By Katharine Gammon Picture this: You’re sitting down, engrossed in a meal, when an unfamiliar person walks by. There’s something about them—Hair? Smile? Vibes?—that instantly draws you in and makes you want to strike up a friendship. A new study suggests that it could be the scent they exude that attracts you to them. Not just the way their skin or hair smells, but the deodorant and shampoo they use, the foods they consume, even their laundry detergent. Our sense of smell tends to operate below the level of conscious awareness, says Jessica Gaby, a psychology researcher at Middle Tennessee State University and an author of the study, so our responses to it are often hidden from us. “But at the same time, it’s inescapable,” she says. “You can’t fake it.” Gaby and her colleagues, who were at Cornell University when the study was conducted, brought 40 women aged 18-30 together in a Cornell dining hall, a large, refurbished barn with café tables that doubles as a beer hall at night. The scent of popcorn, beer, and leftover dinner wafted over the room: The idea was to have a complex olfactory environment. The women all identified as heterosexual, so the researchers could focus on the type of attraction that might lead to friendship. In the first phase of the study, the participants received cotton T-shirts and were instructed to wear them for 12 hours straight without altering their daily routines, and to keep notes about their activities. One participant used spray paint in an art project, another had sex, another said she spilled a small amount of black beans on her shirt. In the second phase of the study, the participants were instructed to view photographs of different individual women, some of whom they would later meet. They then each sniffed the worn T-shirts, then had four-minute meetings, speed-dating style, with the other individual women, then sniffed their T-shirts again. After each step, they judged their friendship potential with the other women on a scale of 1 to 7. © 2025 NautilusNext Inc.,

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: 29783 - Posted: 05.11.2025

Andrew Gregory Health editor Doctors in London have successfully restored a sense of smell and taste in patients who lost it due to long Covid with pioneering surgery that expands their nasal airways to kickstart their recovery. Most patients diagnosed with Covid-19 recover fully. But the infectious disease can lead to serious long-term effects. About six in every 100 people who get Covid develop long Covid, with millions of people affected globally, according to the World Health Organization. Losing a sense of smell and taste are among more than 200 different symptoms reported by people with long Covid. Now surgeons at University College London Hospitals NHS Foundation Trust (UCLH) have cured a dozen patients, each of whom had suffered a profound loss of smell after a Covid infection. All had experienced the problem for more than two years and other treatments, such as smell training and corticosteroids, had failed. In a study aiming to find new ways to resolve the issue, surgeons tried a technique called functional septorhinoplasty (fSRP), which is typically used to correct any deviation of the nasal septum, increasing the size of nasal passageways. This boosts airflow into the olfactory region, at the roof of the nasal cavity, which controls smell. Doctors said the surgery enabled an increased amount of odorants – chemical compounds that have a smell – to reach the roof of the nose, where sense of smell is located. They believe that increasing the delivery of odorants to this area “kickstarts” smell recovery in patients who have lost their sense of smell to long Covid. © 2025 Guardian News & Media Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29697 - Posted: 03.08.2025

By Bethany Brookshire Self-awareness may be beyond primates in the wild. Chimps, organutans and other species faced with a mirror react to a dot on their face in the lab, a widely used measure of self-awareness. But while baboons in Namibia exposed to mirrors find the reflective glass fascinating, they don’t respond to dots placed on their faces, researchers report in the January Proceedings of the Royal Society B: Biological Sciences. The result could indicate that lab responses to mirrors are a result of training — and that self-awareness might exist on a spectrum. Support Science Today. Thank you for being a subscriber to Science News! Interested in more ways to support STEM? Consider making a gift to our nonprofit publisher, the Society for Science, an organization dedicated to expanding scientific literacy and ensuring that every young person can strive to become an engineer or scientist. Donate Now “Psychological self-awareness is this idea that you as an individual can become an object of your own attention,” says Alecia Carter, an evolutionary anthropologist at University College London. It’s a hard concept to measure in other species, in part, she notes, because “it’s also difficult to imagine not having that kind of self-awareness.” One measure of self-awareness is the mark test. An animal sits in front of a mirror, and a mark is placed somewhere they normally cannot see, such as on the face. If the animal recognizes themselves in the mirror, and the mark as out of place, the animal will respond to the mark. Chimps, orangutans and bonobos have “passed” the mark test in the lab, while primates that are not great apes, such as rhesus macaques, have mastered it only after training. Other species, such as Asian elephants, dolphins and even a fish called the cleaner wrasse, have also responded to the mark test. © Society for Science & the Public 2000–2025.

