Chapter 9. Hearing, Vestibular Perception, Taste, and Smell
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
By Susan Milius In nighttime flying duels, Mexican free-tailed bats make short, wavering sirenlike waaoo-waaoo sounds that jam each other’s sonar. These “amazing aerial battles” mark the first examples of echolocating animals routinely sabotaging the sonar signals of their own kind, says Aaron Corcoran of Wake Forest University in Winston-Salem, N.C. Many bats, like dolphins, several cave-dwelling birds and some other animals, locate prey and landscape features by pinging out sounds and listening for echoes. Some prey, such as tiger moths, detect an incoming attack and make frenzied noises that can jam bat echolocation, Corcoran and his colleagues showed in 2009 (SN: 1/31/09, p. 10). And hawkmoths under attack make squeaks with their genitals in what also may be defensive jamming (SN Online: 7/3/13). But Corcoran didn’t expect bat-on-bat ultrasonic warfare. He was studying moths dodging bats in Arizona’s Chiricahua Mountains when his equipment picked up a feeding buzz high in the night sky. A free-tailed bat was sending faster and faster echolocation calls to refine the target position during the final second of an attack. (Bats, the only mammals known with superfast muscles, can emit more than 150 sounds a second.) Then another free-tailed bat gave a slip-sliding call. Corcoran, in a grad student frenzy of seeing his thesis topic as relevant to everything, thought the call would be a fine way to jam a buzz. “Then I totally told myself that’s impossible — that’s too good to be true.” Five years later he concluded he wasn’t just hearing things. He and William Conner, also of Wake Forest, report in the Nov. 7 Science that the up-and-down call can cut capture success by about 70 percent. Using multiple microphones, he found that one bat jams another, swoops toward the moth and gets jammed itself. © Society for Science & the Public 2000 - 201
Link ID: 20435 - Posted: 12.20.2014
By Will Dunham WASHINGTON (Reuters) - You might want to be careful about who you call a birdbrain. Some of our feathered friends exhibit powers of perception that put humans to shame. Scientists said on Thursday that little songbirds known as golden-winged warblers fled their nesting grounds in Tennessee up to two days before the arrival of a fierce storm system that unleashed 84 tornadoes in southern U.S. states in April. The researchers said the birds were apparently alerted to the danger by sounds at frequencies below the range of human hearing. The storm killed 35 people, wrecked many homes, toppled trees and tossed vehicles around like toys, but the warblers were already long gone, flying up to 930 miles (1,500 km) to avoid the storm and reaching points as far away as Florida and Cuba, the researchers said. Local weather conditions were normal when the birds took flight from their breeding ground in the Cumberland Mountains of eastern Tennessee, with no significant changes in factors like barometric pressure, temperature or wind speeds. And the storm, already spawning tornadoes, was still hundreds of miles away. "This suggests that these birds can detect severe weather at great distances," said wildlife biologist David Andersen of the U.S. Geological Survey and the University of Minnesota, one of the researchers in the study published in the journal Current Biology. "We hypothesize that the birds were detecting infrasound from tornadoes that were already occurring when the storm was still quite distant from our study site," Andersen added.
