Chapter 6. Hearing, Balance, Taste, and Smell
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By Alan Boyle, Science Editor, NBC News BOSTON — Neuroscientists are following through on the promise of artificially enhanced bodies by creating the ability to "feel" flashes of light in invisible wavelengths, or building an entire virtual body that can be controlled via brain waves. "Things that we used to think were hoaxes or science fiction are fast becoming reality," said Todd Coleman, a bioengineering professor at the University of California at San Diego. Coleman and other researchers surveyed the rapidly developing field of neuroprosthetics in Boston this weekend at the annual meeting of the American Association for the Advancement of Science. One advance came to light just in the past week, when researchers reported that they successfully wired up rats to sense infrared light and move toward the signals to get a reward. "This was the first attempt … not to restore a function but to augment the range of sensory experience," said Duke University neurobiologist Miguel Nicolelis, the research team's leader. The project, detailed in the journal Nature Communications, involved training rats to recognize a visible light source and poke at the source with its nose to get a sip of water. Then electrodes were implanted in a region of the rats' brains that is associated with whisker-touching. The electrodes were connected to an infrared sensor on the rats' heads, which stimulated the target neurons when the rat was facing the source of an infrared beam. Then the visible lights in the test cage were replaced by infrared lights. © 2013 NBCNews.com
by Hal Hodson CAN YOU imagine feeling Earth's magnetic field on the tip of your tongue? Strangely, this is now possible, using a device that converts the tongue into a "display" for output from environmental sensors. Gershon Dublon of the Massachusetts Institute of Technology devised a small pad containing electrodes in a 5 × 5 grid. Users put the pad, which Gershon calls Tongueduino, on their tongue. When hooked up to an electronic sensor, the pad converts signals from the sensor into small pulses of electric current across the grid, which the tongue "reads" as a pattern of tingles. Dublon says the brain quickly adapts to new stimuli on the tongue and integrates them into our senses. For example, if Tongueduino is attached to a sensor that detects Earth's magnetic field, users can learn to use their tongue as a compass. "You might not have to train much," he says. "You could just put this on and start to perceive." Dublon has been testing Tongueduino on himself for the past year using a range of environmental sensors. He will now try the device out on 12 volunteers. Blair MacIntyre at the Georgia Institute of Technology in Atlanta says a wireless version of Tongueduino could prove useful in augmented reality applications that deliver information to users inconspicuously, without interfering with their vision or hearing. "There's a need for forms of awareness that aren't socially intrusive," he says. Even Google's much-publicised Project Glass will involve wearing a headset, he points out. © Copyright Reed Business Information Ltd.
By Emily Chung, CBC News Among musicians who learned to play an instrument before the age of seven, earlier training was linked to more connections in the area of the brain that co-ordinates both hands.Among musicians who learned to play an instrument before the age of seven, earlier training was linked to more connections in the area of the brain that co-ordinates both hands. (Jorge Silva/Reuters) Starting piano or violin lessons before the age of seven appears to cause permanent changes to the brain that are linked to better motor skills. Those changes in brain development don't occur in people who learn to play an instrument when they are older, a new study has found. "What we think is that it doesn't mean you can't be an amazing musician if you start later — just that if you start earlier it may give you some of these specific abilities that are helpful," said Virginia Penhune, a Concordia University psychologist who co-authored the research with two of her doctoral students and McGill University neuropsychologist Robert Zatorre. The Montreal researchers gave a test of motor skills to and scanned the brains of 36 musicians who were either enrolled in a university music program or performed professionally, and who had an average of 16 years experience playing musical instruments. Half of them began their musical training between age three and seven, while the other half started between the ages of eight and 18, but both groups had a comparable level of experience. The study also tested 17 non-musicians. © CBC 2013
by Lizzie Wade When a male wasp decides it's time to settle down and start a family, he releases a chemical calling card in the form of pheromones, broadcasting his location, his availability, and, most importantly, his identity. Most other kinds of insects will either ignore his signal or be repelled by it, but female wasps of his own species will buzz over and get down to business. But how and why did different pheromone blends—and the species that prefer them—evolve in the first place? A new study offers a possible solution to this long-standing evolutionary mystery, suggesting that new sex pheromones may evolve through genetic mutation before potential mates develop the ability to detect them. Scientists have long been impressed by the perfect harmony of chemical communication among insects, especially when it comes to choosing mates by detecting and responding to the sex pheromones of only their own species. But scientists were puzzled by how such a delicate system evolved. If female wasps respond to only a specific blend of pheromones, males that produce even a subtly different blend shouldn't have much luck mating and passing on their mutant genes. It seemed that in order for males to evolve new pheromones, the female insects would need some preexisting adaptation that would cause them to prefer the new chemical blend. But how could they evolve a preference for something they had never encountered and should, logic suggests, find off-putting? In essence, the question is which came first, a new species or its sex pheromone? In order to answer this question, a team of researchers in Germany turned to the Nasonia vitripennis wasp, a species famous for its propensity to lay its parasitic eggs on doomed fly pupae. When the scientists analyzed the N. vitripennis male sex pheromone, they found it contained two important chemicals, which they call RS and RR. RS also turns up in the male sex pheromones of another species of wasp, N. giraulti, whereas RR appears to be unique. © 2010 American Association for the Advancement of Science.
