Chapter 9. Hearing, Vestibular Perception, Taste, and Smell
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By Tia Ghose, LiveScience Humans can smell fear and disgust, and the emotions are contagious, according to a new study. The findings, published Nov. 5 in the journal Psychological Science, suggest that humans communicate via smell just like other animals. "These findings are contrary to the commonly accepted assumption that human communication runs exclusively via language or visual channels," write Gün Semin and colleagues from Utrecht University in the Netherlands. Most animals communicate using smell, but because humans lack the same odor-sensing organs, scientists thought we had long ago lost our ability to smell fear or other emotions. To find out, the team collected sweat from under the armpits of 10 men while they watched either frightening scenes from the horror movie "The Shining" or repulsive clips of MTV's "Jackass." Next, the researchers asked 36 women to take a visual test while they unknowingly inhaled the scent of men's sweat. When women sniffed "fear sweat," they opened their eyes wide in a scared expression, while those smelling sweat from disgusted men scrunched their faces into a repulsed grimace. (The team chose men as the sweat donors and women as the receivers because past research suggests women are more sensitive to men's scent than vice versa.) © 2012 NBCNews.com
by Joel Winston Never mind the bitter end – it is the bitter beginning of an infection that triggers an immune response. We know that taste receptors on the tongue can detect bitter foods, but it turns out that there are also identical taste receptors in the upper airway. Noam Cohen at the University of Pennsylvania in Philadelphia and his team think they know why. They grew cell cultures from sinus tissue samples collected from surgical patients, and found that bitter taste receptors in the tissue picked up the presence of Pseudomonas aeruginosa, a bacterium that can cause pneumonia. The sinus tissue responded by producing nitric oxide to kill the invading microbes. "Certain people have strong innate defences against these bacteria, which is based on their ability to detect bitterness," says Cohen. "Others who don't really 'taste' these bitter compounds have a weakened defence." The research could lead to nasal sprays designed to activate the taste receptors and boost people's natural defences against sinus infections. "This is probably the most exciting clinical link found for bitter receptors," says Liquan Huang of the Monell Chemical Senses Center in Philadelphia, Pennsylvania, who was not involved in the study. "However, further work is needed to see if this can be translated into treatments." Journal reference: Journal of Clinical Investigation, doi.org/jj4 © Copyright Reed Business Information Ltd.
By Christina Agapakis Smell is notoriously subjective and hard to define. Odors can be perceived differently by different people depending on genetics, culture, past experience, the environment, and whether they’ve had a really bad sinus infection or not. Even worse, the same person can perceive the same smell differently at different times, depending on how the smell is described and other sensory fluctuations. Leslie Vosshall’s Laboratory of Neurogenetics and Behavior at Rockefeller University studies how complex behaviors are influenced by the chemical senses in organisms ranging from mosquitoes to humans. In order to better understand how human odor perception varies, both within individuals at different times and between different people, the lab asked nearly 400 New Yorkers to describe and rate the intensity and pleasantness of 66 different smells, at the same time collecting demographic data (significantly more diverse than the typical study of undergraduate psychology students) as well as data about their eating habits and perfume usage, finding many instances of variability in how people perceive smells. The lab recently published their extensive survey titled “An olfactory demography of a diverse metropolitan population” in the open-access journal BMC Neuroscience. They’ve also made their data freely available (you can download the huge excel file here) for further analysis or data-mining. This study has been ongoing for several years, and two years ago inspired Nicola Twilley’s wonderful Scratch-and-Sniff Map of New York’s olfactory psychogeography. Rather than mapping what people smell, the odors that they would encounter in different neighborhoods, she mapped how they smell, mapping odor preferences by neighborhood using homemade scratch-and-sniff stickers, sampling some of the variation in our smell universe. © 2012 Scientific American
Keyword: Chemical Senses (Smell & Taste)
Link ID: 17404 - Posted: 10.22.2012
