Chapter 9. Hearing, Vestibular Perception, Taste, and Smell

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By Virginia Morell Most of us can look at two meal plates and easily tell which one has more food on it. But if someone turns out the lights, we’re out of luck. Not so for Asian elephants. A new study reveals that the pachyderms can judge food quantity merely by using their sense of smell, the first time an animal has been shown to do this. To conduct the research, scientists presented six Asian elephants (Elephas maximus) at an educational sanctuary in Thailand with two opaque, locked buckets containing 11 different ratios of sunflower seeds, a favorite treat. The elephants could not see how many seeds each bucket contained, but they could smell the contents through small holes in the lids. The animals chose the bucket with the greater quantity of food 59% to 82% of the time, the team reports today in the Proceedings of the National Academy of Sciences. (Even dogs, with their famed sense of smell, fail this test, other research has shown.) The discovery makes sense, the scientists say, because elephants are known to have the highest number of genes associated with olfactory reception of any species (about 2000 versus dogs’ 811). They can distinguish between the scent of Maasai pastoralists and Kamba farmers, and rely on their sense of smell to navigate long distances to find food and water (up to 19.2 kilometers). The researchers hope their findings could help mitigate human-elephant conflicts in Asia and Africa, because wandering herds use odors to decide where to travel; enticing scents might help lure them away from agricultural fields, for instance. © 2019 American Association for the Advancement of Science

Keyword: Chemical Senses (Smell & Taste)
Link ID: 26293 - Posted: 06.04.2019

Kerry Grens In mice whose sense of smell has been disabled, a squirt of stem cells into the nose can restore olfaction, researchers report today (May 30) in Stem Cell Reports. The introduced “globose basal cells,” which are precursors to smell-sensing neurons, engrafted in the nose, matured into nerve cells, and sent axons to the mice’s olfactory bulbs in the brain. “We were a bit surprised to find that cells could engraft fairly robustly with a simple nose drop delivery,” senior author Bradley Goldstein of the University of Miami Miller School of Medicine says in a press release. “To be potentially useful in humans, the main hurdle would be to identify a source of cells capable of engrafting, differentiating into olfactory neurons, and properly connecting to the olfactory bulbs of the brain. Further, one would need to define what clinical situations might be appropriate, rather than the animal model of acute olfactory injury.” Goldstein and others have independently tried stem cell therapies to restore olfaction in animals previously, but he and his coauthors note in their study that it’s been difficult to determine whether the regained function came from the transplant or from endogenous repair stimulated by the experimental injury to induce a loss of olfaction. So his team developed a mouse whose resident globose basal cells only made nonfunctional neurons, and any restoration of smell would be attributed to the introduced cells. © 1986–2019 The Scientist

Keyword: Chemical Senses (Smell & Taste); Stem Cells
Link ID: 26285 - Posted: 06.01.2019

Hannah Devlin Science correspondent A mind-controlled hearing aid that allows the wearer to focus on particular voices has been created by scientists, who say it could transform the ability of those with hearing impairments to cope with noisy environments. The device mimics the brain’s natural ability to single out and amplify one voice against background conversation. Until now, even the most advanced hearing aids work by boosting all voices at once, which can be experienced as a cacophony of sound for the wearer, especially in crowded environments. Nima Mesgarani, who led the latest advance at Columbia University in New York, said: “The brain area that processes sound is extraordinarily sensitive and powerful. It can amplify one voice over others, seemingly effortlessly, while today’s hearing aids still pale in comparison.” This can severely hinder a wearer’s ability to join in conversations, making busy social occasions particularly challenging. Scientists have been working for years to resolve this problem, known as the cocktail party effect. The brain-controlled hearing aid appears to have cracked the problem using a combination of artificial intelligence and sensors designed to monitor the listener’s brain activity. The hearing aid first uses an algorithm to automatically separate the voices of multiple speakers. It then compares these audio tracks to the brain activity of the listener. Previous work by Mesgarani’s lab found that it is possible to identify which person someone is paying attention to, as their brain activity tracks the sound waves of that voice most closely. © 2019 Guardian News & Media Limited

