” to a youngster, she says. She began looking for a cotton leafworm caterpillar pheromone response after another lab found that larval silkworm antennae make the adult-style proteins required to bind molecules of adult sex pheromones from the air and shuttle them to nerve cells. Young silkworms didn’t seem to use the information, but Jacquin-Joly wondered if young cotton leafworms, with a much broader diet, might respond differently. © Society for Science & the Public 2000 - 2012
Tuning a piano also tunes the brain, say researchers who have seen structural changes within the brains of professional piano tuners. Researchers at University College London and Newcastle University found listening to two notes played simultaneously makes the brain adapt. Brain scans revealed highly specific changes in the hippocampus, which governs memory and navigation. These correlated with the number of years tuners had been doing this job. The Wellcome Trust researchers used magnetic resonance imaging to compare the brains of 19 professional piano tuners - who play two notes simultaneously to make them pitch-perfect - and 19 other people. What they saw was highly specific changes in both the grey matter - the nerve cells where information processing takes place - and the white matter - the nerve connections - within the brains of the piano tuners. Investigator Sundeep Teki said: "We already know that musical training can correlate with structural changes, but our group of professionals offered a rare opportunity to examine the ability of the brain to adapt over time to a very specialised form of listening." Other researchers have noted similar hippocampal changes in taxi drivers as they build up detailed information needed to find their way around London's labyrinth of streets. BBC © 2012
By Christie Wilcox Music has a remarkable ability to affect and manipulate how we feel. Simply listening to songs we like stimulates the brain’s reward system, creating feelings of pleasure and comfort. But music goes beyond our hearts to our minds, shaping how we think. Scientific evidence suggests that even a little music training when we’re young can shape how brains develop, improving the ability to differentiate sounds and speech. With education funding constantly on the rocks and tough economic times tightening many parents’ budgets, students often end up with only a few years of music education. Studies to date have focused on neurological benefits of sustained music training, and found many upsides. For example, researchers have found that musicians are better able to process foreign languages because of their ability to hear differences in pitch, and have incredible abilities to detect speech in noise. But what about the kids who only get sparse musical tutelage? Does picking up an instrument for a few years have any benefits? The answer from a study just published in the Journal of Neuroscience is a resounding yes. The team of researchers from Northwestern University’s Auditory Neuroscience Laboratory tested the responses of forty-five adults to different complex sounds ranging in pitch. The adults were grouped based on how much music training they had as children, either having no experience, one to five years of training, or six to eleven years of music instruction. © 2012 Scientific American
by Emily Underwood In the Hans Christian Andersen tale "The Nightingale," a songbird melts an emperor's heart with its singing, but flies away when the ruler forces it to sing duets with a jeweled, mechanical bird that warbles only waltzes. There's a moral here, a new study suggests. Although humans have long attributed musical qualities to birdsong, cold, hard statistics show that's all an illusion. The birds we prize most for their songs sound most like the human voice, says Robert Zatorre, a cognitive neuroscientist at McGill University in Montreal, Canada, who was not involved in the study. The sounds they make have clear tones, repeat similar phrases, and are made of discrete notes. Despite these pleasing attributes, however, it has never been scientifically proven that the notes in birdsong follow the same organizational rules that govern most musical compositions. In fact, says ecologist Marcelo Araya-Salas of New Mexico State University in Las Cruces, author of the new study, no one has ever addressed the question using quantitative methods. Billions of potential notes exist between the low and high notes in an octave. But for reasons that researchers only partially understand—the physiological limits of human hearing, for example, and cultural preferences that have evolved over time—most music is based on variations of only five to 12 notes. A baby grand piano, which has 88 keys, is tuned so that each octave is divided into twelve equal intervals, called half-steps, that form the 12-note chromatic scale underlying most of Western music. The seven-note diatonic scale, "do, re, mi, fa, so, la, ti (do)," is another familiar example, as is the ancient five-note, pentatonic scale used in Greek lyre music and nearly every riff played on the electric guitar. © 2010 American Association for the Advancement of Science