by Kelli Whitlock Burton Having a conversation in a noisy restaurant can be difficult. For many elderly adults, it's often impossible. But with a little practice, the brain can learn to hear above the din, a new study suggests. Age-related hearing loss can involve multiple components, such as the disappearance of sensory cells in the inner ear. But scientists say that part of the problem may stem from our brains. As we get older, our brains slow down—a natural part of aging called neural slowing. One side effect of this sluggishness is the inability to process the fast-moving parts of speech, particularly consonants at the beginning of words that sound alike, such as "b," "p," "g," and "d." Add background noise to the mix and "bad" may sound like "dad," says Nina Kraus, director of the Auditory Neuroscience Laboratory at Northwestern University in Evanston, Illinois. "Neural slowing especially affects our ability to hear in a noisy background because the sounds we need to hear are acoustically less salient and because noise also taxes our ability to remember what we hear." Building on animal studies that pointed to an increase in neural speed following auditory training, Kraus and colleagues enrolled 67 people aged 55 to 70 years old with no hearing loss or dementia in an experiment. Half the group completed about 2 months of exercises with Brain Fitness, a commercially available auditory training program by Posit Science. (The team has no connection to the company.) The exercises helped participants better identify different speech sounds and distinguish between similar-sounding syllables, such as "ba" or "ta." © 2010 American Association for the Advancement of Science
By KATHERINE BOUTON At a party the other night, a fund-raiser for a literary magazine, I found myself in conversation with a well-known author whose work I greatly admire. I use the term “conversation” loosely. I couldn’t hear a word he said. But worse, the effort I was making to hear was using up so much brain power that I completely forgot the titles of his books. A senior moment? Maybe. (I’m 65.) But for me, it’s complicated by the fact that I have severe hearing loss, only somewhat eased by a hearing aid and cochlear implant. Dr. Frank Lin, an otolaryngologist and epidemiologist at Johns Hopkins School of Medicine, describes this phenomenon as “cognitive load.” Cognitive overload is the way it feels. Essentially, the brain is so preoccupied with translating the sounds into words that it seems to have no processing power left to search through the storerooms of memory for a response. Over the past few years, Dr. Lin has delivered unwelcome news to those of us with hearing loss. His work looks “at the interface of hearing loss, gerontology and public health,” as he writes on his Web site. The most significant issue is the relation between hearing loss and dementia. In a 2011 paper in The Archives of Neurology, Dr. Lin and colleagues found a strong association between the two. The researchers looked at 639 subjects, ranging in age at the beginning of the study from 36 to 90 (with the majority between 60 and 80). The subjects were part of the Baltimore Longitudinal Study of Aging. None had cognitive impairment at the beginning of the study, which followed subjects for 18 years; some had hearing loss. Copyright 2013 The New York Times Company
by Jacob Aron The mystery of how our brains perceive sound has deepened, now that musicians have smashed a limit on sound perception imposed by a famous algorithm. On the upside this means it should be possible to improve upon today's gold-standard methods for audio perception. Devised over 200 years ago, the Fourier transform is a mathematical process that splits a sound wave into its individual frequencies. It is the most common method for digitising analogue signals and some had thought that brains make use of the same algorithm when turning the cacophony of noise around us into individual sounds and voices. To investigate, Jacob Oppenheim and Marcelo Magnasco of Rockefeller University in New York turned to the Gabor limit, a part of the Fourier transform's mathematics that makes the determination of pitch and timing a trade-off. Rather like the uncertainty principle of quantum mechanics, the Gabor limit states you can't accurately determine a sound's frequency and its duration at the same time. 13 times better The pair reasoned that if people's hearing obeyed the Gabor limit, this would be a sign that they were using the Fourier transform. But when 12 musicians, some instrumentalists, some conductors, took a series of tests, such as judging slight changes in the pitch and duration of sounds at the same time, they beat the limit by up to a factor of 13. © Copyright Reed Business Information Ltd.
