Chapter 8. General Principles of Sensory Processing, Touch, and Pain

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Chloe Tenn On October 4, physiologist David Julius and neurobiologist Arden Patapoutian were awarded the Nobel Prize in Physiology or Medicine for their work on temperature, pain, and touch perception. Julius researched the burning sensation people experience from chilies, and identified an ion channel, TRPV1 that is activated by heat. Julius and Patapoutian then separately reported on the TRPM8 ion channel that senses menthol’s cold in 2002. Patapoutian’s group went on to discover the PIEZO1 and PIEZO2 ion channels that are involved in sensing mechanical pressure. The Nobel Committee wrote that the pair’s work inspired further research into understanding how the nervous system senses temperature and mechanical stimuli and that the laureates “identified critical missing links in our understanding of the complex interplay between our senses and the environment.” This year saw innovations in augmenting the brain’s capabilities by plugging it in to advanced computing technology. For example, a biology teacher who lost her vision 16 years ago was able to distinguish shapes and letters with the help of special glasses that interfaced with electrodes implanted in her brain. Along a similar vein, a computer connected to a brain-implant system discerned brain signals for handwriting in a paralyzed man, enabling him to type up to 90 characters per minute with an accuracy above 90 percent. Such studies are a step forward for technologies that marry cutting-edge neuroscience and computational innovation in an attempt to improve people’s lives. © 1986–2021 The Scientist.

Keyword: Pain & Touch; Language
Link ID: 28134 - Posted: 12.31.2021

By Cara Giaimo Sign up for Science Times Get stories that capture the wonders of nature, the cosmos and the human body. Get it sent to your inbox. It’s tough out there for a mouse. Outdoors, its enemies lurk on all sides: owls above, snakes below, weasels around the bend. Indoors, a mouse may find itself targeted by broom-wielding humans or bored cats. Mice compensate with sharp senses of sight, hearing and smell. But they may have another set of tools we’ve overlooked. A paper published last week in Royal Society Open Science details striking similarities between the internal structures of certain small mammal and marsupial hairs and those of man-made optical instruments. In this paper as well as other unpublished experiments, the author, Ian Baker, a physicist who works in private industry, posits that these hairs may act as heat-sensing “infrared antennae” — further cluing the animals into the presence of warm-blooded predators. Although much more work is necessary to connect the structure of these hairs to this potential function, the study paints an “intriguing picture,” said Tim Caro, a professor of evolutionary ecology at the University of Bristol in England who was not involved. Dr. Baker has spent decades working with thermal imaging cameras, which visualize infrared radiation produced by heat. For his employer, the British defense company Leonardo UK Ltd., he researches and designs infrared sensors. But in his spare time he often takes the cameras to fields and forests near his home in Southampton, England, to film wildlife. Over the years, he has developed an appreciation for “how comfortable animals are in complete darkness,” he said. That led him to wonder about the extent of their sensory powers. © 2021 The New York Times Company

Keyword: Pain & Touch; Evolution
Link ID: 28120 - Posted: 12.18.2021

Jon Hamilton Scientists may have learned why opioids depress breathing while relieving pain. The finding could lead to pain drugs that don't cause respiratory failure, the usual cause of death in opioid overdoses. When people feel pain, they tend to breathe faster. When they take an opioid to kill that pain, their breathing slows down. Now scientists think they know how pain and respiration are connected in the brain. NPR's Jon Hamilton reports that the discovery could eventually lead to safer pain drugs. JON HAMILTON, BYLINE: Sung Han has been studying the link between pain and breathing in his lab at the Salk Institute in San Diego. But he got a real-world demonstration recently while taking a shower. SUNG HAN: I forgot to change the temperature, and the cold water just suddenly came out and covered my entire body. And then I just - I was breathing really fast. HAMILTON: A typical reaction to what Han calls aversive sensory information - and he thinks he knows the cause. Han's lab has identified a brain circuit in mice that appears to link the emotional experience of pain to breathing rhythm. Han says the circuit involves two populations of brain cells both found in the same small area of the brain stem. HAN: One population regulate pain and the other population regulate breathing, and that's the reason why pain and breathing are interacting each other. HAMILTON: They're linked together. If that's also true in people, it would help explain the mysterious connection between breathing and emotion, which has puzzled scientists for centuries. And the finding, which appears in the journal Neuron, could also have practical applications. That's because both groups of brain cells - the ones for breathing and the ones for pain - respond to opioids. Han says this is why an overdose can be fatal. © 2021 npr