Keyword: Hearing
Link ID: 26247 - Posted: 05.18.2019

By Maggie Koerth-Baker Where is the loudest place in America? You might think New York City, or a major airport hub, or a concert you have suddenly become too old to appreciate. But that depends on what kind of noise you’re measuring. Sound is actually a physical thing. What we perceive as noise is the result of air molecules bumping into one another, like a Newton’s cradle toy. That movement eventually reaches our eardrums, which turn that tiny wiggle into an audible signal. But human ears can’t convert all molecular motion to sound. Sometimes the particles are jostling one another too fast. Sometimes they’re too slow. Sometimes, the motion is just happening in the wrong medium — through the Earth, say, instead of through the air. And when you start listening for the sounds we can’t hear, the loudest place in America can end up being right under your feet. Scientists have tools that can detect these “silent” waves, and they’ve found a lot of noise happening all over the U.S. Those noises are made by the cracking of rocks deep in the Earth along natural fault lines and the splashing of whitecaps on the ocean. But they’re also made by our factories, power plants, mines and military. “Any kind of mechanical process is going to generate energetic waves, said Omar Marcillo, staff scientist at Los Alamos National Laboratory. “Some of that goes through the atmosphere as acoustic waves, and some goes through the ground as seismic waves.” Marcillo’s work focuses on the seismic. © 2019 ABC News Internet Ventures.

Keyword: Hearing
Link ID: 26227 - Posted: 05.11.2019

By Heather Murphy The scent of lily of the valley cannot be easily bottled. For decades companies that make soap, lotions and perfumes have relied on a chemical called bourgeonal to imbue their products with the sweet smell of the little white flowers. A tiny drop can be extraordinarily intense. If you can smell it at all, that is. For a small percentage of people, it fails to register as anything. Similarly, the earthy compound 2-ethylfenchol, present in beets, is so powerful for some people that a small chunk of the root vegetable smells like a heap of dirt. For others, that same compound is as undetectable as the scent of bottled water. These — and dozens of other differences in scent perception — are detailed in a new study, published this week in the journal PNAS. The work provides new evidence of how extraordinarily different one person’s “smellscape” may be from another’s. It’s not that some people are generally better smellers, like someone else may have better eyesight, it’s that any one person might experience certain scents more intensely than their peers. “We’re all smelling things a little bit differently,” said Steven Munger, director of The Center for Smell and Taste at the University of Florida, who was not involved in the study. The scientists who conducted the study looked for patterns in subjects’ genetic code that could explain these olfactory differences. They were surprised to find that a single genetic mutation was linked to differences in perception of the lily of the valley scent, beet’s earthiness, the intensity of whiskey’s smokiness along with dozens of other scents. “I think it’s a very important finding,” said Stavros Lomvardas, a neuroscientist at Columbia University’s Zuckerman Institute, who was not involved in the research either. The study was conducted in a large room at Rockefeller University in New York City. Around 300 subjects were invited to sit in front of a computer screen surrounded by 150 jars of assorted odors. The screen alerted them to which jar sniff at any given time, and they then rated the intensity of each on a scale from 1 (extremely weak) to 7 (extremely strong) and pleasantness from 1 (extremely unpleasant) to 7 (extremely pleasant). © 2019 The New York Times Company

Keyword: Chemical Senses (Smell & Taste); Genes & Behavior
Link ID: 26203 - Posted: 05.03.2019

Nicola Davis Olfactory tests could help doctors spot older adults who are at greater risk of developing dementia, researchers say. The sense of smell is known to deteriorate with age. However, researchers have previously found it might also hint at health problems: older adults who struggle to identify odours have a greater chance of dying in the near future regardless of how old they are. Other studies have found older adults who have difficulties in identifying and remembering smells are more likely to have characteristics linked to a greater risk of developing Alzheimer’s disease even if there is no current sign of cognitive decline. Get Society Weekly: our newsletter for public service professionals Read more It is thought the sense of smell is one of the first faculties affected by certain neurodegenerative diseases. Now experts say they have probed further, and those diseases alone do not explain why a poor sense of smell might bode ill. “My suspicion is [the] process of smell in older adults probably has much broader potential health implications than what we already know about,” said Prof Honglei Chen, a co-author of the research from Michigan State University. He suggested it could be linked to conditions of the immune system and even psychiatric disorders. © 2019 Guardian News & Media Limited