Link ID: 17775 - Posted: 02.09.2013
By Tina Hesman Saey The common mole may be homely but its nose is a wonder to behold. The eastern American mole, also known as the common mole, tracks down an earthworm treat by recognizing the slightly different odor cues entering each nostril, neurobiologist Kenneth Catania of Vanderbilt University in Nashville reports online February 5 in Nature Communications. The finding suggests that even though mole nostrils are separated by a fraction of a centimeter, each gets its own scent information that can guide an animal’s actions. “It’s an elegant demonstration of what many people suspected,” says Peter Brunjes, a neuroscientist at the University of Virginia. Previous experiments with people and rats had reached contradictory conclusions regarding whether smell, like sight and hearing, is a bilateral sense. Catania never expected the common mole, Scalopus aquaticus, to have uncommon abilities. “I’ve described it as the unlucky, stupid cousin of the star-nosed mole,” he says. Star-nosed moles, Condylura cristata, have an incredible sense of touch in their tentacled schnozzes and are among the world’s fastest foragers. But compared with other mole species, the eastern American mole has a poor sense of touch. The animals also can’t see. Catania turned to common moles because he thought they would have a hard time finding food and could be tested against star-nosed moles in future experiments. But when he placed a common mole in a semicircular arena with a chopped up bit of earthworm as bait, he says, “it would wiggle its nose around and go in a beeline toward the food.” © Society for Science & the Public 2000 - 2013
Keyword: Chemical Senses (Smell & Taste)
Link ID: 17768 - Posted: 02.06.2013
By C. CLAIBORNE RAY Q. Nearing 70, I have increasing difficulty hearing conversations, yet music in restaurants is too loud. Why? A. Age-related hearing loss, called presbycusis, is characterized by loss of hair cells in the base of the cochlea, or inner ear, that are attuned to capture and transmit high-frequency sounds, said Dr. Anil K. Lalwani, director of otology, neurotology and skull-base surgery at NewYork-Presbyterian Hospital/Columbia University Medical Center. Loss of high-frequency hearing leads to deterioration in the ability to distinguish words in conversation. Additionally, any noise in the environment leads to even greater loss in clarity of hearing. “Contrary to expectation, presbycusis is also associated with sensitivity to loud noises,” Dr. Lalwani said. “This is due to a poorly understood phenomenon called recruitment.” Normally, a specific sound frequency activates a specific population of hair cells located at a specific position within the cochlea. With hearing loss, this specificity is lost, and a much larger population of hair cells in the adjacent areas is “recruited” and also activated, producing sensitivity to noise. “Patients with presbycusis perceive an incremental increase in loudness to be much greater than those with normal hearing,” he said. “This explains why the elderly parent complains that ‘I am not deaf!’ ” when a son or daughter repeats a misheard sentence. © 2013 The New York Times Company
By James Gallagher Health and science reporter, BBC News A tiny "genetic patch" can be used to prevent a form of deafness which runs in families, according to animal tests. Patients with Usher syndrome have defective sections of their genetic code which cause problems with hearing, sight and balance. A study, published in the journal Nature Medicine, showed the same defects could be corrected in mice to restore some hearing. Experts said it was an "encouraging" start. There are many types of Usher syndrome tied to different errors in a patient's DNA - the blueprint for building every component of the body. One of those mutations runs in families descended from French settlers in North America. When they try to build a protein called hormonin, which is needed to form the tiny hairs in the ear that detect sound, they do not finish the job. It results in hearing loss at birth and has a similar effect in the eye where it causes a gradual loss of vision. Scientists at the Rosalind Franklin University of Medicine and Science, in Chicago in the US, designed a small strip of genetic material which attaches to the mutation and keeps the body's factories building the protein. There has been something of a flurry of developments in restoring hearing in the past year. BBC © 2013