Related chapters from BN: Chapter 18: Attention and Higher Cognition; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 14: Attention and Higher Cognition
Link ID: 29654 - Posted: 02.01.2025

By Jackson Ryan Fruit fly larvae can sense the texture of rotting fruit.Credit: Scott Bauer/USDA/SPL For maggots, the experience of eating a succulent meal isn’t just about how their food tastes, but also how it feels. Researchers used genetic tools to reveal that certain neurons in the brain control food choice and can sense both taste and texture1 . The conventional view of taste sensing holds that specific neurons carry single signals to the brain, says study co-author Simon Sprecher, a neurobiologist at the University of Fribourg in Switzerland. For instance, sweet taste neurons carry sweet signals and bitter taste neurons carry bitter signals. But those assumptions have been challenged over the past two decades by studies in fruit flies and mice that suggest neurons might have the capacity to respond to both chemical signals, such as bitter or sweet, as well as mechanical signals, such as texture. In the current study, published in PLoS Biology on 30 January, Sprecher and his colleagues set out to see whether individual neurons in taste organs have this ‘multimodal’ capacity. They fed fruit-fly larvae — maggots — different preparations of agarose, a sugary gel. The maggots showed a propensity for a ‘Goldilocks’ preparation, one that was neither too hard nor too soft. The preferred hardness for larvae is “similar to [that] of decaying fruit”, says Sprecher. The researchers then used genetic engineering tools to disable a subset of taste-sensing neurons in the larval taste-sensing organs. Disabling the neurons prevented the maggots from tasting the sweetness of the agarose, as expected, but it also changed which preparations they ate — the maggots no longer preferred Goldilocks preparations, suggesting that they had also lost their ability to feel their food. By studying individual neurons, the researchers determined that C6 neurons can both taste sugar and sense mechanical simulation. © 2025 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29650 - Posted: 02.01.2025

Nicola Davis Science correspondent The human sense of smell is nothing to turn one’s nose up at, research suggests, with scientists revealing we are far more sensitive to the order of odours captured by a sniff than previously thought. Charles Darwin is among those who have cast aspersions on our sense of smell, suggesting it to be “of extremely slight service” to humans, while scientists have long thought our olfactory abilities rather sluggish. “Intuitively, each sniff feels like taking a long-exposure shot of the chemical environment,” said Dr Wen Zhou, co-author of the research from the Chinese Academy of Sciences, adding that when a smell is detected it can seem like one scent, rather than a discernible mixture of odours that arrived at different times. “Sniffs are also separated in time, occurring seconds apart from one another,” she said. But now researchers have revealed our sense of smell operates much faster than previously thought, suggesting we are as sensitive to rapid changes in odours as we are to rapid changes in colour. A key challenge to probing our sense of smell, said Zhou, is that it has been difficult to create a setup that enables different smelly substances to be presented in a precise sequence in time within a single sniff. However, writing in the journal Nature Human Behaviour, Zhou and colleagues report how they did just that by creating an apparatus in which two bottles containing different scents were hooked up to a nosepiece using tubes of different lengths. These tubes were fitted with miniature check valves that were opened by the act of taking a sniff. © 2024 Guardian News & Media Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29518 - Posted: 10.16.2024

By Angie Voyles Askham Unlike the primary sensory brain areas that process sights and sounds, the one that decodes scents also responds to other stimuli, such as images and words associated with an odor, according to a study published today in Nature. The extent to which neurons in the primary olfactory cortex, which includes the piriform cortex, respond to non-odor stimuli was surprising, says Marc Spehr, head of the Chemosensation Laboratory at RWTH Aachen University, who co-led the study. One neuron, for example, which activated in response to the scent of black licorice, also responded to the word “licorice,” images of the candy and the odor of anise seed, which is unrelated but has a similar scent. Cells in the amygdala also showed multimodal responses; one neuron, for example, responded to a banana scent as well as the word “banana.” “These aren’t odor signals that these cells are encoding; these cells are encoding concepts,” says Kevin Franks, associate professor of neurobiology at Duke University, who was not involved in the work but wrote a News and Views article on it. “So in this part of the brain, traditionally being considered this primary sensory area, you have sensory invariant conceptual representations of specific types of objects. And that’s really, really cool.” Smell-detecting neurons in the nose project into the brain’s olfactory bulb, which then passes information directly to the piriform cortex and other parts of the primary olfactory cortex. That means the piriform cortex lies only two synapses away from the stimuli it decodes, Franks says. In the visual system, on the other hand, a cell two synapses away from a photon is still in the retina, he says. Despite the limited odor processing that happens before the signal reaches the piriform cortex, there have been earlier hints that the area acts more like an association cortex than like other primary sensory areas, says Thorsten Kahnt, investigator at the U.S. National Institute on Drug Abuse, who was not involved in the work. © 2024 Simons Foundation

