Chapter 6. Hearing, Balance, Taste, and Smell
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By Nick Lavars Keeping ourselves upright is something most of us shouldn't need to think a whole lot about, given we've been doing it almost our entire lives. But when it comes to dealing with more precarious terrain, like walking on ice or some sort of tight rope, you might think some pretty significant concentration is required. But researchers have found that even in our moments of great instability, our subconsciousness is largely responsible for keeping us from landing on our backsides. This is due to what scientists are describing as a mini-brain, a newly mapped bunch of neurons in the spinal cord which processes sensory information and could lead to new treatment for ailing motor skills and balance. "How the brain creates a sensory percept and turns it into an action is one of the central questions in neuroscience," says Martin Goulding, senior author of the research paper and professor at the Salk Institute. "Our work is offering a really robust view of neural pathways and processes that underlie the control of movement and how the body senses its environment. We’re at the beginning of a real sea change in the field, which is tremendously exciting.” The work of Goulding and his team focuses on how the body processes light touch, in particular the sensors in our feet that detect changes in the surface underfoot and trigger a reaction from the body. "Our study opens what was essentially a black box, as up until now we didn’t know how these signals are encoded or processed in the spinal cord," says Goulding. "Moreover, it was unclear how this touch information was merged with other sensory information to control movement and posture."
Keyword: Movement Disorders
Link ID: 20561 - Posted: 02.07.2015
By Monique Brouillette When the first four-legged creatures emerged from the sea roughly 375 million years ago, the transition was anything but smooth. Not only did they have to adjust to the stress of gravity and the dry environment, but they also had to wait another 100 million years to evolve a fully functional ear. But two new studies show that these creatures weren’t deaf; instead, they may have used their lungs to help them hear. Fish hear easily underwater, as sound travels in a wave of vibration that freely passes into their inner ears. If you put a fish in air, however, the difference in the density of the air and tissue is so great that sound waves will mostly be reflected. The modern ear adapted by channeling sound waves onto an elastic membrane (the eardrum), causing it to vibrate. But without this adaptation, how did the first land animals hear? To answer this question, a team of Danish researchers looked at one of the closest living relatives of early land animals, the African lungfish (Protopterus annectens). As its name suggests, the lungfish is equipped with a pair of air-breathing lungs. But like the first animals to walk on land, it lacks a middle ear. The researchers wanted to determine if the fish could sense sound pressure waves underwater, so they filled a long metal tube with water and placed a loudspeaker at one end. They played sounds into the tube in a range of frequencies and carefully positioned the lungfish in areas of the tube where the sound pressure was high. Monitoring the brain stem and auditory nerve activity in the lungfish, the researchers were surprised to discover that the fish could detect pressure waves in frequencies above 200 Hz. © 2015 American Association for the Advancement of Science
By Tina Hesman Saey Gustometer guhs-TOH-meh-ter n. A device used to squirt measured amounts of liquids into the mouth of a person in a taste study. Researchers often pair the instrument with brain scanning technology. Recently, a study of wine tasting pitted 10 of the top sommeliers from France and Switzerland against 10 novices. Researchers led by Lionel Pazart of Besançon University Hospital in France custom-built a gustometer to conduct the blind taste test. The scientists compared how brain activity changed when people tasted chardonnay, pinot noir or water. When sipping wine, the experts had greater activity in several parts of their brains, including regions involved in memory, than novices did, the researchers report in October in Frontiers in Behavioral Neuroscience. Sommeliers’ expertise may allow them to process sensory input about a wine — its taste and bouquet — while simultaneously recalling other information, such as the reputation of the winery that produced the beverage. Citations L. Pazart et al. An fMRI study on the influence of sommeliers’ expertise on the integration of flavor. Frontiers in Behavioral Neuroscience Vol. 8, October 16, 2014. doi: 10.3389/fnbeh.2014.00358. © Society for Science & the Public 2000 - 2015.