Keyword: Pain & Touch; Drug Abuse
Link ID: 28117 - Posted: 12.18.2021

By Lisa Sanders, M.D. The 66-year-old man had just started his third lap at the community swimming pool outside Poughkeepsie, N.Y., when it struck. As he was turning his head to take a breath, an octopus of pain wrapped around the right side of his skull, starting at the joint where the jaw connects and slamming across his face and head with tentacles of squeezing agony. For a moment he was paralyzed — first with pain, then with fear. He couldn’t breathe; he could barely move. He struggled to the side of the pool and hung on, his breath ragged through involuntarily clenched teeth. His wife hurried over. He was a good swimmer; what was wrong? She saw his lips move and leaned closer. His jaw was clenched. “I can’t speak,” he mumbled. She helped him out of the pool. “We’re going to go to urgent care,” she said as she handed him a towel. These strange pains had been tormenting the man for nearly three weeks. It started as a headache that woke him from a dead sleep, a squeezing pressure deep inside his brain. He got up and took some acetaminophen. When he awoke the next morning, the headache was gone, but the regions around his head and face where the pressure had been strongest felt strangely tender. He couldn’t even brush his hair on the right side of his head. Bizarre as this was, he most likely would have soon forgotten about it except that it happened again the next night — and just about every night since. The pain in his jaw started a couple of days later. Opening and closing his mouth, and especially chewing, made his jaw throb. Eating anything more solid than mashed potatoes triggered excruciating pain. He went to his dentist, who poked and prodded. The only tenderness was in the joint where the jaw attached to the skull. It’s most likely TMJ, the dentist concluded — temporomandibular joint pain. That joint and the many attached muscles make speech and facial expressions possible. Lots of people have pain there, the dentist added. Bad habits like jaw-clenching and tooth-grinding aggravate the joint. The treatment is behavior modification to unlearn these habits, and sometimes a bite block, a custom-made piece of acrylic worn at night to protect teeth from injury. © 2021 The New York Times Company

Keyword: Pain & Touch; Neuroimmunology
Link ID: 28113 - Posted: 12.15.2021

By David Dobbs Chronic pain is both one of the world’s most costly medical problems, affecting one in every five people, and one of the most mysterious. In the past two decades, however, discoveries about the crucial role played by glia — a set of nervous system cells once thought to be mere supports for neurons — have rewritten chronic pain science. These findings have given patients and doctors a hard-science explanation that chronic pain previously lacked. By doing so, this emerging science of chronic pain is beginning to influence care — not by creating new treatments, but by legitimizing chronic pain so that doctors take it more seriously. Although glia are scattered throughout the nervous system and take up almost half its space, they long received far less scientific attention than neurons, which do the majority of signaling in the brain and body. Some types of glia resemble neurons, with roughly starfish-like bodies, while others look like structures built with Erector sets, their long, straight structural parts joined at nodes. When first discovered in the mid-1800s, glia — from the Greek word for glue — were thought to be just connective tissue holding neurons together. Later they were rebranded as the nervous system’s janitorial staff, as they were found to feed neurons, clean up their waste and take out their dead. In the 1990s they were likened to secretarial staff when it was discovered they also help neurons communicate. Research over the past 20 years, however, has shown that glia don’t just support and respond to neuronal activity like pain signals — they often direct it, with enormous consequences for chronic pain. If you’re hearing this for the first time and you’re one of the billion-plus people on Earth who suffer from chronic pain (meaning pain lasting beyond three to six months that has no apparent cause or has become independent of the injury or illness that caused it), you might be tempted to say that your glia are botching their pain-management job. © 2021 The New York Times Company

Keyword: Pain & Touch; Glia
Link ID: 28075 - Posted: 11.13.2021

By James Gallagher An innovative type of medicine - called gene silencing - is set to be used on the NHS for people who live in crippling pain. The drug treats acute intermittent porphyria, which runs in families and can leave people unable to work or have a normal life. Clinical trials have shown severe symptoms were cut by 74% with the drug. While porphyria is rare, experts say the field of gene silencing has the potential to revolutionise medicine. Sisters Liz Gill and Sue Burrell have both had their lives turned around by gene silencing. Before treatment, Liz, from County Durham, remembers the trauma of living in "total pain" and, at its worst, she spent two years paralysed in hospital. Younger sister Sue says she "lost it all overnight" when she was suddenly in and out of hospital, made redundant and did know whether her partner would stick with her (he did). "It was scary," she tells me. Both became used to taking potent opioid painkillers on a daily basis. But even morphine could not block the pain during a severe attack that needed hospital treatment. Gene silencing gets to the root-cause of the sisters' disease rather than just managing their symptoms. Their porphyria leads to a build-up of toxic proteins in the body, that cause the physical pain. Gene silencing "mutes" a set of genetic instructions to block that protein production. Both had been taking the therapy as part of a clinical trial and are still getting monthly injections. © 2021 BBC.

