Chapter 9. Hearing, Vestibular Perception, Taste, and Smell
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Lights, sound, action: we are constantly learning how to incorporate outside sensations into our reactions in specific situations. In a new study, brain scientists have mapped changes in communication between nerve cells as rats learned to make specific decisions in response to particular sounds. The team then used this map to accurately predict the rats’ reactions. These results add to our understanding of how the brain processes sensations and forms memories to inform behavior. “We’re reading the memories in the brain,” said Anthony Zador, M.D., Ph.D., professor at Cold Spring Harbor Laboratory, New York, and senior author of the study, published in Nature. The work was funded by the National Institutes of Health and led by Qiaojie Xiong, Ph.D., a former postdoctoral researcher in Dr. Zador’s laboratory. “For decades scientists have been trying to map memories in the brain,” said James Gnadt, Ph.D., a program director at the National Institute of Neurological Disorders and Stroke (NINDS), one of the NIH institutes that funded the study. “This study shows that scientists can begin to pinpoint the precise synapses where certain memories form and learning occurs.” The communication points, or synapses, that Dr. Zador’s lab studied were in the striatum, an integrating center located deep inside the brain that is known to play an important role in coordinating the translation of thoughts and sensations into actions. Problems with striatal function are associated with certain neurological disorders such as Huntington’s disease in which affected individuals have severely impaired skill learning.
Tristram Wyatt This Valentine’s Day, like every year, there was a rash of stories in the news about sexy smells and pheromones. You could be forgiven for thinking that human ‘sex pheromones’, in particular the ‘male molecule’ androstadienone, were well established: countless ‘human pheromones’ websites sell it and there are tens of apparently scientific studies on androstadienone published in science journals. These studies are cited hundreds of times and have ended up being treated as fact in books on sexual medicine and even commentary on legislation. The birth place of the pheromone myth was a 1991 conference in Paris sponsored by a US corporation, EROX, which had an interest in patenting androstadienone and another molecule - estratetraenol, from women - as ‘human pheromones’. Unwittingly, leading mammalian olfaction scientists lent the conference credibility. Slotted into the programme and conference proceedings was the short ‘study-zero’ paper on the ‘Effect of putative pheromones on the electrical activity of the human vomeronasal organ and olfactory epithelium’. To my surprise, the authors gave no details at all of how these molecules had been extracted, identified, and tested in bioassays - all routinely required steps in the exhaustive process before any molecule can be shown to be a species-wide chemical signal, a pheromone. Instead there was just a footnote: ‘These putative pheromones were supplied by EROX Corporation’. The missing, essential details were never published. (The claim by EROX-sponsored scientists that adult humans have a functioning vomeronasal organ, against all the evidence, is a story for another day). © 2015 Guardian News and Media Limited
by Catherine de Lange You won't believe you do it, but you do. After shaking hands with someone, you'll lift your hands to your face and take a deep sniff. This newly discovered behaviour – revealed by covert filming – suggests that much like other mammals, humans use bodily smells to convey information. We know that women's tears transmit chemosensory signals - their scent lowers testosterone levels and dampens arousal in men - and that human sweat can transmit fear. But unlike other mammals, humans don't tend to go around sniffing each other. Wondering how these kinds of signals might be exchanged, Noam Sobel and his colleagues at the Weizmann Institute of Science in Rehovot, Israel turned to one of the most common ways in which people touch each other - shaking hands. "We started looking at people and noticed that afterwards, the hand somehow inadvertently reached the face," says Sobel. To find out if people really were smelling their hands, as opposed to scratching their nose, for example, his team surreptitiously filmed 153 volunteers. Some were wired up to a variety of physiological instruments so that airflow to the nose could be measured without them realising this was the intention. The volunteers were filmed as they greeted a member of the team, either with or without a handshake. The researchers recorded how often the volunteers lifted their hands close to their nose, and how long they kept them there, the minute before and after the greeting. © Copyright Reed Business Information Ltd.