By Sandhya Sekar A well-fed female mantis is irresistible to a male. She’s chock-full of eggs and draws him in by producing high levels of pheromones. Now, a new study reveals that starving females can deceive males by enticing them to their doom. Researchers have found that female false garden mantises (Pseudomantis albofimbriata, pictured) that were fed just a quarter of what others got actually produced more pheromones than well-fed females—and attracted almost twice the number of males. This is despite the fact that the number of eggs in the starved females was less than 10, compared with more than 60 eggs in well-fed females. The finding, reported online today in the Proceedings of the Royal Society B, is the first experimental demonstration of sexual deception using false chemical signals in any animal. The starving females seem to be treating the males as easy prey to gain nutritional benefits and potentially produce more eggs. © 2014 American Association for the Advancement of Science
By Bruce Bower In the movie Roxanne, Steve Martin plays a lovesick guy who mocks his own huge schnoz by declaring: “It’s not the size of a nose that’s important. It’s what’s in it that matters.” Scientists demonstrated the surprising truth behind that joke this year: People can whiff an average of more than 1 trillion different odors, regardless of nose size (SN: 4/19/14, p. 6). No one had systematically probed how many scents people can actually tell apart. So a team led by Leslie Vosshall of Rockefeller University in New York City asked 26 men and women to discriminate between pairs of scents created from mixes of 128 odor molecules. Volunteers easily discriminated between smells that shared as much as 51 percent of their odor molecules. Errors gradually rose as pairs of scents became chemically more alike. Vosshall’s group calculated that an average participant could tell apart a minimum of more than 1 trillion smells made up of different combinations of 30 odor molecules. Really good smellers could have detected way more than 1 trillion odor mixtures, the scientists said. Smell lags behind sight and hearing as a sense that people need to find food, avoid dangers and otherwise succeed at surviving. Still, detecting the faint odor of spoiled food and other olfactory feats must have contributed to the success of Homo sapiens over the last 200,000 years. Perhaps many animals can whiff the difference between a trillion or more smells. For now, odor-detection studies modeled on Vosshall’s approach have been conducted only with humans. © Society for Science & the Public 2000 - 2014.
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20417 - Posted: 12.16.2014
By recording from the brains of bats as they flew and landed, scientists have found that the animals have a "neural compass" - allowing them to keep track of exactly where and even which way up they are. These head-direction cells track bats in three dimensions as they manoeuvre. The researchers think a similar 3D internal navigation system is likely to be found throughout the animal kingdom. The findings are published in the journal Nature. Lead researcher Arseny Finkelstein, from the Weizmann Institute of Science in Rehovot, Israel, explained that this was the first time measurements had been taken from animals as they had flown around a space in any direction and even carried out their acrobatic upside-down landings. "We're the only lab currently able to conduct wireless recordings in flying animals," he told BBC News. "A tiny device attached to the bats allows us to monitor the activity of single neurons while the animal is freely moving." Decades of study of the brain's internal navigation system garnered three renowned neuroscientists this year's Nobel Prize for physiology and medicine. The research, primarily in rats, revealed how animals had "place" and "grid" cells - essentially building a map in the brain and coding for where on that map an animal was at any time. Mr Finkelstein and his colleagues' work in bats has revealed that their brains also have "pitch" and "roll" cells. These tell the animal whether it is pointing upwards or downwards and whether its head is tilted one way or the other. BBC © 2014
By Beth Winegarner When Beth Wankel’s son, Bowie, was a baby, he seemed pretty typical. But his “terrible twos” were more than terrible: In preschool, he would hit and push his classmates to a degree that worried his parents and teachers. As Bowie got a little older, he was able tell his mom why he was so combative. “He would say things like, 'I thought they were going to step on me or push me,’” Wankel said. “He was overly uncomfortable going into smaller spaces; it was just too much for him.” Among other things, he refused to enter the school bathroom if another student was inside. When Bowie was 3, he was formally evaluated by his preschool teachers. They said he appeared to be having trouble processing sensory input, especially when it came to figuring out where his body is in relation to other people and objects. He’s also very sensitive to touch and to the textures of certain foods, said Wankel, who lives with her family in San Francisco. Bowie has a form of what’s known as sensory processing disorder. As the name suggests, children and adults with the disorder have trouble filtering sights, smells, sounds and more from the world around them. While so-called neurotypicals can usually ignore background noise, clothing tags or cluttered visual environments, people with SPD notice all of those and more — and quickly become overwhelmed by the effort. Rachel Schneider, a mental-health expert and a blogger for adults with SPD, describes it as a “neurological traffic jam” or “a soundboard, except the sound technician is terrible at his job.”