Keyword: Pain & Touch
Link ID: 28046 - Posted: 10.23.2021

Brenda Patoine Science likes to package its successes in neat stories that show a clear progression from this to that. The “bench-to-bedside” story—when biological insights yield targeted treatments—is a long-time favorite. Reality, however, doesn’t always cooperate, and history is littered with basic-science discoveries that seemed important but failed to yield viable treatments. When they do succeed, it’s cause for celebration—and awards. Migraine research is an example. Although it is the second most disabling condition in the world, affecting one billion people, migraine had long been relegated to the backwaters of scientific research. Only recently has research bloomed—scientific papers sharply increased from the 1990s onward, with discoveries in basic science driving a new class of drugs that some in the field are calling game changers. This year, the recognition of four migraine researchers with a major neuroscience award has pushed the field into the limelight of science. The 2021 Brain Prize recognizes science that embodies the so-called bench-to-bedside research described above. That’s a jargony term scientists seem to love that denotes the rare and wonderful occurrence when laboratory research aimed at illuminating fundamental mechanisms (the “bench”) yields insights that lead to drugs that ultimately help millions of sick people (the “bedside”). In the case of migraine research, the leading character is a neuropeptide called calcitonin gene-related peptide (CGRP). © 2021 The Dana Foundation.

Keyword: Pain & Touch
Link ID: 28040 - Posted: 10.16.2021

Jordana Cepelewicz We often appreciate the world around us in terms of its glorious sights, stirring sounds and evocative smells, all of which mark important stimuli and changes in our environment. But senses that are no less crucial to our survival are often taken for granted, including our abilities to register heat, cold and touch, a form of perception called somatosensation. Because of them, we can feel the warmth of the sun or the gentle caress of a breeze against our skin, as well as the positions and movement of our own bodies. In fact, the somatosensory neurons that make all these sensations possible constitute the largest sensory system in mammals. Scientists knew that for somatosensation to occur, there must be molecular receptors on some cells that could detect temperature and touch, and could convert those stimuli into electrical and chemical signals for the nervous system to process. For the discovery of some of those receptors David Julius, a physiologist at the University of California, San Francisco, and Ardem Patapoutian, a molecular biologist and neuroscientist at Scripps Research in La Jolla, have now been awarded the 2021 Nobel Prize in Physiology or Medicine. Julius and his colleagues started with questions about receptors for heat and pain. To find answers, they turned to capsaicin, the compound that causes us to experience a burning and sometimes painful sensation when we eat chili peppers or other spicy food. Based on our physiological response to the chemical, which includes sweating, capsaicin seemed to be inducing the nervous system to register a change in body temperature. To figure out how, Julius and his team screened millions of DNA fragments for a gene that could induce a response to the compound in cells that typically don’t react to it at all. After an arduous search, and what the Nobel Prize committee called “a high-risk project,” the researchers identified a gene that allowed cells to sense capsaicin. It encoded a novel ion channel protein, later called TRPV1, that Julius and his team discovered could be activated by hot temperatures perceived as painful. All Rights Reserved © 2021

Keyword: Pain & Touch
Link ID: 28025 - Posted: 10.06.2021

Amanda Heidt Qin Liu studies sneezing for a personal reason: her entire family suffers from seasonal allergies. “Until you experience something chronically, it is really hard to appreciate how disruptive it can be,” says Liu, a neuroscientist at Washington University in St. Louis. And given the role of sneezing in pathogen transmission, a better understanding of the molecular underpinnings of the phenomenon could one day help scientists mitigate or treat infectious diseases. When Liu first started looking into the mechanisms governing sneezing, she found that scientists know surprisingly little about how this process works. While prior research had identified a region in the brains of cats and humans that is active during sneezing, the exact pathways involved in turning a stimulus like pollen or spicy food into a sneeze remained unknown. To study sneezing in more detail, Liu and her team developed a new model by exposing mice to irritants such as histamine and capsaicin—a chemical in spicy peppers—and characterizing the physical properties of their resulting sneezes. Then, focusing on that previously discovered sneeze center, located in the brain’s ventromedial spinal trigeminal nucleus (SpV), Liu attempted to map the neural pathway. SNEEZE TRIGGER: When exposed to allergens such as histamine or chemical irritants such as capsaicin (1), sensory neurons in the noses of mice produce a peptide called neuromedin B (NMB). This signaling molecule binds to neurons in a region of the brainstem known as the ventromedial spinal trigeminal nucleus (SpV), which is known to be active during sneezing (2). These neurons send electrical signals (3) to neurons in another brainstem region called the caudal ventral respiratory group (cVRG), which controls exhalation, thus driving the initiation and propagation of sneezing (4). Ablating the nasal neurons or disrupting NMB signaling led to a significantly reduced sneezing reflex in the mice. WEB | PDF © 1986–2021 The Scientist.