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20645 - Posted: 03.04.2015
// by Jennifer Viegas It’s long been suspected that males of many species, including humans, can sniff out whether a female is pregnant, and now new research suggests that some — if not all — female primates release a natural “pregnancy perfume” that males can probably detect. What’s more, such scents appear to broadcast whether the mom-to-be is carrying a boy or a girl. The study, published in the journal Biology Letters, focused on lemurs as a model for primates. It presents the first direct evidence in any animal species that a pregnant mother’s scent differs depending on the sex of her baby. The scent signatures “may help guide social interactions, potentially promoting mother–infant recognition, reducing intragroup conflict” or sort out paternity, wrote authors Jeremy Crawford and Christine Drea. The latter presents a loaded scenario, as it could be that males can sense — even before the birth — whether they fathered the baby. The researchers additionally suspect that odors advertising fetal sex may help dads and moms prepare for what’s to come. Crawford, from the University of California, Berkeley, and Drea, from Duke University, used cotton swabs to collect scent secretions from the genital regions of 12 female ringtailed lemurs at the Duke Lemur Center in Durham, N.C., before and during pregnancy. The scientists next used chemical analysis to identify the hundreds of ingredients that make up each female’s scent change during pregnancy. A surprising finding from this is that expectant lemur moms give off simpler scents that contain fewer odor compounds compared with their pre-pregnancy bouquet. The change is more pronounced when the moms are carrying boys, Drea said. © 2015 Discovery Communications, LLC.
By Barron H. Lerner, M.D. I can’t stand it when someone behind me at a movie chews popcorn with his or her mouth open. I mean, I really can’t stand it. I have misophonia, a condition with which certain sounds can drive someone into a burst of rage or disgust. Although only identified and named in the last 20 years, misophonia has been enthusiastically embraced, with websites, Facebook pages and conferences drawing small armies of frustrated visitors. As a primary care physician, I find that misophonia can present some special challenges: At times, my patients can be the source of annoying sounds. At other times, the condition can be a source of special bonding if I realize that a patient is a fellow sufferer. But some experts question whether misophonia really exists. By naming it, are we giving too much credence to a series of symptoms that are no big deal? Coined by the married researchers Margaret and Pawel Jastreboff of Emory University in 2002, misophonia (“hatred of sound”) is sometimes referred to as selective sound sensitivity syndrome. Like me, those with the disorder identify a series of specific sounds that bother them. A2013 study by Arjan Schröder and his colleagues at the University of Amsterdam identified the most common irritants as eating sounds, including lip smacking and swallowing; breathing sounds, such as nostril noises and sneezing; and hand sounds, such as typing and pen clicking. The range of responses to these noises is broad, from irritation to disgust to anger. Some sufferers even respond with verbal or physical aggression to those making the noises. One woman reported wanting to strangle her boyfriend in response to his chewing. © 2015 The New York Times Company
Maanvi Singh Your tongue doubtless knows the difference between a high-fat food and the low-fat alternative. Full-fat ice cream and cream cheese feel silkier and more sumptuous. Burgers made with fatty meat are typically juicer than burgers made with lean meat. OK, so, we've long known fat gives food a desirable texture. But some scientists are now making the case that we should also think of fat as the sixth primary taste, along with sweet, salt, sour, bitter and umami. Early in February, researchers from Deakin University in Australia published a paper in the journal Flavour arguing that "the next 5 to 10 years should reveal, conclusively, whether fat can be classified as the sixth taste." So what would it take for fat to become an official taste? "Strictly speaking, taste is a chemical function," Russell Keast, a sensory scientist at Deakin and lead author of the paper, tells The Salt. He says that when a chemical substance – a salt or sugar crystal, for example — comes into contact with sensory cells in our mouths, it triggers a series of reactions. The cells in our mouths tell other nerve cells that they're perceiving something sweet or salty and those nerve cells eventually pass this information on to the brain. According to the paper, there are five criteria that need to be met to call something a primary taste. It starts with a chemical stimuli (like sugar or salt), which then trigger specific receptors on our taste buds. Then, there has to be a viable a pathway between these receptors and our brains, and we've got to be able to perceive and process the taste in the brain. And finally, this whole process has to trigger downstream effects in the body. © 2015 NPR