By Joyce Cohen Like many people, George Rue loved music. He played guitar in a band. He attended concerts often. In his late 20s, he started feeling a dull ache in his ears after musical events. After a blues concert almost nine years ago, “I left with terrible ear pain and ringing, and my life changed forever,” said Mr. Rue, 45, of Waterford, Conn. He perceived all but the mildest sounds as not just loud, but painful. It hurt to hear. Now, he has constant, burning pain in his ears, along with ringing, or tinnitus, so loud it’s “like a laser beam cutting a sheet of steel.” Everyday noise, like a humming refrigerator, adds a feeling of “needles shooting into my ears,” said Mr. Rue, who avoids social situations and was interviewed by email because talking by phone causes pain. Mr. Rue was given a diagnosis of hyperacusis, a nonspecific term that has assorted definitions, including “sound sensitivity,” “decreased sound tolerance,” and “a loudness tolerance problem.” But hyperacusis sometimes comes with ear pain, too, a poorly understood medical condition that is beginning to receive more serious attention. “This is clearly an emerging field,” said Richard Salvi of the Department of Communicative Disorders and Sciences at the University at Buffalo and a scientific adviser to Hyperacusis Research, a nonprofit group that funds research on the condition. “Further work is required to understand the symptoms, etiology and underlying neural mechanisms.” Loud noises, even when they aren’t painful, can damage both the sensory cells and sensory nerve fibers of the inner ear over time, causing hearing impairment, said M. Charles Liberman, a professor of otology at Harvard Medical School, who heads a hearing research lab at the Massachusetts Eye and Ear Infirmary. And for some people who are susceptible, possibly because of some combination of genes that gives them “tender” ears, noise sets in motion “an anomalous response,” he said. © 2014 The New York Times Company
Link ID: 20381 - Posted: 12.02.2014
By Sandra G. Boodman ‘That’s it — I’m done,” Rachel Miller proclaimed, the sting of the neurologist’s judgment fresh as she recounted the just-concluded appointment to her husband. Whatever was wrong with her, Miller decided after that 2009 encounter, she was not willing to risk additional humiliation by seeing another doctor who might dismiss her problems as psychosomatic. The Baltimore marketing executive had spent the previous two years trying to figure out what was causing her bizarre symptoms, some of which she knew made her sound delusional. Her eyes felt “weird,” although her vision was 20/20. Normal sounds seemed hugely amplified: at night when she lay in bed, her breathing and heartbeat were deafening. Water pounding on her back in the shower sounded like a roar. She was plagued by dizziness. “I had started to feel like a person in one of those stories where someone has been committed to a mental hospital by mistake or malice and they desperately try to appear sane,” recalled Miller, now 53. She began to wonder if she really was crazy; numerous tests had ruled out a host of possible causes, including a brain tumor. Continuing to look for answers seemed futile, since all the doctors she had seen had failed to come up with anything conclusive. “My attitude was: If it’s something progressive like MS [multiple sclerosis] or ALS [amyotrophic lateral sclerosis], it’ll get bad enough that someone will eventually figure it out.” Figuring it out would take nearly three more years and was partly the result of an oddity that Miller mentioned to another neurologist, after she lifted her moratorium on seeing doctors.
Link ID: 20353 - Posted: 11.25.2014
By Jyoti Madhusoodanan Eurasian jays are tricky thieves. They eavesdrop on the noises that other birds make while hiding food in order to steal the stash later, new research shows. Scientists trying to figure out if the jays (Garrulus glandarius) could remember sounds and make use of the information placed trays of two materials—either sand or gravel—in a spot hidden from a listening jay’s view. Other avian participants of the same species, which were given a nut, cached the treat in one of the two trays. Fifteen minutes later, the listening bird was permitted to hunt up the stash (video). When food lay buried in a less noisy material such as sand, jays searched randomly. But if they heard gravel being tossed around as treats were hidden, they headed to the pebbles to pilfer the goods. Previous studies have shown that jays—like crows, ravens, and other bird burglars that belong to the corvid family—can remember where they saw food being hidden and return to the spot to look for the cache. But these new results, published in Animal Cognition this month, provide the first evidence that these corvids can also recollect sounds to locate and steal stashes of food. In their forest homes, where birds are heard more often than they are seen, this sneaky strategy might give eavesdropping jays a better chance at finding hidden feasts.