By Gary Stix Oliver Sacks, HBO and others have chronicled the life of autistic savant Temple Grandin. The unique patterns of thought produced by Grandin’s brain enabled her to design now-ubiquitous methods to treat cattle more humanely, and she has served as inspiration to others diagnosed with the condition. Until now, no one has tried to assess the actual brain physiology of the professor of animal sciences at Colorado State University. Grandin herself wanted to know more about the biological basis of her cognitive strengths and deficits. So she entered into a collaboration with the University of Utah, which performed a battery of imaging tests—MRI, DTI and fMRI—to determine brain volume, cortical thickness and the structure of the insulating white matter that surrounds the long, wire-like axons that connect one brain cell with another. Supplemented with neuropsychological testing, researchers compared these results with those from three other “neurotypical” female subjects of about the same age. It turns out that Grandin’s brain appears to be similar to that of other autistic savants. She has greater volume in the right hemisphere, which might account for her superior visuospatial abilities. She also has increased thickness of the entorhinal cortex, an area involved with memory As with others with autism, she has an overall larger brain size. And the enlarged amygdala and the smaller cortical thickness in the fusiform gyrus may relate to the deficits autistic individuals experience in dealing with emotion and reading faces. “There’s this idea in the savant literature that left hemisphere damage occurs during development and the right hemisphere compensates in some way,” says Jason Cooperrider, a graduate student at the University of Utah who presented the findings at the conference. “All of the savant skills are right hemisphere-dominant abilities, which would include Dr. Grandin’s exceptional visual and spatial ability which would be considered savant level.” © 2012 Scientific American
By Ferris Jabr With the exception of the cast of Disney’s The Little Mermaid—and Big Mouth Billy Bass—fish do not spring to mind as the animal kingdom’s most vocally gifted members. But one unusual singing fish has been teaching biologists and neuroscientists a lot about speech and hearing. Its bulging eyes and blubbery lips have graced several research posters at the Society for Neuroscience’s annual meeting, which is in New Orleans, Louisiana this year. The finned crooner in question is the plainfin midshipman fish (Porichthys notatus), which belongs to a family of fish known as toadfish because of their squat, slimy appearance. Midshipman fish live along the Pacific coast from Alaska to Baja California at depths of up to 300 meters, burying themselves in the mud during the day and surfacing at night to feed. Their name is attributable to the hundreds of luminous spots called photophores that decorate their underbellies, which are somewhat reminiscent of the buttons on a naval officer’s uniform. The fish likely use these bioluminescent dots to attract small prey such as krill and to hide from predators by masking their own shadows with a camouflage technique known as counter-illumination. Midshipman fish come in three varieties: females, Type I males and the smaller Type II males. All three types are vocal, emitting short grunts to communicate with one another, but Type 1 males are the most voluble by far. In the spring and summer, Type 1 males head to shallow waters, excavate nests beneath rocks along the shoreline, hunker down and start to sing, using sonic muscles surrounding their inflatable swim bladders to hum for up to an hour at a time. This humming, which people have described a droning motorboat or an orchestra of mournful oboes, is so loud that it has been known to wake houseboat owners in San Francisco and Sausalito © 2012 Scientific American,
By HENRY FOUNTAIN SAINT-LOUIS, France — Denis Spitzer wants to beat dogs at their own game. At a binational armaments and security research center here in eastern France, Dr. Spitzer and his colleagues are working on a sensor to detect vapors of TNT and other explosives in very faint amounts, as might emanate from a bomb being smuggled through airport security. Using microscopic slivers of silicon covered with forests of even smaller tubes of titanium oxide, they aim to create a device that could supplement, perhaps even supplant, the best mobile bomb detector in the business: the sniffer dog. But emulating the nose and brain of a trained dog is a formidable task. A bomb-sniffing device must be extremely sensitive, able to develop a signal from a relative handful of molecules. And it must be highly selective, able to distinguish an explosive from the “noise” of other compounds. While researchers like Dr. Spitzer are making progress — and there are some vapor detectors on the market — when it comes to sensitivity and selectivity, dogs still reign supreme. “Dogs are awesome,” said Aimee Rose, a product sales director at the sensor manufacturer Flir Systems, which markets a line of explosives detectors called Fido. “They have by far the most developed ability to detect concealed threats,” she said. But dogs get distracted, cannot work around the clock and require expensive training and handling, Dr. Rose said, so there is a need for instruments. © 2012 The New York Times Company