Keyword: Alzheimers; Chemical Senses (Smell & Taste)
Link ID: 26184 - Posted: 04.30.2019

Lisa Wehrstedt Researchers in Philadelphia revealed last week that tastebuds also bear odour-detecting proteins, calling into question the idea that smell and taste come together in the brain to produce flavour. According to Dr Mehmet Hakan Ozdener, his findings open up the possibility of using smells to trick us into healthier eating, for example by adding a low-concentration odour to food to make it taste sweeter and thereby reduce sugar intake. It is believed that we all experience a form of motion-induced blindness while driving at night, when the red lights of the cars in front temporarily disappear if we move our eyes to the oncoming traffic. This phenomenon, where the brain ignores or discards visual information when it is placed in front of a moving background, was first observed in the lab in 1965. First described in 1976, the McGurk effect is a connection between hearing and vision in speech perception. When the auditory component of a syllable is paired with the visual component of another, this can lead to the perception of a third sound. Research conducted by the University of Oxford in 2013 suggests that the sight of cutlery and the perception of its size, weight, shape and colour have an effect on how we determine flavour, suggesting that the brain makes judgments on food even before it goes in our mouths. Yoghurt, for example, tastes sweeter on a white spoon than it does on a black spoon. © 2019 Guardian News & Media Limited

Keyword: Chemical Senses (Smell & Taste); Vision
Link ID: 26180 - Posted: 04.29.2019

By C. Claiborne Ray Q. Our dog escaped from the car. How did he find his way home the next day from nearly three miles away? A. What took so long? Dogs are well known for their ability to backtrack to a beloved home — or person. Most animal behavior experts attribute their navigating ability largely to a hypersensitive sense of smell. Three miles is not a great distance, compared with some of the epic homeward journeys that dogs have occasionally made, and a three-mile radius would be rich in odor guideposts. The theory is that a dog creates a map of scents from odiferous sites like a food store or fertilized garden — or even just a hint of an owner’s scent in the ground or air. Dogs are especially sensitive to the odor of the humans in their lives. One study used MRI imaging to study activity in the caudate nucleus, a brain area associated with the expectation of a reward. Dogs of varying breeds were exposed to their own scent or that of a familiar dog, a strange dog, a strange human or a familiar human. By far the strongest activation followed exposure to the scent of a familiar person. Another navigational clue may come from dogs’ suspected sensitivity to differences in magnetic orientation. A study of dozens of dogs found that they usually preferred to defecate with their bodies aligned in a north-south orientation, a preference that disappeared when the magnetic field was disturbed. © 2019 The New York Times Company

Keyword: Chemical Senses (Smell & Taste)
Link ID: 26144 - Posted: 04.16.2019

/ By Jed Gottlieb In 1983, The New York Times published a bombshell report about President Ronald Reagan: Starkey Laboratories had fitted the President, then 72, with a hearing aid. The news was welcomed by health professionals who reckoned it could help to reduce the stigma associated with hearing loss. At the time, one in three people over the age of 60 was thought to have hearing problems, though only around 20 percent who needed hearing aids used them. “The way I do the math, a third of all adults have unaddressed hearing issues. That’s lot of people.” Indeed, Reagan’s handlers knew too well that the revelation risked making the president look like a feeble old man — and worse, someone ill-equipped to run the most powerful nation on earth. “Among Presidential advisers,” The New York Times noted, “Mr. Reagan’s use of a hearing aid revived speculation on whether his age would be an issue if he seeks re-election next year.” Reagan won re-election, of course, but nearly 40 years later, negative perceptions persist — and health advocates are more concerned than ever. Hearing loss, they say, is not just a functional disability affecting a subset of aging adults. With population growth and a boom in the global elderly population, the World Health Organization (WHO) now estimates that by 2050, more than 900 million people will have disabling hearing loss. A 2018 study of 3,316 children aged nine to 11 meanwhile, found that 14 percent already had signs of hearing loss themselves. While not conclusive, the study linked the loss to the rise of portable music players. Copyright 2019 Undark