By NATALIE ANGIER Deseada Parejo, a biologist at the Arid Zones Experimental Research Station in Almería, Spain, was studying family dynamics behavior in Eurasian rollers — spectacular jay-size birds with long, slender tails and the Cray-Pas colors of parakeets. On removing one of the nestlings for a standard check of size and weight, she practically jumped at its horror-film response: The tiny chick gaped its mouth wide and vomited up a big dose of sticky orange liquid, enough to fill half a teaspoon. Dr. Parejo touched a second chick, a third, a sixth, and got the same expulsory retort. “I have worked with many other bird species,” she said, “but I never found anything similar to this vomiting behavior before.” Not only that: The fluid had a distinctive, evolving odor. “It’s like orange juice at first,” she said. “Then it begins to smell like insects, like the prey the parents provide.” In the current issue of Biology Letters, Dr. Parejo and her colleagues describe their study of this noteworthy aroma, which they designate the roller nestlings’ “smell of fear.” The researchers said that while the reflux reflex might well serve as a defense mechanism — helping to repel nest predators like snakes and rodents — they were interested in a different question: whether the parents could detect the olfactory cry of alarm, and if so, how they reacted. The answer to the first question was yes. But the parental response to the eau of offspring terror was anything but heroic; instead, it was a bit like those childhood nightmares, where the louder you cry out to Mom and Dad in a crowd, the faster they leave you behind. © 2012 The New York Times Company
By Tina Hesman Saey When a cold takes away a person’s sense of smell, part of the brain that helps link odors with memory, emotion and reward works overtime in preparation for the return of air flow. The way smell rebounds from a period of diminished sensory input distinguishes it from the other senses, researchers at the Northwestern University School of Medicine in Chicago report online August 12 in Nature Neuroscience. Other senses tend to back off when their functions are restricted. When a person wears a patch over one eye, for example, the part of the brain devoted to processing information from that eye weakens while the part linked to the other eye grows stronger. The same is true for hearing and touch, such as when a person goes deaf in one ear or loses a finger. To find out what happens to the olfactory system — the part of the brain that processes scents — when it’s completely odor deprived, Northwestern neuroscientist Joanna Keng Nei Wu and her colleagues set up a scent-free zone in a hospital’s research wing. Volunteers had to give up scented toiletries and spend a week with cotton stuffed up their nostrils to seal their noses off from the outside world. The researchers even took away the volunteers’ toothpaste, forcing them to brush with baking soda instead. Despite the hardships, it wasn’t difficult to find willing volunteers, Wu says. “We had a lot of medical students who wanted us to lock them up in the hospital for a week so they could study.” © Society for Science & the Public 2000 - 2012
Keyword: Chemical Senses (Smell & Taste)
Link ID: 17158 - Posted: 08.14.2012
by Nicholas St. Fleur With their trumpet-like calls, elephants may seem like some of the loudest animals on Earth. But we can't hear most of the sounds they make. The creatures produce low-frequency noises between 1 to 20 Hertz, known as infrasounds, that help them keep in touch over distances as large as 10 kilometers. A new study reveals for the first time how elephants produce these low notes. Scientists first discovered that elephants made infrasounds in the 1980s. The head female in a herd may produce the noises to guide her group's movements, whereas a male who’s in a mating state called musth might use the calls to thwart competition from other males. Mother elephants even rely on infrasounds to keep tabs on a separated calf, exchanging "I'm here" calls with the wayward offspring in a fashion similar to a game of Marco Polo. These noises, which fall below the hearing range for humans, are often accompanied by strong rumbles with slightly higher frequencies that people can hear. By recording the rumbles and then speeding up the playback, the scientists can increase the frequency of the infrasounds, making them audible. Good vibrations. The vocal folds of the excised larynx vibrating according to the myoelastic-aerodynamic method. Researchers have speculated that the noises come from vibrations in the vocal folds of the elephant larynx. This could happen in two ways. In the first, called active muscular contraction (AMC), neural signals cause the muscles in the larynx to contract in a constant rhythm. Cats do this when they purr. The second possibility is known as the myoelastic-aerodynamic (MEAD) method, and it occurs when air flows through the vocal folds causing them to vibrate—this also happens when humans talk. © 2010 American Association for the Advancement of Science
Published by scicurious under Behavioral Neuro Imagine for a minute. You're in a coffeeshop, or a bar, or at a swanky cocktail party (whichever you prefer). There are people around, chatting nearby. But you're speaking to the person directly across from you. Somehow, you can pick their voice out of the chatter and attend to what they are saying, even though the conversations around you might be just as loud or louder (especially in a bar!) than the one you're interested in. Have you ever wondered how you do that? I know I have. It's kind of a mind-boggling problem (and is, in fact, called the Cocktail party problem), trying to separate out speech, and make sense of it, in comparison to all the noise. And it's not just something to think about for us humans. Voice recognition technology and recording wrestles with this all the time: how to pick out the voice from the crowd? As it turns out, it's all about attention, and how that attention can change your brain. The authors of this study were interested in what happens in the brain when someone tries to pick out a single speaker in a room full of people. To look at this, they actually used electrodes implanted subdurally (beneath the tough dura mater on the outside of the brain) in three human patients. Three is a really small number, but they had to use patients who were receiving this electrode implant clinically, in this case for treatment of epilepsy, and who were known to have normal hearing and language skills. Copyright © 2012