Link ID: 20339 - Posted: 11.21.2014
By Abby Phillip You know the ones: They seem to be swaying to their own music or clapping along to a beat only they can hear. You may even think that describes you. The majority of humans, however, do this very well. We clap, dance, march in unison with few problems; that ability is part of what sets us apart from other animals. But it is true that rhythm — specifically, coordinating your movement with something you hear — doesn't come naturally to some people. Those people represent a very small sliver of the population and have a real disorder called "beat deafness." Unfortunately, your difficulty dancing or keeping time in band class probably doesn't quite qualify. A new study by McGill University researchers looked more closely at what might be going on with "beat deaf" individuals, and the findings may shed light on why some people seem to be rhythm masters while others struggle. Truly beat deaf people have a very difficult time clapping or tapping to an auditory beat or swaying to one. It's a problem that is far more severe than a lack of coordination. And it isn't attributable to motor skills, hearing problems or even a person's inability to create a regular rhythm. Illustrating how rare the disorder really is, McGill scientists received hundreds of inquiries from people who thought they were beat deaf, but only two qualified as having truly severe problems.
Link ID: 20304 - Posted: 11.13.2014
By James Gallagher Health editor, BBC News website The brain has specialist neurons for each of the five taste categories - salty, bitter, sour, sweet and umami - US scientists have discovered. The study, published in the journal Nature, should settle years of debate on how the brain perceives taste. The Columbia University team showed the separate taste sensors on the tongue had a matching partner in the brain. The scientists hope the findings could be used to help reverse the loss of taste sensation in the elderly. It is a myth that you taste sweet only on the tip of the tongue. Each of the roughly 8,000 taste buds scattered over the tongue is capable of sensing the full suite of tastes. But specialised cells within the taste bud are tuned to either salty, bitter, sour, sweet or umami tastes. When they detect the signal, a message is sent to the brain. Although how the brain deals with the information has been up for discussion. A team at Columbia University engineered mice so that their taste neurons would fluoresce when they were activated. They then trained their endoscopes on the neurons deep at their base of the brain. The animals were fed chemicals to trigger either a salty, bitter, sour, sweet or umami response on the tongue and the researchers monitored the change in the brain. They found a "hard wired" connection between tongue and brain. Prof Charles Zuker told the BBC News website: "The cells were beautifully tuned to discrete individual taste qualities, so you have a very nice match between the nature of the cells in your tongue and the quality they represent [in the brain]." It scotches the alternative idea that brain cells respond to multiple tastes. BBC © 2014
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20295 - Posted: 11.10.2014
Carl Zimmer Milk is not just food. The more closely scientists examine it, the more complexity they find. Along with nutrients like protein and calcium, milk contains immune factors that protect infants from disease. It hosts a menagerie of microbes, too, some of which may colonize the guts of babies and help them digest food. Milk even contains a special sugar that can fertilize that microbial garden. Now, it turns out, milk also contains messages. A new study of monkeys, published in the journal Behavioral Ecology, demonstrates that a hormone present in milk, cortisol, can have profound effects on how babies develop. Infant monkeys rely on cortisol to detect the condition of their mothers, the authors suggest, then adjust their growth and even shift their temperaments. Jeffrey French, a neuroendocrinologist at the University of Nebraska at Omaha who was not involved in the study, praised its “remarkable sophistication” and said that it helped to change how we think about breast milk. “Milk serves almost like a pheromone, a chemical signal sent from one individual to another,” he said. Katie Hinde, a behavioral biologist at Harvard and lead author on the new study, and her colleagues studied 108 rhesus macaque mothers nursing infants at the California National Primate Research Center. The researchers collected samples of milk, measuring how much energy each provided and the cortisol it contained. Dr. Hinde and her colleagues also measured how much weight each nursing monkey gained and tracked its behavior. Cortisol serves many functions in mammals, but it is best known as a stress hormone. When cortisol courses through our bodies, it prepares us to handle alarming or fearful situations, increasing the brain’s consumption of glucose and suppressing the digestive system. © 2014 The New York Times Company