Keyword: Hearing
Link ID: 26124 - Posted: 04.09.2019

By Jamie Lauren Keiles When Jennifer Allen watched videos of space, she sometimes felt this peculiar sensation: a tingling that spread through her scalp as the camera pulled back to show the marble of the earth. It came in a wave, like a warm effervescence, making its way down the length of her spine and leaving behind a sense of gratitude and wholeness. Allen loved this feeling, but she didn’t know what caused it. It was totally distinct from anything she’d experienced before. Every two years or so she’d take to Google. She tried searching things like “tingling head and spine” or “brain orgasm.” For nine years, the search didn’t turn up anything. Then, around 2009, it did. As always, Allen typed her phrases into Google, but this time she got a result on a message board called SteadyHealth. The post was titled WEIRD SENSATION FEELS GOOD: i get this sensation sometimes. theres no real trigger for it. it just happens randomly. its been happening since i was a kid and i’m 21 now. some examples of what it seems has caused it to happen before are as a child while watching a puppet show and when i was being read a story to. as a teenager when a classmate did me a favor and when a friend drew on the palm of my hand with markers. sometimes it happens for no reason at all The poster went on to demand an explanation. In the discussion, nobody had one, but many described a similar feeling — a “silvery sparkle” inside the head, a euphoric “brain-gasm” or a feeling like goose bumps in the scalp that faded “in and out in waves of heightened intensity.” Many people agreed that the sensation was euphoric. (“Aside from an actual orgasm, it’s probably the most enjoyable sensation possible,” one user wrote.) Its triggers were as varied as watching someone fill out a form, listening to whispering sounds or seeing Bob Ross paint landscapes on TV. Allen scrolled through pages and pages of discussion. Oh my gosh, she remembers thinking. These people are talking about exactly what I experience. © 2019 The New York Times Company

Keyword: Pain & Touch; Hearing
Link ID: 26114 - Posted: 04.04.2019

Nell Greenfieldboyce Mosquitoes searching for a meal of blood use a variety of clues to track down humans, including our body heat and the carbon dioxide in our breath. Now, research shows that a certain olfactory receptor in their antennae also serves as a detector of humans, responding to smelly chemicals in our sweat. Targeting this receptor might offer a new way to foil blood-seeking mosquitoes and prevent the transmission of diseases including malaria, Zika virus and dengue, according to the study published Thursday in the journal Current Biology. "We found a receptor for human sweat, and we found that acidic volatiles that come off of us are really key for mosquitoes to find us," says Matthew DeGennaro, a neurogeneticist at Florida International University in Miami. "I think what's exciting about it is that finally we have evidence that there is some sort of pathway, in the sense of smell, that is required for mosquitoes to like us," says Lindy McBride, a scientist at Princeton University who studies mosquito behavior and was not part of the research team. It's long been known that mosquitoes rely on multiple clues to target humans. First, a mosquito will sense exhaled carbon dioxide from a distance that can be more than 30 feet. "After the carbon dioxide," DeGennaro explains, "then it begins to sense human odor." © 2019 npr

Keyword: Chemical Senses (Smell & Taste)
Link ID: 26092 - Posted: 03.29.2019

By James Gallagher Health and science correspondent, BBC News French scientists say they have proof that dogs can pick up the smell of an epileptic seizure. The University of Rennes team hope the findings could lead to ways to predict when people will have a seizure. These could include dogs or "electronic noses" that pick up the precise odour being given off during a seizure. Dogs have previously been shown to be able to sniff out diseases including cancers, Parkinson's, malaria and diabetes. Some people with epilepsy already rely on the animals. One sleeping in a child's bedroom can alert family members of a seizure in the middle of the night. The latest study, in the journal Scientific Reports, trained five dogs from Medical Mutts, in the US, to recognise the smell of sweat taken from a patient having a seizure. They were then given a choice of seven sweat samples taken from other patients while they were either relaxing, exercising or having a seizure. Two of the dogs found the seizure sample about two-thirds of the time and the other three were 100% accurate The report says: "The results are extremely clear and constitute a first step towards identifying a seizure-specific odour." © 2019 BBC