by Nicholas St. Fleur A house fly couple settles down on the ceiling of a manure-filled cowshed for a romantic night of courtship and copulation. Unbeknownst to the infatuated insects, their antics have attracted the acute ears of a lurking Natterer's bat. But this eavesdropper is no pervert—he's a predator set on a two-for-one dinner special. As a new study reveals, the hungry bat swoops in on the unsuspecting flies, guided by the sound of their precoital "clicks." Previous studies of freshwater amphipods, water striders, and locusts have shown that mating can make animals more vulnerable to predators, but these studies did not determine why. A team from the Max Planck Institute for Ornithology in Germany, led by the late Björn Siemers, found that the bat-fly interactions in the cowshed provided clues for understanding what tips off a predator to a mating couple. The researchers observed a teenage horror film-like scene as Natterer's bats (Myotis nattereri)preyed on mating house flies (Musca domestica). Bats find prey primarily through two methods: echolocation and passive acoustics. For most bats, echolocation is the go-to tracking tool. They send out a series of high frequency calls and listen for the echoes produced when the waves hit something. The researchers found that by using echolocation, bats could easily find and catch house flies midflight, yet they had difficulty hunting stationary house flies. © 2010 American Association for the Advancement of Science
by Gisela Telis During mating season, a moss needs a little help from its friends—and it uses smell to recruit them. A new study has found that mosses, which were long thought to require only water or wind to reproduce, release an aroma that entices tiny animals such as mites and little bugs called springtails to help fertilize the plants. The discovery challenges current ideas about plant evolution, but experts say it raises more questions than it answers. For mosses, sex can be tricky. They can reproduce asexually, or they can develop male and female sex organs and wait for their fragile sperm to travel from one to the other. If the latter occurs, they rely on the elements—wind or splashing rain—to help with transport. In 2006, researchers discovered a third means of delivery. They found that tiny arthropods, a group of creepy-crawlies that includes mites and springtails, seemed to help disperse moss sperm. But the study didn't pinpoint how they did it or whether this kind of fertilization was critical to the moss life cycle. In hopes of answering those lingering questions, biologist Sarah Eppley of Portland State University in Oregon and colleagues gathered and grew moss samples from local forests and tested reproductive outcomes with and without rain and springtails. They found that water alone and springtails alone were equally effective at fertilizing mosses, but putting the two together made the mosses more than twice as successful at reproducing. © 2010 American Association for the Advancement of Science
By Victoria Gill BBC Nature Seabirds are able to pick out their relatives from smell alone, according to scientists. In a "recognition test", European storm petrels chose to avoid the scent of a relative in favour of approaching the smell of an unrelated bird. The researchers think this behaviour prevents the birds from "accidentally inbreeding". The study is the first evidence that birds are able to sniff out a suitable mate. It is published in the journal Animal Behaviour. Lead researcher Francesco Bonadonna, from the Centre of Functional and Evolutionary Ecology in Montpellier, France, told BBC Nature that the birds used smell to recognise and communicate their "genetic compatibility". Sniffing out a genetically suitable mate is a well-known phenomenon in mammals. But until recently, scientists thought that birds relied on vision and sound when choosing a partner. According to Dr Bonadonna, the fact that they use odours explains how these birds manage to return to their family colony to breed and avoid mating with a relative. European storm petrels remain in the colony they are born in throughout their life, so this site is also home to several of their family members. BBC © 2012