by Penny Sarchet It's frustrating when your smartphone loses its signal in the middle of a call or when downloading a webpage. But for bats, a sudden loss of its sonar signal means missing an insect meal in mid-flight. Now there's evidence to suggest that bats are sneakily using sonar jamming techniques to make their fellow hunters miss their tasty targets. Like other bats, the Mexican free-tailed bat uses echolocation to pinpoint prey insects in the dark. But when many bats hunt in the same space, they can interfere with each other's echoes, making detection more difficult. Jamming happens when a sound disrupts a bat's ability to extract location information from the echoes returning from its prey, explains Aaron Corcoran of Johns Hopkins University in Baltimore, Maryland. Previous research has shown that Mexican free-tailed bats can get around this jamming by switching to higher pitches. Using different sound frequencies to map the hunting grounds around them allows many bats to hunt in the same space. In these studies, jamming of each other's signals was seemingly inadvertent – a simple consequence of two bats attempting to echolocate in close proximity. But Corcoran has found evidence of sneakier goings-on. Corcoran has found a second type of sonar jamming in these bats – intentional sabotage of a fellow bat. "In this study, the jamming is on purpose and the jamming signal has been designed by evolution to maximally disrupt the other bat's echolocation," he says. © Copyright Reed Business Information Ltd.
Link ID: 20288 - Posted: 11.08.2014
by Catherine Brahic Once described as the finest sound in nature, the song of the North American hermit thrush has long captivated the human ear. For centuries, birdwatchers have compared it to human music – and it turns out they were on to something. The bird's song is beautifully described by the same maths that underlies human harmonies. To our ears, two notes usually sound harmonious together if they follow a set mathematical relationship. An octave is a doubling of frequencies. Tripling the frequency of sound produces a perfect fifth, quadrupling is yet another octave, and quintupling produces a perfect third. These relationships define the most common major chords – the ones that, across human cultures, we tend to find most pleasant to listen to. Early studies sought to determine whether these mathematical relationships also governed the notes in bird song. Studies in the white-throated sparrow and the northern nightingale-wren failed to find the same musical intervals as those used in human music, and deemed birdsong to be something different entirely. Making tweet music The song of the hermit thrush challenges that conclusion. Tecumseh Fitch of the University of Vienna in Austria and colleagues analysed recordings taken in the wild of 70 full songs from this species. They isolated the frequencies corresponding to each note, and calculated the relationships between pitches appearing in each song. Lo and behold, the vast majority of songs used notes that fitted the same simple mathematical ratios as human harmony. What's more, Fitch says the thrush can produce other notes - meaning it must choose to use these harmonic chords. © Copyright Reed Business Information Ltd.
by Aviva Rutkin IF DINNER is missing some zing, a spoon studded with electrodes could help. It creates tastes on your tongue with a pulse of electricity. The utensil may add some extra flavour for people who shouldn't eat certain foods. Different frequencies and magnitudes of current through the electrodes can create the impression of saltiness, sourness or bitterness. The spoon was developed by Nimesha Ranasinghe at the New York University Abu Dhabi in the United Arab Emirates and his team, who have also developed a water bottle with similar hardware on the mouthpiece. Both devices use various coloured lights, like blue for salty, in an attempt to augment the perceived intensity of the flavour. "Taste is not only taste. It's a multisensory sensation, so we need smell, colour, previous experiences, texture," says Ranasinghe. "I am trying to integrate different aspects of these sensations." By boosting the flavour of plain foods, he says a tool like this could be useful for people with diabetes or heart issues who have been ordered to cut down on salt and sugar. To see how well the electric utensils could fool diners, 30 people tried them out in a taste test with plain water and porridge. The spoon and bottle were judged 40 to 83 per cent successful at recreating the tastes, depending on which one they were aiming for. Bitter was the hardest sensation to get right. Some testers also said they were distracted by the metallic taste of the electrodes – a pitfall the researchers will work on next. © Copyright Reed Business Information Ltd.