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29514 - Posted: 10.12.2024

By Shaena Montanari Sea robins skitter across the sea floor with six tiny fins-turned-legs. And at least one species of these bottom feeders is exceptionally skilled at digging up food—so good that other fishes follow these sea robins to snatch up leftover snacks. The sea robins owe this talent to their legs, according to a pair of studies published today in Current Biology. The new work shows that the appendages evolved a specialized sensory system to feel and taste hidden prey. The legs of one common species, for example, are innervated by touch-sensitive neurons and dotted with tiny papillae that express taste receptors. “It’s just really neat to see the molecular components that nature is using to spin out not only new structures, but also new behaviors,” says David Kingsley, professor of developmental biology at Stanford University and an investigator on both studies. The results formalize work from the 1960s and ’70s that first indicated the special chemosensory abilities of sea robins, says Tom Finger, professor of cell and developmental biology at the University of Colorado Anschutz Medical Campus, who was not involved in the new studies. This is “a major, important contribution to show that taste receptors have become expressed in the specialized sensory organ.” This finding “demonstrates, I think, an evolutionary principle, which is that evolution uses the tool kit that’s in place and then just slightly changes it,” says Nicholas Bellono, professor of molecular and cellular biology at Harvard University, who is an investigator on both new studies and also researches unique senses in cephalopods. Last year, he and his colleagues described a similar adaptation in octopuses: “They took this receptor that was for neurotransmission and then just repurposed it with a slight tinkering to now be a sensory receptor. So it’s sort of a theme we keep seeing repeat across the diversity of life.” © 2024 Simons Foundation

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29500 - Posted: 10.02.2024

By Daniela Hirschfeld Peter Mombaerts is a man of strong preferences. He likes Belgian beer — partly, but not entirely, for patriotic reasons. He likes classical music and observing the Earth from above while flying small planes with his amateur pilot’s license. He loves the feel of alpaca clothing during winter. But Mombaerts, who leads the Max Planck Research Unit for Neurogenetics in Frankfurt, Germany, says he has no favorite odor — even though he has been studying smells for more than 30 years. Mombaerts’s research has focused on how the brain processes odors, and on the impressive group of genes encoding odorant receptors in mammals. Humans have about 400 of these genes, which means that 2 percent of our roughly 20,000 genes help us to smell — the largest gene family known to date, as Mombaerts noted back in 2001 in the Annual Review of Genomics and Human Genetics. More than two decades later, it remains the record holder, and Mombaerts continues to delve into the genetics and neuroscience of how we smell the world around us. He spoke with Knowable Magazine about what’s been learned about the genes, receptors and neurons involved in sensing odors — and the mysteries that remain. This interview has been edited for length and clarity. Why did you start working on smell? When studying medicine in my native Belgium in the 1980s, I learned that I don’t really like to work so much with patients. But research interested me. I wanted to do neurobiology. I did my PhD in immunology with mice and genetics, and then moved to neuroscience. It was what I always wanted to do, but I had to find the right topic, the right lab and the right mentor — and all that came together when Linda Buck and Richard Axel published their paper about their discovery of the genes for odorant receptors. This paper came out in the journal Cell on April 5, 1991, and when I read the first few sentences I thought, “That’s what I want to work on.” Axel became my postdoc mentor. When Buck and Axel won the Nobel Prize in Physiology or Medicine in 2004, I wrote a Perspective piece for the New England Journal of Medicine  that I titled “Love at First Smell.” © 2024 Annual Reviews