By WILLIAM J. BROAD Scientists have long known that man-made, underwater noises — from engines, sonars, weapons testing, and such industrial tools as air guns used in oil and gas exploration — are deafening whales and other sea mammals. The Navy estimates that loud booms from just its underwater listening devices, mainly sonar, result in temporary or permanent hearing loss for more than a quarter-million sea creatures every year, a number that is rising. Now, scientists have discovered that whales can decrease the sensitivity of their hearing to protect their ears from loud noise. Humans tend to do this with index fingers; scientists haven’t pinpointed how whales do it, but they have seen the first evidence of the behavior. “It’s equivalent to plugging your ears when a jet flies over,” said Paul E. Nachtigall, a marine biologist at the University of Hawaii who led the discovery team. “It’s like a volume control.” The finding, while preliminary, is already raising hopes for the development of warning signals that would alert whales, dolphins and other sea mammals to auditory danger. Peter Madsen, a professor of marine biology at Aarhus University in Denmark, said he applauded the Hawaiian team for its “elegant study” and the promise of innovative ways of “getting at some of the noise problems.” But he cautioned against letting the discovery slow global efforts to reduce the oceanic roar, which would aid the beleaguered sea mammals more directly. © 2012 The New York Times Company
People who are born deaf process the sense of touch differently than people who are born with normal hearing, according to research funding by the National Institutes of Health. The finding reveals how the early loss of a sense — in this case hearing — affects brain development. It adds to a growing list of discoveries that confirm the impact of experiences and outside influences in molding the developing brain. The study is published in the July 11 online issue of The Journal of Neuroscience. The researchers, Christina M. Karns, Ph.D., a postdoctoral research associate in the Brain Development Lab at the University of Oregon, Eugene, and her colleagues, show that deaf people use the auditory cortex to process touch stimuli and visual stimuli to a much greater degree than occurs in hearing people. The finding suggests that since the developing auditory cortex of profoundly deaf people is not exposed to sound stimuli, it adapts and takes on additional sensory processing tasks. "This research shows how the brain is capable of rewiring in dramatic ways," said James F. Battey, Jr., M.D., Ph.D., director of the NIDCD. "This will be of great interest to other researchers who are studying multisensory processing in the brain." Previous research, including studies performed by the lab director, Helen Neville Ph.D., has shown that people who are born deaf are better at processing peripheral vision and motion. Deaf people may process vision using many different brain regions, especially auditory areas, including the primary auditory cortex. However, no one has tackled whether vision and touch together are processed differently in deaf people, primarily because in experimental settings, it is more difficult to produce the kind of precise tactile stimuli needed to answer this question.
by Elizabeth Preston It's 20 million years ago in the forests of Argentina, and Homunculus patagonicus is on the move. The monkey travels quickly, swinging between tree branches as it goes. Scientists have a good idea of how Homunculus got around thanks to a new fossil analysis of its ear canals and those of 15 other ancient primates. These previously hidden passages reveal some surprises about the locomotion of extinct primates—including hints that our own ancestors spent their lives moving at a higher velocity than today's apes. Wherever skeletons of ancient primates exist, anthropologists have minutely analyzed arm, leg, and foot bones to learn about the animals' locomotion. Some of these primates seem to have bodies built for leaping. Others look like they moved more deliberately. But in species such as H. patagonicus, there's hardly anything to go on aside from skulls. That's where the inner ear canals come in. "The semicircular canals function essentially as angular accelerometers for the head," helping an animal keep its balance while its head jerks around, says Timothy Ryan, an anthropologist at Pennsylvania State University, University Park. In the new study, he and colleagues used computed tomography scans to peer inside the skulls of 16 extinct primates, spanning 35 million years of evolution, and reconstruct the architecture of their inner ears. © 2010 American Association for the Advancement of Science
Children exposed to HIV in the womb may be more likely to experience hearing loss by age 16 than are their unexposed peers, according to scientists in a National Institutes of Health research network. The researchers estimated that hearing loss affects 9 to 15 percent of HIV-infected children and 5 to 8 percent of children who did not have HIV at birth but whose mothers had HIV infection during pregnancy. Study participants ranged from 7 to 16 years old. The researchers defined hearing loss as the level at which sounds could be detected, when averaged over four frequencies important for speech understanding (500, 1000, 2000, and 4000 Hertz), that was 20 decibels or higher than the normal hearing level for adolescents or young adults in either ear. “Children exposed to HIV before birth are at higher risk for hearing difficulty, and it's important for them—and the health providers who care for them—to be aware of this,” said George K. Siberry, M.D., of the Pediatric, Adolescent, and Maternal AIDS Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the NIH institute that leads the research network. Compared to national averages for other children their age, children with HIV infection were about 200 to 300 percent more likely to have a hearing loss. Children whose mothers had HIV during pregnancy but who themselves were born without HIV were 20 percent more likely than to have hearing loss. The study was published online in The Pediatric Infectious Disease Journal.