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20268 - Posted: 11.03.2014
By BENEDICT CAREY A Polish man who was paralyzed from the chest down after a knife attack several years ago is now able to get around using a walker and has recovered some sensation in his legs after receiving a novel nerve-regeneration treatment, according to a new report that has generated both hope and controversy. The case, first reported widely by the BBC and other British news outlets, has stirred as much excitement on the Internet as it has extreme caution among many experts. “It is premature at best, and at worst inappropriate, to draw any conclusions from a single patient,” said Dr. Mark H. Tuszynski, director of the translational neuroscience unit at the medical school of the University of California, San Diego. That patient — identified as Darek Fidyka, 40 — is the first to recover feeling and mobility after getting the novel therapy, which involves injections of cultured cells at the site of the injury and tissue grafts, the report said. The techniques have shown some promise in animal studies. But the medical team, led by Polish and English doctors, also emphasized that the results would “have to be confirmed in a larger group of patients sustaining similar types of spinal injury” before the treatment could be considered truly effective. The case report was published in the journal Cell Transplantation. The history of spinal injury treatment is studded with false hope and miracle recoveries that could never be replicated, experts said. In previous studies, scientists experimented with some of the same methods used on Mr. Fidyka, with disappointing results. © 2014 The New York Times Company
|By Steve Mirsky People have been leaving messages on bathroom walls for thousands of years. Just google “ancient Roman bathroom graffiti.” But we’re not the only ones to use latrines for information exchange—as two German researchers have confirmed after hundreds of hours watching lemurs pee and poop. For science. Primatologists Iris Dröscher and Peter Kappeler concentrated on seven sets of pair-bonded members of a species called white-footed sportive lemurs, at a nature reserve in southern Madagascar. Their report is in the journal Behavioral Ecology and Sociobiology. [Iris Dröscher & Peter M. Kappeler Maintenance of familiarity and social bonding via communal latrine use in a solitary primate (Lepilemur leucopus)] Many animals use the same spots repeatedly to do their business, primates in particular. For these lemurs, a specific tree becomes the urine and feces focal point. And because chemical compounds in their waste transmit information, the so-called latrine tree becomes like a bulletin board to post messages for the rest of the community. Based on their 1,097 hours of observations, the researchers conclude that urine and glandular secretions left on the tree trunk are the primary message vehicles. Feces mostly just collects on the ground. Some urine telegrams are probably signals from a particular lemur to the neighbors that he or she is around. But male lemurs upped their latrine visits when potential competitors for females came into their home area. So the frequent chemical messages left on the tree probably say in that case, “Buzz off, buddy, she’s with me.” In lemur. © 2014 Scientific American,
By ALEX STONE Smell is one of the oldest human faculties, yet it was one of the last to be understood by scientists. It was not until the early 1990s that biologists first described the inner workings of olfactory receptors — the chemical sensors in our noses — in a discovery that won a Nobel Prize. Since then, the plot has thickened. Over the last decade or so, scientists have discovered that odor receptors are not solely confined to the nose, but found throughout body — in the liver, the heart, the kidneys and even sperm — where they play a pivotal role in a host of physiological functions. Now, a team of biologists at Ruhr University Bochum in Germany has found that our skin is bristling with olfactory receptors. “More than 15 of the olfactory receptors that exist in the nose are also found in human skin cells,” said the lead researcher, Dr. Hanns Hatt. Not only that, but exposing one of these receptors (colorfully named OR2AT4) to a synthetic sandalwood odor known as Sandalore sets off a cascade of molecular signals that appears to induce healing in injured tissue. In a series of human tests, skin