Keyword: Chemical Senses (Smell & Taste); Epilepsy
Link ID: 26091 - Posted: 03.29.2019

By Richard Klasco, M.D. Q. I have completely lost my sense of smell and can taste only a few things. I have seen doctors and taken tests, but no answers. I know I’m not the only one with this problem. Any ideas? A. Humans are able to perceive an astounding one trillion odors. But our sense of smell is fragile. About a quarter of adults, and more than half of those over 80, have some degree of olfactory impairment. The sense of taste is often affected at the same time, as the neural pathways of smell and taste commingle in the brain. Having an impaired sense of smell may be more than a nuisance. Studies have linked a decreased sense of smell to a heightened risk for Parkinson’s disease, Alzheimer’s disease, multiple sclerosis and premature death. Common causes of a decreased sense of smell include nasal problems, such as deviated septum and nasal polyps; viruses, such as rhinovirus and Epstein-Barr virus; chronic sinusitis; head injury; and certain cancers. Environmental exposure to cigarette smoke, alcohol, air pollution and toxins further increase the risk. Yet, in about 16 percent of people, no cause can be identified. Eating nuts and fish has been associated with protection against smell impairment, as have exercise and use of cholesterol-lowering drugs and oral steroids. It is unknown, however, whether changing one’s dietary or exercise habits will improve the sense of smell. Medical evaluation typically begins with an otolaryngologist, an ear, nose and throat doctor who will use a standardized scratch-and-sniff test to assess any olfactory deficits. Laboratory tests of blood and nasal mucus and imaging studies, such as CT or M.R.I. scans, are often needed. In some cases, endoscopic surgery, a flexible camera inserted into the nose, may aid in diagnosis and provide therapeutic benefits. © 2019 The New York Times Company

Keyword: Chemical Senses (Smell & Taste)
Link ID: 26062 - Posted: 03.22.2019

Ian Sample Science editor Scientists have developed a test for Parkinson’s disease based on its signature odour after teaming up with a woman who can smell the condition before tremors and other clinical symptoms appear. The test could help doctors diagnose patients sooner and identify those in the earliest stages of the disease, who could benefit from experimental drugs that aim to protect brain cells from being killed off. Perdita Barran, of the University of Manchester, said the test had the potential to decrease the time it took to distinguish people with normal brain ageing from those with the first signs of the disorder. “Being able to say categorically, and early on, that a person has Parkinson’s disease would be very useful,” she said. Get Society Weekly: our newsletter for public service professionals Read more Most people cannot detect the scent of Parkinson’s, but some who have a heightened sense of smell report a distinctive, musky odour on patients. One such “super smeller” is Joy Milne, a former nurse, who first noticed the smell on her husband, Les, 12 years before he was diagnosed. Milne only realised she could sniff out Parkinson’s when she attended a patient support group with her husband and found everyone in the room smelled the same. She thought little more about it until she mentioned the odour to Tilo Kunath, a neurobiologist who studies Parkinson’s at Edinburgh University. © 2019 Guardian News & Media Limited

Keyword: Parkinsons; Chemical Senses (Smell & Taste)
Link ID: 26056 - Posted: 03.20.2019

Maria Temming A new analysis of people’s brain waves when surrounded by different magnetic fields suggests that people have a “sixth sense” for magnetism. Birds, fish and some other creatures can sense Earth’s magnetic field and use it for navigation (SN: 6/14/14, p. 10). Scientists have long wondered whether humans, too, boast this kind of magnetoreception. Now, by exposing people to an Earth-strength magnetic field pointed in different directions in the lab, researchers from the United States and Japan have discovered distinct brain wave patterns that occur in response to rotating the field in a certain way. These findings, reported in a study published online March 18 in eNeuro, offer evidence that people do subconsciously respond to Earth’s magnetic field — although it’s not yet clear exactly why or how our brains use this information. “The first impression when I read the [study] was like, ‘Wow, I cannot believe it!’” says Can Xie, a biophysicist at Peking University in Beijing. Previous tests of human magnetoreception have yielded inconclusive results. This new evidence “is one step forward for the magnetoreception field and probably a big step for the human magnetic sense,” he says. “I do hope we can see replications and further investigations in the near future.” During the experiment, 26 participants each sat with their eyes closed in a dark, quiet chamber lined with electrical coils. These coils manipulated the magnetic field inside the chamber such that it remained the same strength as Earth’s natural field but could be pointed in any direction. Participants wore an EEG cap that recorded the electrical activity of their brains while the surrounding magnetic field rotated in various directions. |© Society for Science & the Public 2000 - 2019