When you hear the sound of a nail scratching a blackboard, the emotional and auditory part of your brain are interacting with one another, a new study reveals. The heightened activity and interaction between the amygdala, which is active in processing negative emotions, and the auditory parts of the brain explain why some sounds are so unpleasant to hear, scientists at Newcastle University have found. "It appears there is something very primitive kicking in," said Dr. Sukhbinder Kumar, the paper’s author. "It’s a possible distress signal from the amygdala to the auditory cortex." Researchers at the Wellcome Trust Centre for Neuroimaging at UCL and Newcastle University used functional magnetic resonance imaging (fMRI) to examine how the brains of 13 volunteers responded to a range of sounds. Listening to the noises inside the scanner, the volunteers rated them from the most unpleasant, like the sound of knife on a bottle, to the most pleasing, like bubbling water. Researchers were then able to study the brain response to each type of sound. "At the end of every sound, the volunteers told us by pressing a button how unpleasant they thought the sound was," Dr. Kumar said. Researchers found that the activity of the amygdala and the auditory cortex were directly proportional to the ratings of perceived unpleasantness. They concluded that the emotional part of the brain, the amygdala, in effect takes charge and modulates the activity of the auditory part of the brain, provoking our negative reaction. © CBC 2012
By Jason G. Goldman My high school biology teacher once told me that nothing was binary in biology except for alive and dead, and pregnant and not pregnant. Any other variation, he said, existed along a continuum. Whether or not the claim is technically accurate, it serves to illustrate an important feature of biological life. That is, very little in the biological world falls neatly into categories. A new finding, published today in PLoS ONE by Gustavo Arriaga, Eric P. Zhou, and Erich D. Jarvis from Duke University adds to the list of phenomena that scientists once thought were categorical but may, in fact, not be. The consensus among researchers was that, in general, animals divide neatly into two categories: singers and non-singers. The singers include songbirds, parrots, hummingbirds, humans, dolphins, whales, bats, elephants, sea lions and seals. What these species all have in common – and what distinguishes them from the non-singers of the animal world – is that they are vocal learners. That is, these species can change the composition of their sounds that emanate from the larynx (for mammals) or syrinx (for birds), both in terms of the acoustic qualities such as pitch, and in terms of syntax (the particular ordering of the parts of the song). It is perhaps not surprising that songbirds and parrots have been extremely useful as models for understanding human speech and language acquisition. When other animals, such as monkeys or non-human apes, produce vocalizations, they are always innate, usually reflexive, and never learned. But is the vocal learner/non-learner dichotomy truly reflective of biological reality? Maybe not. It turns out that mice make things more complicated. © 2012 Scientific American
By Meghan Rosen David Ferrero wasn’t expecting the jaguar to pounce. When he approached the holding pens at Massachusetts’ Stone Zoo, the big cat watched but looked relaxed, lounging on her cage’s concrete floor. Two other jaguars rested in separate cages nearby. The jaguars usually prowled outside, in the grassy grounds of the zoo’s enclosure. But this afternoon, zookeepers kept the animals inside so that Ferrero and a colleague could grab a behind-the-scenes peek. Here, the jaguars slept at night — and fed. Here, only metal bars stood between the humans and the cats. As Ferrero stepped closer to the cages, the watchful female sprang up, twisting her body toward him, front paws thumping the bars. Fully extended, she was as tall as Ferrero. “I think she wanted to eat me,” he says. The zookeepers weren’t afraid, but Ferrero flinched. He wasn’t familiar with the lean, black-spotted feline. He was just there to pick up some pee. Ferrero, a neurobiologist from Harvard, was visiting the zoo to gather urine specimens for a study linking odors to instinctual behavior in rodents. Early lab results had hinted that a whiff of a chemical in carnivore pee flashed a sort of billboard message, blinking “DANGER” in neon lights — enough to make animals automatically shrink away in fear. © Society for Science & the Public 2000 - 2012
Keyword: Chemical Senses (Smell & Taste)
Link ID: 17334 - Posted: 10.06.2012
By Jennifer Viegas Bats may have more in common with the fictional Batman than previously believed, since both successfully combine work with courting sexy potential mates -- a lot of them. A new study, published in the latest Proceedings of the Royal Society B, reveals that bat echolocation calls, primarily used for orientation and foraging, also contain information about sex, which helps the flying mammals to acquire and keep mates. The info is especially helpful to certain male bats with harems of adoring females that are actually huskier than the males. This holds true for the greater sac-winged bat (Saccopteryx bilineata), which was the focus of the study. Lead author Mirjam Knörnschild told Discovery News that "male S. bilineata court females whenever the opportunity arises. The social information in echolocation calls about the sex of the calling bat benefits listening harem males because they can distinguish between females and male rivals. It might also benefit calling females because they are greeted friendly." athletes Knörnschild, a researcher at the University of Ulm's Institute of Experimental Ecology, and her team analyzed greater sac-winged bat echolocation calls. The scientists discovered that the calls contain "pronounced vocal signatures encoding sex and individual identity." This can include species identity, age, sex, group affiliation, and other more specific information about the individual. © 2012 Discovery Communications, LLC.