abrasions healed 30 percent faster in the presence of Sandalore, a finding the scientists think could lead to cosmetic products for aging skin and to new treatments to promote recovery after physical trauma. The presence of scent receptors outside the nose may seem odd at first, but as Dr. Hatt and others have observed, odor receptors are among the most evolutionarily ancient chemical sensors in the body, capable of detecting a multitude of compounds, not solely those drifting through the air. “If you think of olfactory receptors as specialized chemical detectors, instead of as receptors in your nose that detect smell, then it makes a lot of sense for them to be in other places,” said Jennifer Pluznick, an assistant professor of physiology at Johns Hopkins University who in 2009 found that olfactory receptors help control metabolic function and regulate blood pressure in the kidneys of mice. © 2014 The New York Times Company
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20206 - Posted: 10.14.2014
By Meredith Levine, Word went round Janice Mackay's quiet neighbourhood that she was hitting the bottle hard. She'd been seen more than once weaving along the sidewalk in front of her suburban home in Pickering, just outside Toronto, in a sad, drunken stagger. But Mackay wasn't drunk. As it turned out, her inner ear, the body's balance centre, had been destroyed by medication when she was hospitalized for over a month back in May 2005. At the time, Mackay was diagnosed with a life-threatening infection in one of her ovaries, and so was put on a cocktail of medication, including an IV drip of gentamicin, a well-known, inexpensive antibiotic that is one of the few that hasn't fallen prey to antibiotic-resistant bacteria. A few weeks later, the infection was almost gone when Mackay, still hospitalized, suddenly developed the bed spins and vomiting. Her medical team told her she'd been laying down too long and gave her Gravol, but the symptoms didn't go away. In a follow-up appointment after her discharge, Mackay was told that the dizziness was a side effect of the gentamicin, and that she would probably have to get used to it. But she didn't discover the extent of the damage until later when neurotologist Dr. John Rutka assessed her condition and concluded that the gentamicin had essentially destroyed her vestibular system, the body's motion detector, located deep within the inner ear. © CBC 2014
Link ID: 20198 - Posted: 10.13.2014
By David Shultz The next time you see a fruit fly hovering around your pint of beer, don’t swat it—appreciate it. You’re witnessing a unique relationship between yeast and insect. A new study reveals that the single-celled organisms have evolved to secrete a fruity scent that attracts fruit flies, which they hitch a ride on for greener pastures. The findings may also explain the sweet aroma of some craft beers. Like many scientific discoveries, the new work was the product of a happy accident. Kevin Verstrepen, a geneticist at KU Leuven in Belgium, was working with two types of yeast: a normal strain and another with a mutation in a gene called ATF1 that causes the cells to produce fewer odors during fermentation. “Nobody really knew what was happening until I was lazy enough to leave the lab on a Friday with these yeast left out on the bench,” he says. By coincidence, a group of fruit flies (Drosophila melanogaster) chose that weekend to escape from a neighboring genetics lab. When Verstrepen returned to work on Monday, he discovered that the insects had found their way into the smelly yeast culture but had ignored the mutant colony. To probe further, Verstrepen and colleagues set up an enclosed “arena” and pumped ATF1 aromas, which are either fruity, flowery, or solventlike, into one corner. Another corner received a dose of odors from the ATF1-deficient yeast. The remaining two corners emitted odorless streams of air to serve as controls. As expected, the flies congregated almost exclusively in the corner emitting the fragrant odors of yeast with intact ATF1 genes. Analyses of the insects’ brains revealed that the neurons in flies exposed to smelly yeast responded in an entirely different way from those exposed to odorless air or the scent of ATF1-deficient yeast strain, the researchers report online today in Cell Reports. © 2014 American Association for the Advancement of Science
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20192 - Posted: 10.11.2014