By Neuroskeptic | Many people may be living life without a particular brain region – and not suffering any ill-effects. In a new paper in Neuron, neuroscientists Tali Weiss and colleagues discuss five women who appear to completely lack olfactory bulbs (OB). According to most neuroscience textbooks, no OB should mean no sense of smell, because the OB is believed to be a key relay point for olfactory signals. As Wikipedia puts it: The olfactory bulb transmits smell information from the nose to the brain, and is thus necessary for a proper sense of smell. Scent molecules activate olfactory receptors and signals travel up the olfactory nerves to the olfactory bulb, and then on to the rest of the brain via the olfactory tract. From Wikipedia. However, remarkably, Weiss et al.’s five women seem to have entirely normal sense of smell despite lacking any visible OBs on brain MRI scans. On both subjective and objective measures of olfactory function, these women showed no abnormalities. MRIs showing normal development of olfactory bulbs (A) compared to two women with no visible olfactory bulbs but normal sense of smell (B) & (D) and one woman with no sense of smell (C). From Weiss et al. Fig 1 Weiss et al. came across two of the women serendipitously while carrying out MRI scans for an unrelated project. The other 3 were found among healthy controls in the Human Connectome Project MRI dataset.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26825 - Posted: 11.18.2019

Hate eating certain vegetables? It could be down to your genes, say US scientists who have done some new research. Inheriting two copies of the unpleasant taste gene provides a "ruin-your-day level of bitterness" to foods like broccoli and sprouts, they say. It could explain why some people find it difficult to include enough vegetables in their diet, they suggest. The gene may also make beer, coffee and dark chocolate taste unpleasant. In evolutionary terms, being sensitive to bitter taste may be beneficial - protecting humans from eating things that could be poisonous. But Dr Jennifer Smith and colleagues from the University of Kentucky School of Medicine say it can also mean some people struggle to eat their recommended five-a-day of fresh fruit and veg. Everyone inherits two copies of a taste gene called TAS2R38. It encodes for a protein in the taste receptors on the tongue which allows us to taste bitterness. People who inherit two copies of a variant of the gene TAS2R38, called AVI, are not sensitive to bitter tastes from certain chemicals. Those with one copy of AVI and another called PAV perceive bitter tastes of these chemicals, but not to such an extreme degree as individuals with two copies of PAV, often called "super-tasters", who find the same foods exceptionally bitter. The scientists studied 175 people and found those with two copies of the bitter taste PAV version of the gene ate only small amounts of leafy green vegetables, which are good for the heart. Dr Smith told medics at a meeting of the American Heart Association: "You have to consider how things taste if you really want your patient to follow nutrition guidelines." © 2019 BBC.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26814 - Posted: 11.12.2019

By Veronique Greenwood When a bird preens its feathers, it uses a little of nature’s own pomade: an oil made by glands just above the tail. This oil helps clean and protect the bird’s plumage, but also contains a delicate bouquet of scents. To other birds — potential mates or would-be rivals — these smells carry many messages, not unlike the birdsongs and fancy feathers that are more obvious to human observers. These scents may signal that a bird would be dangerous to encounter or might be ready to mate, or any number of other cues. However, new research using dark-eyed juncos, a common North American bird, suggests that these odoriferous messages may not be entirely of the bird’s own making. In a study published last month in the Journal of Experimental Biology, biologists reported that microbes living peacefully on the birds’ oil glands may play an important role in making the scent molecules involved. That implies that the birds’ microbiomes may influence both the smell and the behavior it provokes in other birds. Birds’ scented messages are the focus of the research of Danielle Whittaker, managing director of the Beacon Center for the Study of Evolution in Action at Michigan State University and an author of the paper. Some years ago, after she gave a talk, Kevin Theis, a colleague who studied scent-producing bacteria living on hyenas and who is a co-author of the new paper, asked her whether she had ever looked at the birds’ microbes. “I had never thought about bacteria at all,” said Dr. Whittaker. “But all the compounds I was describing were known byproducts of bacterial metabolism.” Dr. Whittaker took samples of bacteria living on the oil glands of 10 captive dark-eyed juncos and then injected the glands with an antibiotic. When she compared the microbes before and after the treatment, the results seemed to show that two groups of bacteria in particular had taken a hit from the treatment. Furthermore, when she compared the scent molecules in the oil before and after the treatment, there were significant differences. © 2019 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 26812 - Posted: 11.11.2019