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20596 - Posted: 02.21.2015
By Warren Cornwall The green wings of the luna moth, with their elegant, long tails, aren’t just about style. New research finds they also help save the insect from becoming a snack for a bat. The fluttering tails appear to create an acoustic signal that is attractive to echolocating bats, causing the predators to zero in on the wings rather than more vital body parts. Scientists pinned down the tails’ lifesaving role by taking 162 moths and plucking the tails off 75 of them. They used fishing line to tether two moths—one with tails, the other without—to the ceiling of a darkened room. Then, they let loose a big brown bat. The bats caught 81% of the tailless moths, but just 35% of those with fully intact wings, they report in a study published online today in the Proceedings of the National Academy of Sciences. High-speed cameras helped show why. In 55% of attacks on moths with tails, the bats went after the tails, often missing the body. It’s the first well-documented example of an organism using body shape to confuse predators that use echolocation, the researchers say—the equivalent of fish and insects that display giant eyespots for visual trickery. © 2015 American Association for the Advancement of Science
Dr. Lisa Sanders. On Wednesday, we challenged Well readers to take on the case of a 21-year-old college student with chronic headaches who suddenly became too dizzy to walk. She had a medical history that was complicated by back surgery and a subsequent infection, and chronic headaches after a car accident. More than 300 of you wrote in with suggested diagnoses, but only a handful of you noticed the clue that led the medical student who saw the patient to the right answer. The cause of the young woman’s dizziness was… Postural tachycardia syndrome, or POTS. The first reader to make this diagnosis was Theresa Baker, a retired bookkeeper and mother from Philomath, Ore. She said she immediately recognized the disorder because her young niece has suffered from it for over a decade. Her episodes of dizziness and fainting had started when she was just 13. Well done, Ms. Baker! The Diagnosis Postural tachycardia syndrome — also called postural orthostatic tachycardia syndrome — is an unusual condition in which simply being upright causes symptoms of lightheadedness, sometimes to the point of fainting, along with an increase in heart rate faster than 130 beats per minute, all of which improves when the patient lies down. These basic symptoms are often accompanied by fatigue, which is often worst after any type of exertion, along with a loss of concentration, blurred or tunnel vision, difficulty sleeping or nausea. POTS is considered a syndrome rather than a disease because it has many possible causes. It can be transient — a side effect of certain medications or a result of loss of conditioning, acute blood loss or dehydration — and in these cases it resolves when the trigger is removed. Other types of POTS are more persistent — which turned out to be the case for this patient — lasting months or years. © 2015 The New York Times Company
Link ID: 20575 - Posted: 02.13.2015
Madeline Bonin Bats and moths have been evolving to one-up each other for 65 million years. Many moths can hear bats’ ultrasonic echolocation calls, making it easy for the insects to avoid this predator. A few species of bat have developed echolocation calls that are outside the range of the moths’ hearing, making it harder for the moths to evade them1. But humans short-circuit this evolutionary arms race every time they turn on a porch light, according to a study in the Journal of Applied Ecology2. In field experiments, ecologist Corneile Minnaar of the University of Pretoria and his colleagues examined the diet of Cape serotine bats (Neoromicia capensis) both in the dark and under artificial light in a national park near Pretoria. The bat, an insect-eating species common in South Africa, has an echolocation call that moths can hear. Minnaar and his team determined both the species and quantity of available insect prey at the test sites using a hand-held net and a stationary trap. Cape serotine bats do not normally eat many moths. As the scientists expected, they caught more during the lighted trials than in the dark. What was surprising, however, was the discovery that the insects formed a greater share of the bats' diet during the lighted trials. The percentage of moths eaten in bright areas was six times larger than in dark zones, even though moths represented a smaller share of the total insect population under the lights than in the shade. But surprisingly, though moths represented a smaller share of the total insect population in the lighted areas, they played a larger role in the bats' diet. © 2015 Nature Publishing Group
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