By NICHOLAS BAKALAR A small study has found that obese children are more likely than others to have a weak sense of taste. German researchers tested tasting ability in 99 obese and 94 normal-weight children, whose average age was 13, by having them try to identify tastes on strips of filter paper and asking them to distinguish among sweet, sour, salty, umami (savory) and bitter. The children also were asked to rate the taste’s intensity on a five-point scale. Girls were better than boys at distinguishing tastes, and older children scored higher than younger; there were no differences by ethnicity. Obese children scored an average of 12.6 out of a possible 20, while the normal-weight children averaged 14.1, a statistically significant difference. On the intensity scale, obese children rated all flavor concentrations lower than did those in the normal-weight group. “We think it’s important, especially for young children, to get different tastes so that they can improve their taste sensitivity,” said the lead author, Dr. Johanna Overberg, a pediatrician at Charité Children’s Hospital in Berlin. “If you taste more and different things at younger ages, you can do this.” The authors, writing online in the Archives of Disease in Childhood, say the reason for the association is unclear, but they suggest that the hormone leptin may affect both body weight and the sensitivity of taste buds. Copyright 2012 The New York Times Company
By Sandra G. Boodman, The 80th birthday party for Josephine van Es marked two milestones, only one of which was apparent at the time. Held in November 2004 at her daughter’s house in Rehoboth Beach, Del., the event was a celebration of her longevity, good health and loving family. It also marked one of the last times van Es can remember feeling well and not beset by the pain that developed soon afterward and has left the inside of her mouth feeling perpetually scalded and with a constant metallic taste. “It’s awful,” said van Es, 87, who says the burning is worse than the taste, which she likens to “sucking on a penny.” Her daughter Karen van Es says that her mother’s problem has taken a toll on both their lives. For nearly eight years, she has taken time from her job at a Northern Virginia veterinary clinic to ferry her mother, who lives independently in a condominium in Lewes, Del., to doctors in Delaware, Philadelphia and Washington. She also has contacted specialists in Florida and Canada hoping one would propose an effective remedy for an ailment that took more than a year to diagnose and has so far eluded treatment. “She tells me, ‘I just feel rotten all the time,’ ” said Karen van Es, 63, an only child who speaks to her mother every day and sees her often. “My mother has lost confidence as a result of this,” Karen van Es said, adding that she often feels helpless and frustrated about not being able to do more. © 1996-2012 The Washington Post
By Mary Bates It's an oft-repeated idea that blind people can compensate for their lack of sight with enhanced hearing or other abilities. The musical talents of Stevie Wonder and Ray Charles, both blinded at an early age, are cited as examples of blindness conferring an advantage in other areas. Then there's the superhero Daredevil, who is blind but uses his heightened remaining senses to fight crime. It is commonly assumed that the improvement in the remaining senses is a result of learned behavior; in the absence of vision, blind people pay attention to auditory cues and learn how to use them more efficiently. But there is mounting evidence that people missing one sense don't just learn to use the others better. The brain adapts to the loss by giving itself a makeover. If one sense is lost, the areas of the brain normally devoted to handling that sensory information do not go unused — they get rewired and put to work processing other senses. A new study provides evidence of this rewiring in the brains of deaf people. The study, published in The Journal of Neuroscience, shows people who are born deaf use areas of the brain typically devoted to processing sound to instead process touch and vision. Perhaps more interestingly, the researchers found this neural reorganization affects how deaf individuals perceive sensory stimuli, making them susceptible to a perceptual illusion that hearing people do not experience. These new findings are part of the growing research on neuroplasticity, the ability of our brains to change with experience. A large body of evidence shows when the brain is deprived of input in one sensory modality, it is capable of reorganizing itself to support and augment other senses, a phenomenon known as cross-modal neuroplasticity. © 2012 Scientific American
by Sarah C. P. Williams Scientists have enabled deaf gerbils to hear again—with the help of transplanted cells that develop into nerves that can transmit auditory information from the ears to the brain. The advance, reported today in Nature, could be the basis for a therapy to treat various kinds of hearing loss In humans, deafness is most often caused by damage to inner ear hair cells—so named because they sport hairlike cilia that bend when they encounter vibrations from sound waves—or by damage to the neurons that transmit that information to the brain. When the hair cells are damaged, those associated spiral ganglion neurons often begin to degenerate from lack of use. Implants can work in place of the hair cells, but if the sensory neurons are damaged, hearing is still limited. "Obviously the ultimate aim is to replace both cell types," says Marcelo Rivolta of the University of Sheffield in the United Kingdom, who led the new work. "But we already have cochlear implants to replace hair cells, so we decided the first priority was to start by targeting the neurons." In the past, scientists have tried to isolate so-called auditory stem cells from embryoid bodie—aggregates of stem cells that have begun to differentiate into different types. But such stem cells can only divide about 25 times, making it impossible to produce them in the quantity needed for a neuron transplant. © 2010 American Association for the Advancement of Science.