By Sofie Bates Some people may be able to smell even without key structures that relay odor information from the nose to the brain. Researchers used brain scans to identify two women who appear to be missing their olfactory bulbs, the only parts of the brain known to receive signals about smell sensations from the nose and send them to other parts of the brain for processing. Both individuals performed similarly to other women with olfactory bulbs on several tests to identify and differentiate odors, the scientists report November 6 in Neuron. The findings challenge conventional views of the olfactory system, and may lead to treatments for people with no sense of smell (SN: 7/2/07). “I’m not sure that our textbook view of how the [olfactory] system works is right,” says Noam Sobel, a neuroscientist at the Weizmann Institute of Science in Rehovot, Israel. MRI scans of the women’s brains revealed that where most people have two olfactory bulbs, these two appeared to have cerebrospinal fluid instead. To the researchers, this indicated that the women didn’t have olfactory bulbs. But Jay Gottfried, a neuroscientist at the University of Pennsylvania who was not involved in the study, says “I am not convinced that the women are indeed missing their bulbs.” Some evidence for olfactory bulbs may be undetectable with MRI, like microscopic structures or olfactory tissue that could be found with antibodies, he says. © Society for Science & the Public 2000–2019

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26800 - Posted: 11.07.2019

By Shraddha Chakradhar, Rockefeller University neuroscientist Vanessa Ruta was just named a member of the latest class of MacArthur “Genius” grant winners. The fellowship offers a five-year grant of $625,000 to individuals “who show exceptional creativity in their work and the prospect for still more in the future,” according to the MacArthur Foundation. Fortuitously, or perhaps by design, creativity has been a guiding principle for Ruta, 45, and her work. Both her parents were visual artists, and Ruta herself grew up as a ballet dancer—and at one point considered it a career path. After making the switch to science, however, she says that creativity—and the freedom that comes with it—still plays a big part in how she goes about her work. Her research now involves better understanding how the nervous system takes in external cues such as smell and processes these stimuli to inspire various behaviors. Advertisement STAT spoke with Ruta to learn more about her life and work. This interview has been lightly edited and condensed. Both your parents were artists. Did they influence how you work? I was strongly influenced by their creative process, which is parallel to how scientists work. There’s a kind of honing in your craft. It’s obvious in the artistic endeavors, whether it’s practicing dancing or something else. But it’s also there in the sciences—you have to be disciplined about pushing through with your experiments. © 2019 Scientific American

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26654 - Posted: 09.28.2019

Emily Makowski When we eat sour food, we instantaneously react due to a taste-sensing circuit between the tongue and the brain. Two papers published today (September 19)—one in Cell and the other in Current Biology—show that the otopetrin-1 proton channel in the tongue’s sour taste receptors is one of the components responsible for sour taste sensing in mice. These findings add to the body of sour taste research “from the molecular level, of how these protons are transported, up to the level of how the mice are able to taste it,” says Lucie Delemotte, a computational biophysicist at KTH Royal Institute of Technology who was not involved with either study. On the tongue, each taste bud contains a cluster of taste receptor cells innervated by a gustatory nerve network. The tips of these cells have a variety of taste molecule-capturing proteins and, in the case of sour detection, proteins that are called proton channels that sense pH. A team led by Charles Zuker at Columbia University Medical Center identified a potential sour taste receptor for the first time in 2006, and he and other researchers have continued to work on clarifying the mechanics and function of that receptor along with other possible sour taste receptors. A breakthrough occurred last year when Emily Liman of the University of Southern California’s lab discovered that otopetrin-1 (also referred to as OTOP1) was a proton channel also implicated in detecting sour tastes. But the researchers stopped short of demonstrating that OTOP1 was required for sour taste sensing in an actual animal—until now. © 1986–2019 The Scientist