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29469 - Posted: 09.07.2024

By Kerri Smith The smell in the laboratory was new. It was, in the language of the business, tenacious: for more than a week, the odour clung to the paper on which it had been blotted. To researcher Alex Wiltschko, it was the smell of summertime in Texas: watermelon, but more precisely, the boundary where the red flesh transitions into white rind. “It was a molecule that nobody had ever seen before,” says Wiltschko, who runs a company called Osmo, based in Cambridge, Massachusetts. His team created the compound, called 533, as part of its mission to understand and digitize smell. His goal — to develop a system that can detect, predict or create odours — is a tall order, as molecule 533 shows. “If you looked at the structure, you would never have guessed that it smelled this way.” That’s one of the problems with understanding smell: the chemical structure of a molecule tells you almost nothing about its odour. Two chemicals with very similar structures can smell wildly different; and two wildly different chemical structures can produce an almost identical odour. And most smells — coffee, Camembert, ripe tomatoes — are mixtures of many tens or hundreds of aroma molecules, intensifying the challenge of understanding how chemistry gives rise to olfactory experience. Another problem is working out how smells relate to each other. With vision, the spectrum is a simple colour palette: red, green, blue and all their swirling intermediates. Sounds have a frequency and a volume, but for smell there are no obvious parameters. Where does an odour identifiable as ‘frost’ sit in relation to ‘sauna’? It’s a real challenge to make predictions about smell, says Joel Mainland, a neuroscientist at the Monell Chemical Senses Center, an independent research institute in Philadelphia, Pennsylvania. © 2024 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29463 - Posted: 09.04.2024

By Meghan Rosen Float like a butterfly, sniff out cancer like a bee? Honeybees can detect the subtle scents of lung cancer in the lab — and even the faint aroma of disease that can waft from a patient’s breath. Inspired by the insects’ exquisite olfactory abilities, scientists hooked the brains of living bees up to electrodes, passed different scents under the insects’ antennae and then recorded their brain signals. “It’s very clear — like day and night — whether [a bee] is responding to a chemical or not,” says Debajit Saha, a neural engineer at Michigan State University in East Lansing. Different odors sparked recognizable brain activity patterns, a kind of neural fingerprint for scent, Saha and colleagues report June 4 in Biosensors and Bioelectronics. One day, he says, doctors might be able to use honeybees in cancer clinics as living sensors for early disease detection. Electronic noses, or e-noses, and other types of mechanical odor-sensing equipment exist, but they’re not exactly the bee’s knees. When it comes to scent, Saha says, “biology has this ability to differentiate between very, very similar mixtures, which no other engineered sensors can do.” Scent is an important part of how many insect species communicate, says chemical ecologist Flora Gouzerh of the French National Research Institute for Sustainable Development in Montpellier. For them, “it’s a language,” she says. The idea that animal senses can get a whiff of disease is nothing new; doctors reported a case of a border collie and a Doberman sniffing out their owner’s melanoma in 1989. More recently, scientists have shown that dogs can detect COVID-19 cases by smelling people’s sweat (SN: 6/1/22). A lot of insects probably have disease-detecting abilities, too, Gouzerh says. Ants, for instance, can be trained to pick out the smell of cancer cells grown in a lab dish. But until now, bees’ abilities haven’t been quite so clear, she says. © Society for Science & the Public 2000–2024.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29372 - Posted: 06.26.2024

By Joanne Silberner Think for a minute about the little bumps on your tongue. You probably saw a diagram of those taste bud arrangements once in a biology textbook — sweet sensors at the tip, salty on either side, sour behind them, bitter in the back. But the idea that specific tastes are confined to certain areas of the tongue is a myth that “persists in the collective consciousness despite decades of research debunking it,” according to a review published this month in The New England Journal of Medicine. Also wrong: the notion that taste is limited to the mouth. The old diagram, which has been used in many textbooks over the years, originated in a study published by David Hanig, a German scientist, in 1901. But the scientist was not suggesting that various tastes are segregated on the tongue. He was actually measuring the sensitivity of different areas, said Paul Breslin, a researcher at Monell Chemical Senses Center in Philadelphia. “What he found was that you could detect things at a lower concentration in one part relative to another,” Dr. Breslin said. The tip of the tongue, for example, is dense with sweet sensors but contains the others as well. The map’s mistakes are easy to confirm. If you place a lemon wedge at the tip of your tongue, it will taste sour, and if you put a bit of honey toward the side, it will be sweet. The perception of taste is a remarkably complex process, starting from that first encounter with the tongue. Taste cells have a variety of sensors that signal the brain when they encounter nutrients or toxins. For some tastes, tiny pores in cell membranes let taste chemicals in. Such taste receptors aren’t limited to the tongue; they are also found in the gastrointestinal tract, liver, pancreas, fat cells, brain, muscle cells, thyroid and lungs. We don’t generally think of these organs as tasting anything, but they use the receptors to pick up the presence of various molecules and metabolize them, said Diego Bohórquez, a self-described gut-brain neuroscientist at Duke University. For example, when the gut notices sugar in food, it tells the brain to alert other organs to get ready for digestion. © 2024 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: 29336 - Posted: 06.02.2024