By Scicurious Before I started college, there was a sudden rage amongst my male friends. A rage for one specific thing. Not phones or computers or cars or clothes. Nope. It was for a guitar. Most of the guys I knew, in the year or two before college, suddenly became obsessed with the guitar, picking out melodies, trying to match still changing warbling voices to a hopefully tuned instrument. I couldn’t figure it out. What was up with the guitar obsession?! Some of these people were people who never had displayed a musical bent their entire lives, and here they were, sitting experimentally on the benches outside my school with guitars in hand. Finally, I asked my brother (who also, of course, had taken up the guitar), why every guy seemed to want to play the guitar. Why not the cello or the piano or the trombone or the kazoo? My brother rolled his eyes at my denseness. “For the GIRLS, of course” (And yes, specifically, they ALL wanted to play this song. I would hypothesize that about 80% of the men I know can pick out this song on the guitar. Considering that a substantial portion of the female populace does indeed have brown eyes, I realize the efficiency of this method, but for those of us with non-brown eyes, this song is IRRITATING BEYOND BELIEF. This has been a public service announcement.) © 2012 Scientific American
By Susan Milius ALBUQUERQUE — Unbeknownst to humans, peacocks may be having infrasonic conversations. New recordings reveal that males showing off their feathers make deep rumbling sounds that are too low pitched for humans to hear. Other peacocks hear it though, Angela Freeman reported June 13 at the annual meeting of the Animal Behavior Society. When she played recordings of the newly discovered sound to peafowl, females looked alert and males were likely to shriek out a (human-audible) call. Peacocks are thus the first birds known to make and perceive noises below human hearing, Freeman said. ”Really exciting,” said Roslyn Dakin of Queen’s University in Kingston, Canada, who studies the visual allure of peacock courtship. If peacocks can rumble, she suspects that other birds may be able to, too. “I don’t think this is a weird case,” she said. Such infrasound, or noise below 20 hertz, extends below the limit of human hearing. Biologists watched creatures such as elephants for centuries before recording technology uncovered the infrasound side of those animal conversations. But making infrasound doesn’t always mean communicating with it. Recordings have picked up infrasound from another bird, the capercaillie, but playing back the sounds to those birds has so far revealed no sign that they hear or care about their own infrasound. Freeman, an animal behaviorist at the University of Manitoba, was inspired to make detailed recordings of male peacocks by her coauthor’s impression that their fanned-out feather display curved slightly forward like a shallow satellite dish. © Society for Science & the Public 2000 - 2012
By Janet Raloff By baffling the brain, saccharin and other sugar-free sweeteners — key weapons in the war on obesity — may paradoxically foster overeating. At some level, the brain can sense a difference between sugar and no-calorie sweeteners, several studies have demonstrated. Using brain imaging, San Diego researchers now show that the brain processes sweet flavors differently depending on whether a person regularly consumes diet soft drinks. “This idea that there could be fundamental differences in how people respond to sweet tastes based on their experience with diet sodas is not something that has gotten much attention,” says Susan Swithers of Purdue University in West Lafayette, Ind. A key finding, she says: Brains of diet soda drinkers “don’t differentiate very well between sucrose and saccharin.” Erin Green and Claire Murphy of the University of California, San Diego and San Diego State University recruited 24 healthy young adults for a battery of brain imaging tests. Half reported regularly drinking sugar-free beverages, usually at least once a day. The rest seldom if ever consumed such drinks. While the brain scans were underway, the researchers pumped small amounts of saccharin- or sugar-sweetened water in random order into each recruit’s mouth as the volunteer rated the tastes. Both the diet soda drinkers and the nondrinkers rated each sweetener about equally pleasant and intense, Green and Murphy report in an upcoming Physiology & Behavior. But which brain regions lit up while making those judgments differed sharply based on who regularly consumed diet drinks. © Society for Science & the Public 2000 - 2012
By Ferris Jabr The human body is a tireless gardener, growing new cells throughout life in many organs—in the skin, blood, bones and intestines. Until the 1980s most scientists thought that brain cells were the exception: the neurons you are born with are the neurons you have for life. In the past three decades, however, researchers have discovered hints that the human brain produces new neurons after birth in two places: the hippocampus—a region important for memory—and the walls of fluid-filled cavities called ventricles, from which stem cells migrate to the olfactory bulb, a knob of brain tissue behind the eyes that processes smell. Studies have clearly demonstrated that such migration happens in mice long after birth and that human infants generate new neurons. But the evidence that similar neurogenesis persists in the adult human brain is mixed and highly contested. A new study relying on a unique form of carbon dating suggests that neurons born during adulthood rarely if ever weave themselves into the olfactory bulb's circuitry. In other words, people—unlike other mammals—do not replenish their olfactory bulb neurons, which might be explained by how little most of us rely on our sense of smell. Although the new research casts doubt on the renewal of olfactory bulb neurons in the adult human brain, many neuroscientists are far from ready to end the debate. In preparation for the new study, Olaf Bergmann and Jonas Frisén of the Karolinska Institute in Stockholm and their colleagues acquired 14 frozen olfactory bulbs from autopsies performed between 2005 and 2011 at the institute's Department of Forensic Medicine. To determine whether the neurons were younger than the people they came from—which would mean the cells were generated after birth—the researchers needed to isolate the cells' DNA. © 2012 Scientific American,