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26631 - Posted: 09.21.2019

By Ryan P. Dalton Subject cDa29—well-known yet anonymous—resides somewhere in the north of England. You can almost see it: the peat stacks and old textile mills; the limestone and turf ruins where, on divine calling, Hadrian marked the northernmost reach of the Roman Empire. But even were you there, you wouldn’t see it the way cDa29 does. That’s because cDa29 is tetrachromatic: while most people see their world as a mix of three colors—red, green and blue—cDa29 sees hers in four. Difficult to imagine as that world may be for trichromats, your sense of smell provides access to an even richer world, one painted not in four colors but 400. You can almost smell it: the peat, the mills, the turf. How do your senses build these worlds? They begin with sensory “receptors,” which sit on the surfaces of cells and are activated by specific stimuli. In the case of vision, there are three color photoreceptors in your retina—activated by red, green or blue light. By keeping these receptors separated—such that no two photoreceptors occur together in one cell—your retina can keep track of what colors came from where. As a counterexample, you have a few dozen “bitter receptors” on your tongue, but each bitter taste cell contains several of them. This arrangement allows you to detect many different bitter compounds, but it does not help you distinguish between them. As these examples illustrate, you must both be able to detect a wide range of stimuli and to discriminate between those stimuli—and generally, your senses strike a balance between these two objectives. Ever the romantic, your sense of smell casts aside the suggestion of balance and optimizes for both detection and discrimination. Olfactory neurons in your nose have evolved some 400 odor receptors, and each neuron contains only one. Receptors are tuned to detect a few basic odors apiece: some detect geranium petals or pine needles, while others detect the by-products of putrefaction. To organize all this information, your olfactory neurons wire into an “olfactory map” on your brain’s olfactory bulb. Olfactory neurons are one of the few types of neurons that are born throughout your life, and each of the roughly 10,000 such neurons born each day in your nose subsequently wires into the olfactory map in your brain. © 2019 Scientific American

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26492 - Posted: 08.13.2019

Sacha Pfeiffer There's a new smell tingling tourists' noses in the Big Apple, far above the trash bag-lined sidewalks — and this scent is by design. Atop One World Trade Center, New York City's tallest building, a fragrance carrying hints of citrus, beech trees and red maples wafts through the glass-enclosed observatory deck. When the observatory commissioned the custom scent to diffuse through the floor's HVAC system, Managing Director Keith Douglas told the New York Times that he wanted it to elicit a "positive thought," and offer a "a subtle complement to the experience" of visiting the space. But not everyone is keen on the scent. One tourist described the smell as "sickly," according to the Times, which first documented the new aromatic experience in lower Manhattan. It's a marketing strategy businesses are increasingly deploying to lure customers into stores and entice them to stay longer. The smell of cinnamon fills Yankee Candle stores, Subway pumps a doughy bread scent through its vents. International Flavors & Fragrances, the same company that developed clothing chain Abercrombie & Fitch's notoriously pungent "Fierce" cologne, known to linger on clothes long after their purchase, designed One World's scent. "The quickest way to change somebody's mood or behavior is with smell," says Dr. Alan Hirsch, neurological director of the Smell and Taste Treatment and Research Foundation in Chicago. © 2019 npr

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 11: Emotions, Aggression, and Stress
Link ID: 26487 - Posted: 08.12.2019

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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 4: Development of the Brain
Link ID: 26285 - Posted: 06.01.2019

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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 14: Attention and Higher Cognition
Link ID: 26203 - Posted: 05.03.2019

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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 5: The Sensorimotor System
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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26144 - Posted: 04.16.2019

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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26062 - Posted: 03.22.2019

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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 11: Emotions, Aggression, and Stress
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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
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.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 13: Memory and Learning
Link ID: 25963 - Posted: 02.14.2019

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

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 25891 - Posted: 01.22.2019