Rudi Zygadlo To celebrate our anniversary, my partner and I dine in a trendy London restaurant in Hackney with a Michelin star – my first time in such a place. A crispy little bonbon is introduced to us simply as “Pine, kvass lees and vin brûlé.” I watch my partner light up, the flickering candle in her eyes, as the waiter sets the thing down. The impact of the aroma has already registered on her face. With her first bite she is transported to her childhood in Massachusetts. “Gosh,” she gasps, closing her eyes as a New England virgin pine forest explodes in her mind. When she blinks open, returning to the here and now, she looks at me guiltily. I take a bite and wince. No coniferous wonderland for me. Just unpleasant bitterness, confined very much to the tongue. I am pleased for her, truly. I’m a magnanimous guy. But from that moment on, the whole evening is a bit of a spectator sport and, by the end of it, I have a feeling that she is even playing her enjoyment down, muting her reactions, as if to say, “You’re not missing out.” She finds some dishes prove more successful than others – the sweetness of cherry, an umami-rich mushroom – but I am missing out: on the nuances, the emotions, the memories. The smell. It’s been three years since I lost it. November 2020. I was living with three friends in a flat in Glasgow when we all caught Covid in the pre-vaccine days. Two of us lost our smell and never fully recovered it. We’re in good company. Around 700,000 people in the UK are believed to have total smell loss caused by the virus, with around six million still experiencing some olfactory dysfunction. I estimate mine has returned by about 30%, but it’s inconsistent and often distorted. To summarise my symptoms of anosmia, as total or partial loss of smell is known: some things have a faint odour, some don’t smell as they should and others don’t smell at all. For example: basil smells mild but good, ground coffee and a certain brand of toothpaste smell like fish and, mercifully, shit doesn’t stink at all. Apart from the latter, all bad news.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29070 - Posted: 12.31.2023

Jon Hamilton If this year's turkey seems over brined, blame your brain. The question of when salty becomes too salty is decided by a special set of neurons in the front of the brain, researchers report in the journal Cell. A separate set of neurons in the back of the brain adjusts your appetite for salt, the researchers showed in a series of experiments on mice. "Sodium craving and sodium tolerance are controlled by completely different types of neurons," says Yuki Oka, an author of the study and a professor of biology at Caltech. The finding could have health implications because salt ingestion is a "major issue" in many countries, including the United States, says Nirupa Chaudhari, a professor of physiology and biology at the University of Miami's Miller School of Medicine. Too much salt can cause high blood pressure and raise the risk for heart disease and stroke, says Chaudhari, who was not involved in the study. Craving, to a point The study sought to explain the complicated relationship that people and animals have with salt, also known as sodium chloride. We are happy to drink sodas, sports drinks, and even tap water that contain a little salt, Oka says. "But if you imagine a very high concentration of sodium like ocean water, you really hate it." This aversion to super salty foods and beverages holds unless your body is really low on salt, something that's pretty rare in people these days. But experiments with mice found that when salt levels plummet, the tolerance for salty water goes up. "Animals start liking ocean water," Oka says. The reason for this change involves at least two different interactions between the body and brain, Oka's team found. When the concentration of sodium in the bloodstream begins to fall below healthy levels, a set of neurons in the back of the brain respond by dialing up an animal's craving for salt. "If you stimulate these neurons, then animals run to a sodium source and start eating," Oka says. Meanwhile, a different set of neurons in the front of the brain monitors the saltiness of any food or water the mice are consuming. And usually, these neurons will set an upper limit on saltiness. © 2023 npr

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: 29024 - Posted: 11.26.2023