by Elizabeth Pennisi Though often associated with dirty environments, cockroaches are actually quite fastidious, especially when it comes to their antennae. They clean them often by grabbing one in with a front leg and drawing it through their mouth. Researchers have long observed that many insects groom themselves, and now they know why. When scientists restrained American cockroaches or prevented grooming by gluing mouthparts for 24 hours, they noticed a shiny, waxy buildup on the antennae that clogs the tiny pores that lead to odor-sensing cells. Measurements of the electrical activity in those cells in response to sex-attractant and food odors showed that the gunk interfered with the roach's sense of smell, they report online today in the Proceedings of the National Academy of Sciences. The insects appear to produce wax continuously, likely to keep from drying out, and grooming helps remove the excess as well as dust and other foreign chemicals that land on the antennae and get trapped in the gunk. Carpenter ants, houseflies, and German cockroaches also suffered from gunk overload when prohibited from grooming, suggesting that fastidiousness is widespread. © 2010 American Association for the Advancement of Science
Keyword: Chemical Senses (Smell & Taste)
Link ID: 17755 - Posted: 02.05.2013
by Elizabeth Devitt Birds may not have big brains, but they know how to navigate. They wing around town and across continents with amazing accuracy, while we watch and wonder. Biologists believe that sight, smell, and an internal compass all contribute to avian orienteering. But none of these skills completely explains how birds fly long distances or return home from places they've never been. A new study proposes that the animals use infrasound—low-level background noise in our atmosphere—to fly by "images" they hear. These acoustical maps may also explain how other creatures steer. Scientists have long considered infrasound as a navigational cue for birds. But until U.S. Geological Survey geophysicist Jonathan Hagstrum in Menlo Park, California, became intrigued by the unexplained loss of almost 60,000 pigeons during a race from France to England in 1997, no one pinpointed how the process worked. The race went bust when the birds' flight route crossed that of a Concorde jet, and Hagstrum wanted to know why. "When I realized the birds in that race were on the same flight path as the Concorde, I knew it had to be infrasound," he says. The supersonic plane laid down a sonic boom when most of the animals were flying across the English Channel. Normally, infrasound is generated when deep ocean waves send pressure waves reverberating into the land and atmosphere. Infrasound can come from other natural causes, such as earthquakes, or humanmade events, such as the acceleration of the Concorde. The long, slow waves move across vast distances. Although humans can't hear them, birds and other animals are able to tune in. © 2010 American Association for the Advancement of Science
By Jason Palmer Science and technology reporter, BBC News A controversial theory that the way we smell involves a quantum physics effect has received a boost, following experiments with human subjects. It challenges the notion that our sense of smell depends only on the shapes of molecules we sniff in the air. Instead, it suggests that the molecules' vibrations are responsible. A way to test it is with two molecules of the same shape, but with different vibrations. A report in PLOS ONE shows that humans can distinguish the two. Tantalisingly, the idea hints at quantum effects occurring in biological systems - an idea that is itself driving a new field of science, as the BBC feature article Are birds hijacking quantum physics? points out. But the theory - first put forward by Luca Turin, now of the Fleming Biomedical Research Sciences Centre in Greece - remains contested and divisive. The idea that molecules' shapes are the only link to their smell is well entrenched, but Dr Turin said there were holes in the idea. He gave the example of molecules that include sulphur and hydrogen atoms bonded together - they may take a wide range of shapes, but all of them smell of rotten eggs. "If you look from the [traditional] standpoint... it's really hard to explain," Dr Turin told BBC News. "If you look from the standpoint of an alternative theory - that what determines the smell of a molecule is the vibrations - the sulphur-hydrogen mystery becomes absolutely clear." BBC © 2013
Keyword: Chemical Senses (Smell & Taste)
Link ID: 17724 - Posted: 01.28.2013