By PERRI KLASS, M.D. When children learn to play a musical instrument, they strengthen a range of auditory skills. Recent studies suggest that these benefits extend all through life, at least for those who continue to be engaged with music. But a study published last month is the first to show that music lessons in childhood may lead to changes in the brain that persist years after the lessons stop. Researchers at Northwestern University recorded the auditory brainstem responses of college students — that is to say, their electrical brain waves — in response to complex sounds. The group of students who reported musical training in childhood had more robust responses — their brains were better able to pick out essential elements, like pitch, in the complex sounds when they were tested. And this was true even if the lessons had ended years ago. Indeed, scientists are puzzling out the connections between musical training in childhood and language-based learning — for instance, reading. Learning to play an instrument may confer some unexpected benefits, recent studies suggest. We aren’t talking here about the “Mozart effect,” the claim that listening to classical music can improve people’s performance on tests. Instead, these are studies of the effects of active engagement and discipline. This kind of musical training improves the brain’s ability to discern the components of sound — the pitch, the timing and the timbre. Copyright 2012 The New York Times Company
by Hal Hodson IF YOU can hear, you probably take sound for granted. Without thinking, we swing our attention in the direction of a loud or unexpected sound - the honk of a car horn, say. Because deaf people lack access to such potentially life-saving cues, a group of researchers from the Korea Advanced Institute of Science and Technology (KAIST) in Daejeon built a pair of glasses which allows the wearer to "see" when a loud sound is made, and gives an indication of where it came from. An array of seven microphones, mounted on the frame of the glasses, pinpoints the location of such sounds and relays that directional information to the wearer through a set of LEDs embedded inside the frame. The glasses will only flash alerts on sounds louder than a threshold level, which is defined by the wearer. Previous attempts at devices which could alert deaf users to surrounding noises have been ungainly. For example, research in 2003 at the University of California, Berkeley, used a computer monitor to provide users with a visual aid to pinpoint the location of a sound. The Korean team have not beaten this problem quite yet - the prototype requires a user to carry a laptop around in a backpack to process the signal. But lead researcher Yang-Hann Kim stresses that the device is a first iteration that will be miniaturised over the next few years. Richard Ladner at the University of Washington in Seattle questions whether the device would prove beneficial enough to gain acceptance. "Does the benefit of wearing such a device outweigh the inconvenience of having extra technology that is seldom needed?" he asks. © Copyright Reed Business Information Ltd.