Keyword: Pain & Touch
Link ID: 26052 - Posted: 03.19.2019

Tina Hesman Saey BALTIMORE — Some police dogs may smell fear, and that could be bad news for finding missing people whose genetic makeup leaves them more prone to stress. Trained police dogs couldn’t recognize stressed-out people with a particular version of a gene that’s involved in stress management, geneticist Francesco Sessa reported February 22 at the annual meeting of the American Academy of Forensic Sciences. The dogs had no trouble identifying the men and women volunteers when the people weren’t under stress. The study may help explain why dogs can perform flawlessly in training, but have difficulty tracking people in real-world situations. Sessa, of the University of Foggia in Italy, and colleagues wondered whether fear could change a person’s normal scent and throw off dogs’ ability to find missing people. The researchers also investigated whether people’s genes might make some individuals easier or harder for dogs to pick out of a lineup. Previous studies already had linked different versions of the serotonin transporter gene SLC6A4 to stress management. People with the long version of the gene tend to handle stress better than people with the short version, Sessa said. He and colleagues recruited four volunteers — a man and a woman who each have the long version of the gene and a man and a woman with the short version. Each of the participants wore a scarf for a couple of hours a day to imprint their scent on the garment. Then the researchers brought the volunteers into the lab. In the first session, the volunteers wore a T-shirt and weren’t subjected to any stressors. The team then created two lineups of T-shirts, one with those of the men and another for the women. After sniffing the scarves, two trained police dogs had no trouble identifying any of the volunteers in a lineup of 10 T-shirts. The canine units identified each of the volunteers in three out of three attempts. |© Society for Science & the Public 2000 - 2019

Keyword: Chemical Senses (Smell & Taste); Genes & Behavior
Link ID: 25993 - Posted: 02.28.2019

Laura Sanders Sometimes a really good meal can make an evening unforgettable. A new study of rats, published online February 18 in the Journal of Neuroscience, may help explain why. A select group of nerve cells in rats’ brains holds information about both flavors and places, becoming active when the right taste hits the tongue when the rat is in a certain location. These double-duty cells could help animals overlay food locations onto their mental maps. Researchers implanted electrodes into the hippocampus, an area of the brain that is heavily involved in both memory formation and mapping. The rats then wandered around an enclosure, allowing researchers to identify “place cells” that become active only when the rat wandered into a certain spot. At the same time, researchers occasionally delivered one of four flavors (sweet, salty, bitter and plain water) via an implanted tube directly onto the wandering rats’ tongues. Some of the active place cells also responded to one or more flavors, but only when the rat was in the right spot within its enclosure. When the rat moved away from a place cell’s preferred spot, that cell no longer responded to the flavor, the researchers found. A mental map of the best spots for tasting something good would come in handy for an animal that needs to find its next meal. Citations L.E. Herzog et al. Interaction of taste and place coding in the hippocampus. Journal of Neuroscience. Published online February 18, 2019. doi: 10.1523/JNEUROSCI.2478-18.2019. |© Society for Science & the Public 2000 - 2019