by Sarah C. P. Williams You might not be able to pick your fingerprint out of an inky lineup, but your brain knows what you smell like. For the first time, scientists have shown that people recognize their own scent based on their particular combination of major histocompatibility complex (MHC) proteins, molecules similar to those used by animals to choose their mates. The discovery suggests that humans can also exploit the molecules to differentiate between people. "This is definitely new and exciting," says Frank Zufall, a neurobiologist at Saarland University's School of Medicine in Homburg, Germany, who was not involved in the work. "This type of experiment had never been done on humans before." MHC peptides are found on the surface of almost all cells in the human body, helping inform the immune system that the cells are ours. Because a given combination of MHC peptides—called an MHC type—is unique to a person, they can help the body recognize invading pathogens and foreign cells. Over the past 2 decades, scientists have discovered that the molecules also foster communication between animals, including mice and fish. Stickleback fish, for example, choose mates with different MHC types than their own. Then, in 1995, researchers conducted the now famous "sweaty T-shirt study," which concluded that women prefer the smell of men who have different MHC genes than themselves. But no studies had shown a clear-cut physiological response to MHC proteins. © 2010 American Association for the Advancement of Science
Keyword: Chemical Senses (Smell & Taste)
Link ID: 17716 - Posted: 01.26.2013
By Laura Sanders Older people with hearing loss may suffer faster rates of mental decline. People who have hearing trouble suffered meaningful impairments in memory, attention and learning about three years earlier than people with normal hearing, a study published online January 21 in JAMA Internal Medicine reveals. The finding bolsters the idea that hearing loss can have serious consequences for the brain, says Patricia Tun of Brandeis University in Waltham, Mass., who studies aging. “I’m hoping it will be a real wake-up call in terms of realizing the importance of hearing.” Compared with other senses, hearing is often overlooked, Tun says. “We are made to interact with language and to listen to each other, and it can have damaging effects if we don’t.” Frank Lin of Johns Hopkins School of Medicine and colleagues tested the hearing of 1,984 older adults. Most of the participants, who averaged 77 years old, showed some hearing loss — 1,162 volunteers had trouble hearing noises of less than 25 decibels, comparable to a whisper or rustling leaves. The volunteers’ deficits reflect the hearing loss in the general population: Over half of people older than 70 have trouble hearing. Over the next six years, these participants underwent mental evaluations that measured factors such as short-term memory, attention and the ability to quickly match numbers to symbols. Everybody got worse at the tasks as time wore on, but people with hearing loss had an especially sharp decline, the team found. On average, a substantial drop in performance would come about three years earlier to people with hearing loss. © Society for Science & the Public 2000 - 2013
by Jennifer Viegas The world’s largest archive of animal vocalizations and other nature sounds is now available online. This resource for students, filmmakers, scientists and curious wildlife aficionados took archivists a dozen years to assemble and make ready for the web. “In terms of speed and the breadth of material now accessible to anyone in the world, this is really revolutionary,” audio curator Greg Budney said in a press release, describing the milestone just achieved by the Macaulay Library archive at the Cornell Lab of Ornithology. “This is one of the greatest research and conservation resources at the Cornell Lab,” added Budney. “And through its digitization, we’ve swung the doors open on it in a way that wasn’t possible 10 or 20 years ago.” The collection goes way back to 1929. It contains nearly 150,000 digital audio recordings equaling more than 10 terabytes of data with a total run time of 7,513 hours. About 9,000 species are represented. Many are birds, but the collection also includes sounds of whales, elephants, frogs, primates and more. “Our audio collection is the largest and the oldest in the world,” explained Macaulay Library director Mike Webster. “Now, it’s also the most accessible. We’re working to improve search functions and create tools people can use to collect recordings and upload them directly to the archive. Our goal is to make the Macaulay Library as useful as possible for the broadest audience possible.” © 2013 Discovery Communications, LLC
Search recordings by species: 135793 recordings found