Link ID: 17233 - Posted: 09.07.2012
By Susan Milius Caterpillars way too immature for actual sex turn out to detect and take an interest in adult sex pheromones. Caterpillars of the cotton leafworm moth (Spodoptera littoralis) don’t have working sex organs. They’re just long, black-green larvae eating as much as they can before transforming into the completely different body shape and lifestyle of an adult moth. Yet these caterpillars can sense, and appear to like, the adult sex pheromone of their species, an international team reports September 4 in Nature Communications. “This is a funny fact because sex pheromones are supposed to be for sex,” says coauthor Emmanuelle Jacquin-Joly of the French agricultural research agency INRA in Versailles. Adult female moths release puffs of these chemicals, and males catching a whiff — sometimes from considerable distances — sniff their way through the night to the female. Evolution may have repurposed some chemistry in this species, Jacquin-Joly and her colleagues propose. What means “come hither” to adult moths may indicate something quite different, perhaps “here’s food,” to a youngster, she says. She began looking for a cotton leafworm caterpillar pheromone response after another lab found that larval silkworm antennae make the adult-style proteins required to bind molecules of adult sex pheromones from the air and shuttle them to nerve cells. Young silkworms didn’t seem to use the information, but Jacquin-Joly wondered if young cotton leafworms, with a much broader diet, might respond differently. © Society for Science & the Public 2000 - 2012
Tuning a piano also tunes the brain, say researchers who have seen structural changes within the brains of professional piano tuners. Researchers at University College London and Newcastle University found listening to two notes played simultaneously makes the brain adapt. Brain scans revealed highly specific changes in the hippocampus, which governs memory and navigation. These correlated with the number of years tuners had been doing this job. The Wellcome Trust researchers used magnetic resonance imaging to compare the brains of 19 professional piano tuners - who play two notes simultaneously to make them pitch-perfect - and 19 other people. What they saw was highly specific changes in both the grey matter - the nerve cells where information processing takes place - and the white matter - the nerve connections - within the brains of the piano tuners. Investigator Sundeep Teki said: "We already know that musical training can correlate with structural changes, but our group of professionals offered a rare opportunity to examine the ability of the brain to adapt over time to a very specialised form of listening." Other researchers have noted similar hippocampal changes in taxi drivers as they build up detailed information needed to find their way around London's labyrinth of streets. BBC © 2012
By Christie Wilcox Music has a remarkable ability to affect and manipulate how we feel. Simply listening to songs we like stimulates the brain’s reward system, creating feelings of pleasure and comfort. But music goes beyond our hearts to our minds, shaping how we think. Scientific evidence suggests that even a little music training when we’re young can shape how brains develop, improving the ability to differentiate sounds and speech. With education funding constantly on the rocks and tough economic times tightening many parents’ budgets, students often end up with only a few years of music education. Studies to date have focused on neurological benefits of sustained music training, and found many upsides. For example, researchers have found that musicians are better able to process foreign languages because of their ability to hear differences in pitch, and have incredible abilities to detect speech in noise. But what about the kids who only get sparse musical tutelage? Does picking up an instrument for a few years have any benefits? The answer from a study just published in the Journal of Neuroscience is a resounding yes. The team of researchers from Northwestern University’s Auditory Neuroscience Laboratory tested the responses of forty-five adults to different complex sounds ranging in pitch. The adults were grouped based on how much music training they had as children, either having no experience, one to five years of training, or six to eleven years of music instruction. © 2012 Scientific American
by Emily Underwood In the Hans Christian Andersen tale "The Nightingale," a songbird melts an emperor's heart with its singing, but flies away when the ruler forces it to sing duets with a jeweled, mechanical bird that warbles only waltzes. There's a moral here, a new study suggests. Although humans have long attributed musical qualities to birdsong, cold, hard statistics show that's all an illusion. The birds we prize most for their songs sound most like the human voice, says Robert Zatorre, a cognitive neuroscientist at McGill University in Montreal, Canada, who was not involved in the study. The sounds they make have clear tones, repeat similar phrases, and are made of discrete notes. Despite these pleasing attributes, however, it has never been scientifically proven that the notes in birdsong follow the same organizational rules that govern most musical compositions. In fact, says ecologist Marcelo Araya-Salas of New Mexico State University in Las Cruces, author of the new study, no one has ever addressed the question using quantitative methods. Billions of potential notes exist between the low and high notes in an octave. But for reasons that researchers only partially understand—the physiological limits of human hearing, for example, and cultural preferences that have evolved over time—most music is based on variations of only five to 12 notes. A baby grand piano, which has 88 keys, is tuned so that each octave is divided into twelve equal intervals, called half-steps, that form the 12-note chromatic scale underlying most of Western music. The seven-note diatonic scale, "do, re, mi, fa, so, la, ti (do)," is another familiar example, as is the ancient five-note, pentatonic scale used in Greek lyre music and nearly every riff played on the electric guitar. © 2010 American Association for the Advancement of Science