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20516 - Posted: 01.26.2015
|By Gareth Cook What is flavor? Beginning with this simple question, the Pulitzer prize-winning journalist John McQuaid weaves a fascinating story with a beginning some half a billion years ago. In his new book, Tasty, McQuaid argues that the sense of taste has played a central role in the evolution of humans. McQuaid’s tale is about science, but also about culture, history and, one senses, our future. What made you decide to write a book about taste? I have two kids, a boy and a girl born two years apart – now teens – and a few years ago, I became fascinated with how their tastes and preferences in food differed. My son liked extremes, especially super-hot chili peppers and whole lemons and limes. My daughter hated that stuff. She preferred bland comfort foods such as mashed potatoes, pasta, cheese and rice. White foods. Both kids were also picky eaters. They liked what they liked, and it didn’t overlap (except for pizza). Speaking as a parent, this was maddening. So I wondered where these differences came from. Were they genetic? The kids had mostly the same genes. Environment? They lived in the same place. And yet clearly both genes and environment were in play somehow. So I began to look into the question, and a whole world opened up. And the basic answer to my original question is: kids are, biologically speaking, weird creatures. Pickiness seems to be programmed by evolution: it would have protected small children from eating strange, possibly poisonous items. Certain preferences, meanwhile, can develop arbitrarily and become very strong, then suddenly fade – every kid goes through phases as the brain matures and the neural networks that shape perception and behavior grow. Each person’s sense of flavor is like a snowflake or a fingerprint, in this way, shaped by partly by genes, but largely by experience. And always changing as more meals are eaten. © 2015 Scientific American
By ANDREW POLLACK Driving to a meeting in 2008, Jay Lichter, a venture capitalist, suddenly became so dizzy he had to pull over and call a friend to take him to the emergency room. The diagnosis: Ménière’s disease, a disorder of the inner ear characterized by debilitating vertigo, hearing loss and tinnitus, or ringing in the ears. But from adversity can spring opportunity. When Mr. Lichter learned there were no drugs approved to treat Ménière’s, tinnitus or hearing loss, he started a company, Otonomy. It is one of a growing cadre of start-ups pursuing drugs for the ear, an organ once largely neglected by the pharmaceutical industry. Two such companies, Otonomy and Auris Medical, went public in 2014. Big pharmaceutical companies like Pfizer and Roche are also exploring the new frontier. A clinical trial recently began of a gene therapy being developed by Novartis that is aimed at restoring lost hearing. The sudden flurry of activity has not yet produced a drug that improves hearing or silences ringing in the ears, but some companies are reporting hints of promise in early clinical trials. There is a huge need, some experts say. About 48 million Americans have a meaningful hearing loss in at least one ear; 30 million of them have it in both ears, said Dr. Frank R. Lin, an associate professor of otolaryngology and geriatric medicine at Johns Hopkins University. That figure is expected to increase as baby boomers grow older. © 2015 The New York Times Company
Link ID: 20466 - Posted: 01.10.2015
By SINDYA N. BHANOO That bats use echolocation to navigate and to find food is well known. But some blind people use the technique, too, clicking their tongues and snapping fingers to help identify objects. Now, a study reports that human echolocators can experience illusions, just as sighted individuals do. Gavin Buckingham, a psychology lecturer at Heriot-Watt University in Scotland, and his colleagues at the University of Western Ontario asked 10 study subjects to pick up strings attached to three boxes of identical weight but different sizes. Overwhelmingly, the sighted individuals succumbed to what is known as the “size-weight illusion.” The bigger boxes felt lighter to them. Blind study subjects who picked up each of the three strings did not experience the illusion. They correctly surmised that the boxes were of equal weight. But blind participants who relied on echolocation to get a sense of the box sizes before picking up the strings fell into the same trap as the sighted subjects and misjudged the weights. The research, published in the journal Psychological Science, supports other research suggesting that echolocation techniques may stimulate the brain in ways that resemble visual input. “It does mean this is more than a functional tool,” Dr. Buckingham said. Echolocation “doesn’t help them appreciate art or tell the difference between the color red or color blue, but it’s a step in that direction.” © 2015 The New York Times Company
by Bethany Brookshire Rats stink. First there’s the poop smell and the urine. And then there’s just that smell of rat — a kind of dusty, hairy little smell. But it turns out that rats don’t smell quite the same all the time. When they are stressed, they produce a different odor, one that makes other rats anxious. Now, Hideaki Inagaki and colleagues at the University of Tokyo in Japan have isolated the particular stress-related odor and identified the two specific chemicals behind it. The results reveal the first evidence of an isolated anxiety pheromone in rats, and give reason for scientists to look at — or maybe sniff — their behavioral experiments cautiously. And the findings could also offer glimmerings of a new flavor of rat-be-gone. Pheromones are chemicals that give off distinct odors that allow an animal to communicate within its own ranks. In rats, as in many other animals, many pheromones activate the vomeronasal organ, a small patch of cells at the base of the nasal cavity. Other researchers have found evidence of pheromones in maternal behavior and in the response of rat pups to their mothers. In the new study, the pheromones in question are about alarm and anxiety. Study coauthor Yasushi Kiyokawa of The University of Tokyo says he first came across the alarm odor when he was a graduate student. “I noticed the rats released a specific odor when I handled them for the first time, as they were stressed by the novel handling procedure,” he recalls. He went sniffing to find the source. “I found that the intensity of the odor was strongest around the anal region,” he says. Many mammals have glands around the anus that produce oils and odors. Since that first whiff of a clue, Kiyokawa and colleagues at the University of Tokyo have been working with what they called the “alarm pheromone.” While rats may be smelly to some, Kiyokawa says this particular smell isn’t unpleasant. “Like a hay or dried grass,” he says. “At least for me.” © Society for Science & the Public 2000 - 2014
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