by Elizabeth Norton To humans, all fire ants may look alike. But the tiny, red, stinging bugs known as Solenopsis invicta have two types of social organization, and these factions are as recognizable to the ants as rival football teams are to us. Researchers once thought that the groups' distinct physiological and behavioral profiles stemmed from a variant in a single gene. Now, a new study provides the first evidence that the gene in question is bound up in a bundle of some 600 other genes, versions of which are all inherited together. This "supergene" takes up a large chunk of what may be the first known social chromosome, analogous to the chromosomes that determine sex in humans. The differences between the two types of fire ants start with the winged queens, according to evolutionary geneticist Laurent Keller of the University of Lausanne in Switzerland. A so-called monogyne queen is large, fat, and fertile. Once she's mated, she can fly long distances to start her colony, nourishing her eggs from her fat stores, and then wait until her larvae grow up into workers. A monogyne colony will accept only the original queen and kill any other that shows up; these ants are very aggressive in general. By contrast, a polygyne queen is smaller and needs mature workers to help set up a colony. Thus polygyne communities will accept multiple queens from nearby nests—unless, that is, one happens to be a monogyne, in which case, they kill her. In 1998, working with entomologist and geneticist Kenneth Ross of the University of Georgia in Athens, Keller showed that the two groups of fire ants had distinct versions of a gene known as Gp-9. All of the monogynes had two copies of one form; among the polygynes, many had one normal and one mutated copy of the gene. At first glance, the finding made sense. © 2010 American Association for the Advancement of Science.
by Gretchen Vogel All you graying, half-deaf Def Leppard fans, listen up. A drug applied to the ears of mice deafened by noise can restore some hearing in the animals. By blocking a key protein, the drug allows sound-sensing cells that are damaged by noise to regrow. The treatment isn't anywhere near ready for use in humans, but the advance at least raises the prospect of restoring hearing to some deafened people. When it comes to hearing, hair cells in the inner ear, so named for their bristlelike appearance, keep the process humming along, converting mechanical vibrations caused by sound waves into nerve impulses. Unfortunately for people, loud noises can overwork and destroy the cells. And once they're gone, they're gone: Birds and fish can regenerate the inner ear hair cells, but mammals cannot. Researchers have been looking for ways to reactivate the regenerative potential that other species enjoy. In 2005, scientists used gene therapy to prompt the growth of hair cells in the inner ears of adult guinea pigs, which restored some hearing. However, the drug approach would potentially be much easier to use in the clinic, says Albert Edge, a stem cell biologist at the Massachusetts Eye and Ear Infirmary in Boston. He and his colleagues had previously found that a class of drugs called gamma-secretase inhibitors could prompt the growth of hair cells from inner ear stem cells growing in the lab. The lab also showed that the drugs worked by blocking the signaling of the Notch protein, which helps determine which cells become hair cells and which become support cells during ear development. © 2010 American Association for the Advancement of Science
By Diane Mapes The video touched millions: An 8-month old boy smiles with unabashed adoration at his mother as he hears her voice, seemingly for the first time, thanks to a new cochlear implant. Posted on YouTube in April of 2008, the video of "Jonathan's Cochlear Implant Activation" has received more than 3.6 million hits and thousands of comments from viewers, many clamoring for an update. Five-year-old Jonathan is “doing great,” according to his parents, Brigette and Mark Breaux of Houston, Texas. "He's in kindergarten and we're working on speech," Brigette, his 35-year-old stay-at-home mom, told TODAY.com. "He can hear everything that we say to him. It's of course artificial hearing but he can hear and understand what we're saying." After a bout with bacterial meningitis left him deaf, Jonathan Breaux regained hearing with the help of a cochlear implant, and is now a happy 5-year-old. "He's a flirt," adds Mark, a 36-year-old corporate controller. "He was chasing girls around the playground when Brigette went to see him for his class party. He's a handful." © 2013 NBCNews.com