By Hannah Docter-Loeb Paxlovid can prevent severe illness from COVID-19, but it comes with a price: In many users, the antiviral drug leaves a weird, metallic aftertaste that can last for days—a condition nicknamed “Paxlovid mouth.” Now, researchers say they’ve figured out why. A component of Paxlovid activates one of the tongue’s bitter taste receptors even at low levels, which may draw out the yuck factor, the team reports this month in Biochemical and Biophysical Research Communications. The work could lead to ways to alleviate the unpleasant side effect. The study is a “good first step” in teasing apart the mechanism behind Paxlovid mouth, says Alissa Nolden, a sensory scientist at the University of Massachusetts Amherst who was not involved with the research. But she says more work will be needed to truly understand why the metallic taste lingers for so long. Paxlovid is composed of two antivirals: nirmatrelvir and ritonavir. Nirmatrelvir blocks a key protein that SARS-CoV-2 needs to replicate. Ritonavir helps maintain the level of nirmatrelvir in the blood. Scientists have suspected that ritonavir is the primary culprit behind Paxlovid mouth. It was originally used in HIV medications and was known to directly taste bitter. A recent study also demonstrated that the compound acts on several tongue receptors that respond to bitter taste. However, ritonavir’s bitterness is short-lived, says Peihua Jiang, a molecular biologist at the Monell Chemical Senses Center, an independent research institute. So in the new study, he and colleagues looked more closely at nirmatrelvir. They added the antiviral to various groups of cells, each collection with a different member of the 25 human bitter taste receptors. They then identified the receptors that responded most vigorously to the compound by changes in a fluorescence marker in the cells. Nirmatrelvir seemed to hone in on TAS2R1, one of the primary receptors responsible for the bitter aftertaste of antiviral medicines, the researchers found. The compound activated the receptor even when its concentration was relatively low, which could explain why Paxlovid causes a persistent bitter taste.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29016 - Posted: 11.22.2023

By Sean Cummings If a bite of dandelion greens or extra-dark chocolate makes you pucker, there’s good reason. Bitterness can indicate the presence of toxins in potential foods, and animals long ago honed the ability to ferret out harsh tastes. But the ability to sense bitterness may be even older than many presumed, a new study finds. It likely first evolved in vertebrates roughly 460 million years ago, when sharks and other cartilaginous fishes separated from bony vertebrates like ourselves, researchers report today in the Proceedings of the National Academy of Sciences. The bitter taste receptor identified in a pair of shark species may mirror a sort of all-purpose bitterness detector that our common ancestor possessed. “Given how quickly taste receptors change, to have this one receptor conserved over 460 million years, that’s pretty astounding,” says Craig Montell, a neurobiologist at the University of California, Santa Barbara who was not involved in the study. “The ability to react to the particular bitter chemicals that activate it must be really important.” Humans and other bony vertebrates experience bitterness thanks to taste 2 receptors, or T2Rs, which are proteins that transmit taste information to the brain. But scientists had never found T2Rs in cartilaginous vertebrates such as sharks and rays. That led many to assume these receptors had evolved after their lineage split from the bony vertebrates. Yet sharks and other cartilaginous fish do have smell receptors closely related to bitter taste receptors. That made Sigrun Korsching, a neurobiologist at the University of Cologne, wonder: Could bitter taste perception be even older than most believed? To find out, she and colleagues examined 17 genomes from various species of sharks, skates, and sawfish. Twelve of these had genes that coded for taste receptors similar to T2Rs, which they dubbed T2R1s. In the lab, the researchers implanted genes for these receptors from two of the species—bamboo sharks and catsharks—into human kidney cells, then exposed them to 94 bitter substances. These included resveratrol, found in foods such as grapes, peanuts, and cranberries, and amarogentin, a compound from the gentian plant considered one of the most astringent tastes in the world.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 29006 - Posted: 11.15.2023