Keyword: Chemical Senses (Smell & Taste)
Link ID: 25973 - Posted: 02.19.2019

Shawna Williams Watch a bacterium chase down the source of an enticing molecular trail using chemo-taxis, and it’s clear that its sensory and navigation abilities are tightly linked. But could the same be true for humans? In 2014, Louisa Dahmani, then a graduate student at McGill University in Montreal, set out to answer that question. After having reviewed the literature on studies of spatial memory and olfaction in people, “I realized that the two functions seemed to rely on similar brain regions,” she explains. “But no one had actually looked at it directly and tested the same sample of participants on an olfaction and on a spatial memory task.” Dahmani, her advisor Véronique Bohbot, and their colleagues set out to rectify that. The group recruited 60 volunteers and tested their ability to identify 40 odors, from menthol to cucumber to lavender. The researchers also had the subjects do a computer-based task in which they moved through a virtual town. After their exploration, the subjects navigated through the virtual town from one of its eight landmarks to a different destination via the shortest route possible. “People who are better at finding their way are also better at identifying smells,” Dahmani says, summing up the study’s biggest takeaway. The scientists also imaged participants’ brains using MRI and found that a larger medial orbitofrontal cortex—a brain region known to be associated, along with the hippocampus, with spatial navigation—correlated with both better smell identification and fewer errors on the navigation task (Nat Comm, 9:4162, 2018). © 1986 - 2019 The Scientist.

Keyword: Chemical Senses (Smell & Taste); Learning & Memory
Link ID: 25963 - Posted: 02.14.2019

Emily Conover Lasers can send sounds straight to a listener’s ear, like whispering a secret from afar. Using a laser tuned to interact with water vapor in the air, scientists created sounds in a localized spot that were loud enough to be picked up by human hearing if aimed near a listener’s ear. It’s the first time such a technique can be used safely around humans, scientists from MIT Lincoln Laboratory in Lexington, Mass., report in the Feb. 1 Optics Letters. At the wavelengths and intensities used, the laser won’t cause burns if it grazes eyes or skin. The scientists tested out the setup on themselves in the laboratory, putting their ears near the beam to pick up the sound. “You move your head around, and there’s a couple-inch zone where you go ‘Oh, there it is!’… It’s pretty cool,” says physicist Charles Wynn. The researchers also used microphones to capture and analyze the sounds. The work relies on a phenomenon called the photoacoustic effect, in which pulses of light are converted into sound when absorbed by a material, in this case, water vapor. Based on this effect, the researchers used two different techniques to make the sounds. The first technique, which involves rapidly ramping the intensity of the laser beam up and down, can transmit voices and songs. “You can hear the music really well; you can understand what people are saying,” says physicist Ryan Sullenberger, who coauthored the study along with Wynn and physicist Sumanth Kaushik. |© Society for Science & the Public 2000 - 2019.

Keyword: Hearing
Link ID: 25925 - Posted: 02.02.2019

By James Gorman Carpenter ants follow trails. Just watch them wandering about on your wooden porch until they strike a trail of pheromones (chemicals ants use for communication) that another ant has laid down. Ants don’t have noses, so they wave their antennas around to pick up the trail, then off they go on the road to ruin. (Carpenter ants destroy houses.) Scientists know plenty about ants, including their ability to follow scent trails, but researchers at Harvard wanted to get a more detailed understanding of how exactly ants sniff, or taste, the pheromone-marked path. First, some basics: Ants use their antennas to pick up chemical cues left by other ants. And the chemical sense of ants, call it smell or taste or chemo-reception, enables them to follow straight trails, curved trails, even zigzags. To see how ants do it, the scientists mixed ink and ant pheromones and used the result to paint trails on paper. They set ants out on trails and recorded dozens of hours of ant movement. They analyzed the video and tried out different computer models of the ants’ behavior. What Ryan W. Dash and his adviser, Venkatesh N. Murthy, and other researchers found was that the ants had several strategies for path-following. The scientists published their results in the Journal of Experimental Biology. All the ants used their antennas to sweep the trail side to side. One strategy they used was probing. A probing ant moved slowly, keeping its antennas close together. The researchers termed another strategy exploratory: Ants still moved slowly, but they took winding paths moving away from and back to a trail. When they were locked into a pheromone trail, they moved along more quickly, keeping their antennas on either side of the path. They kept one antenna closer to the path, but which antenna varied from ant to ant. In other words, some were lefties and others were righties. © 2019 The New York Times Company

Keyword: Chemical Senses (Smell & Taste)
Link ID: 25891 - Posted: 01.22.2019