Saima Sidik When the scent of morning coffee wafts past the nose, the brain encodes which nostril it enters, new research shows1. Integrating information from both nostrils might help us to identify the odour. The results were published today in Current Biology. A region of the brain called the piriform cortex, which spans the brain’s two hemispheres, is known to receive and process information about scents. However, scientists were unsure whether the two sides of the piriform cortex react to smells in unison or independently. To investigate this question, researchers recruited people with epilepsy who were undergoing brain surgery to identify the areas of their brains responsible for their seizures. Participants were awake for the surgery, during which the scientists delivered scents to one or both nostrils through tiny tubes that reached roughly one centimetre into each nostril. The authors took advantage of electrodes placed in the study participants’ brains to take readings of activity in the piriform cortex. In reality, scents rarely hit only one nostril. Instead, they’re likely to enter one nostril slightly ahead of the other. “The question to ask is, well, can the brain exploit these potential differences?” says Naz Dikecligil, a neuroscientist at the University of Pennsylvania in Philadelphia and a co-author of the study. The findings suggest that the brain does make use of the different arrival times. When an odour was delivered to a single nostril, the side of the brain closest to that nostril reacted first, and a reaction then followed in the opposite side of the brain. “There seem to be actually two odour representations, corresponding to odour information coming from each nostril,” Dikecligil says. When the researchers provided a scent to both nostrils simultaneously, they saw that both sides of the brain recognized the scent faster than either did when it was delivered through only one nostril. This suggests that the two sides do synergize to some degree, even though one lags behind the other in encoding a scent, Dikecligil says. © 2023 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28992 - Posted: 11.08.2023

By Tim Vernimmen For humans, division of labor has become a necessity: No person in the world has all the knowledge and skills to perform all the tasks that are required to keep our highly technological societies afloat. This has made us entirely dependent on each other, leaving us individually vulnerable. We really can’t make it on our own. From archaeological findings, we can reconstruct more or less how this situation evolved. Initially, everyone was doing more or less the same thing. But because food was shared among people living in hunter-gatherer groups, some were able to specialize in tasks other than finding food, such as fashioning tools, treating illnesses or cultivating plants. These skills enriched the group but made the specialists even more dependent on others. This further reinforced cooperation among group members and pushed our species to even higher levels of specialization — and prosperity. “Societies that have highly developed task-sharing and division of labor between group members are conspicuous because of their exceptional ecological success,” says Michael Taborsky, a behavioral biologist at the University of Bern in Switzerland. And he doesn’t just mean us: Extensive division of labor also can be seen among many social insects — ants, wasps, bees and termites — in which individuals in large colonies often specialize in particular tasks, making them impressively effective. “It is no exaggeration,” Taborsky says, “to say that societies” — of both humans and social insects — “predominate life on Earth.” But how did this division of labor evolve? Why does it seem to be rare outside of our species and the social insects? Is it, in fact, as rare as it seems? Taborsky, who has studied cooperation in animals for decades, has become increasingly interested in these questions. In March 2023, he and Barbara Taborsky, his wife and colleague, organized a scientific workshop on the topic in Berlin to which they invited a number of other experts. Over the course of two days, the group discussed how division of labor may have evolved over time, and what mechanisms allow it to develop, over and over again, in every colony of certain species. One of the invited scientists was Jennifer Fewell, a social insect biologist at Arizona State University who coauthored an influential overview of division of labor in the Annual Review of Entomology in 2001 and has studied the subject for decades. In social insect colonies, she says, “there is no central controller telling everybody what to do, but instead, the division of labor emerges from the interaction between individuals.” © 2023 Annual Reviews

Related chapters from BN: Chapter 6: Evolution of the Brain and Behavior; Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28944 - Posted: 10.05.2023

By Hannah Docter-Loeb Growing up, Julian Meeks knew what a life without a sense of smell could look like. He’d watched this grandfather navigate the condition, known as anosmia, observing that he didn’t perceive flavor and only enjoyed eating very salty or meaty foods. The experience influenced him, in part, to study chemosensation, which involves both smell and taste. Meeks, now a professor of neuroscience at the University of Rochester, told Undark that neither gets much attention compared to other senses: “Often, they’re thought of as second or third in order of importance.” The pandemic changed that, at least somewhat, after it left millions of people without a sense of smell, albeit some temporarily. In particular, more researchers started looking at a specific type of condition called acquired anosmia. Common causes include traumatic brain injury, or TBI, neurodegenerative diseases like Parkinson’s or Alzheimer’s, or following a viral infection like Covid-19. Due to the pandemic, “many people found it scientifically interesting to focus their research on smell,” said Valentina Parma, the assistant director of the Monell Chemical Senses Center, a nonprofit research institute in Philadelphia. By one account, NIH funding of anosmia research nearly doubled between 2019 and 2021. But many of the research findings do not apply to those who have lacked the ability to smell since birth: congenital anosmics. And, despite the increased attention to smell loss more broadly, some researchers still face challenges in funding studies. In March 2023, for instance, Meeks received a peer review for a small grant, of less than $275,000, from the National Institutes of Health, with which he had planned to look into anosmia in the context of TBI. For Meeks, the response was frustrating. One expert reviewer in particular “didn’t really understand why there would be any need to establish a preclinical model of anosmia with TBI,” he said, noting that the reviewer also wrote that because anosmia is not a major health problem, the value of the research was low. The comment, Meeks added, was “quite discouraging.”

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28931 - Posted: 09.27.2023

By Amber Dance We’ve all heard of the five tastes our tongues can detect — sweet, sour, bitter, savory-umami and salty. But the real number is actually six, because we have two separate salt-taste systems. One of them detects the attractive, relatively low levels of salt that make potato chips taste delicious. The other one registers high levels of salt — enough to make overly salted food offensive and deter overconsumption. Exactly how our taste buds sense the two kinds of saltiness is a mystery that’s taken some 40 years of scientific inquiry to unravel, and researchers haven’t solved all the details yet. In fact, the more they look at salt sensation, the weirder it gets. Many other details of taste have been worked out over the past 25 years. For sweet, bitter and umami, it’s known that molecular receptors on certain taste bud cells recognize the food molecules and, when activated, kick off a series of events that ultimately sends signals to the brain. Sour is slightly different: It is detected by taste bud cells that respond to acidity, researchers recently learned. In the case of salt, scientists understand many details about the low-salt receptor, but a complete description of the high-salt receptor has lagged, as has an understanding of which taste bud cells host each detector. “There are a lot of gaps still in our knowledge — especially salt taste. I would call it one of the biggest gaps,” says Maik Behrens, a taste researcher at the Leibniz Institute for Food Systems Biology in Freising, Germany. “There are always missing pieces in the puzzle.” A fine balance Our dual perception of saltiness helps us to walk a tightrope between the two faces of sodium, an element that’s crucial for the function of muscles and nerves but dangerous in high quantities. To tightly control salt levels, the body manages the amount of sodium it lets out in urine, and controls how much comes in through the mouth. © 2023 Annual Reviews

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28908 - Posted: 09.16.2023

By David Grimm Apart from Garfield’s legendary love of lasagna, perhaps no food is more associated with cats than tuna. The dish is a staple of everything from The New Yorker cartoons to Meow Mix jingles—and more than 6% of all wild-caught fish goes into cat food. Yet tuna (or any seafood for that matter) is an odd favorite for an animal that evolved in the desert. Now, researchers say they have found a biological explanation for this curious craving. In a study published this month in Chemical Senses, scientists report that cat taste buds contain the receptors needed to detect umami—the savory, deep flavor of various meats, and one of the five basic tastes in addition to sweet, sour, salty, and bitter. Indeed, umami appears to be the primary flavor cats seek out. That’s no surprise for an obligate carnivore. But the team also found these cat receptors are uniquely tuned to molecules found at high concentrations in tuna, revealing why our feline friends seem to prefer this delicacy over all others. “This is an important study that will help us better understand the preferences of our familiar pets,” says Yasuka Toda, a molecular biologist at Meiji University and a leader in studying the evolution of umami taste in mammals and birds. The work could help pet food companies develop healthier diets and more palatable medications for cats, says Toda, who was not involved with the industry-funded study. Cats have a unique palate. They can’t taste sugar because they lack a key protein for sensing it. That’s probably because there’s no sugar in meat, says Scott McGrane, a flavor scientist and research manager for the sensory science team at the Waltham Petcare Science Institute, which is owned by pet food–maker Mars Petcare UK. There’s a saying in evolution, he says: “If you don’t use it, you lose it.” Cats also have fewer bitter taste receptors than humans do—a common trait in uber-carnivores. But cats must taste something, McGrane reasoned, and that something is likely the savory flavor of meat. In humans and many other animals, two genes—Tas1r1 and Tas1r3—encode proteins that join together in taste buds to form a receptor that detects umami. Previous work had shown that cats express the Tas1r3 gene in their taste buds, but it was unclear whether they had the other critical puzzle piece.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28885 - Posted: 08.26.2023