Keyword: Brain imaging; Pain & Touch
Link ID: 28014 - Posted: 10.02.2021

By Baland Jalal Obsessive-compulsive disorder (OCD) has puzzled artists and scientists for centuries. Afflicting one in 50 people, OCD can take several forms, such as compulsively putting things in just the right order or checking if the stove is turned off 10 times in a row. One type of OCD that affects nearly half of those with the condition entails irresistible washing urges. People with this type can spend hours scrubbing their hands in agitation after touching something as trivial as a doorknob even though they know this makes no sense. There is currently a shortage of effective therapies for OCD: 40 percent of patients do not benefit from existing treatments. A major issue is that today’s treatments are often too stressful. First-line “nonpharmacological therapies” involve telling patients to repeatedly touch things such as toilet seats and then refrain from washing their hands. But recent work by my colleagues and me has found something surprising: people diagnosed with OCD appear to have a more malleable “sense of self,” or brain-based “self-representation” or “body image”—the feeling of being anchored here and now in one’s body—than those without the disorder. This finding suggests new ways to treat OCD and perhaps unexpected insights into how our brain creates a distinction between “self” and “other.” In our recent experiments, for example, we showed that people with and without OCD responded differently to a well-known illusion. In our first study, a person without OCD watched as an experimenter used a paintbrush to stroke a rubber hand and the subject’s hidden real hand in precise synchrony. This induces the so-called rubber hand illusion: the feeling that a fake hand is your hand. When the experimenter stroked the rubber hand and the real one out of sync, the effect was not induced (or was greatly diminished). This compelling illusion illustrates how your brain creates your body image based on statistical correlations. It’s extremely unlikely for such stroking to be seen on a rubber hand and simultaneously felt on a hidden real one by chance. So your brain concludes, however illogically, that the rubber hand is part of your body. © 2021 Scientific American

Keyword: OCD - Obsessive Compulsive Disorder; Pain & Touch
Link ID: 27980 - Posted: 09.08.2021

Allison Whitten Our mushy brains seem a far cry from the solid silicon chips in computer processors, but scientists have a long history of comparing the two. As Alan Turing put it in 1952: “We are not interested in the fact that the brain has the consistency of cold porridge.” In other words, the medium doesn’t matter, only the computational ability. Today, the most powerful artificial intelligence systems employ a type of machine learning called deep learning. Their algorithms learn by processing massive amounts of data through hidden layers of interconnected nodes, referred to as deep neural networks. As their name suggests, deep neural networks were inspired by the real neural networks in the brain, with the nodes modeled after real neurons — or, at least, after what neuroscientists knew about neurons back in the 1950s, when an influential neuron model called the perceptron was born. Since then, our understanding of the computational complexity of single neurons has dramatically expanded, so biological neurons are known to be more complex than artificial ones. But by how much? To find out, David Beniaguev, Idan Segev and Michael London, all at the Hebrew University of Jerusalem, trained an artificial deep neural network to mimic the computations of a simulated biological neuron. They showed that a deep neural network requires between five and eight layers of interconnected “neurons” to represent the complexity of one single biological neuron. All Rights Reserved © 2021

Keyword: Brain imaging; Vision
Link ID: 27978 - Posted: 09.04.2021

Nicola Davis Premature babies appear to feel less pain during medical procedures when they are spoken to by their mothers, researchers have found. Babies that are born very early often have to spend time in neonatal intensive care units, and may need several painful clinical procedures. The situation can also mean lengthy separation from parents. Now researchers say they have found the sound of a mother’s voice seems to decrease the pain experienced by their baby during medical procedures. Dr Manuela Filippa, of the University of Geneva and first author of the study, said the research might not only help parents, by highlighting that they can play an important role while their baby is in intensive care, but also benefit the infants. Advertisement Last man out: the haunting image of America’s final moments in Afghanistan “We are trying to find non-pharmacological ways to lower the pain in these babies,” she said, adding that there was a growing body of evidence that parental contact with preterm babies could be important for a number of reasons, including attachment. Filippa said the team focused on voice because it was not always possible for parents to hold their babies in intensive care, while voice could be a powerful tool to share emotion. Mothers’ voices were studied in particular because infants would already have heard it in the womb. But Filippa said that did not mean a father’s voice could not become as familiar over time. “We are [also] running studies on fathers’ vocal contacts,” she said. Writing in the journal Scientific Reports, Filippa and colleagues at the University of Geneva, Parini hospital in Italy and the University of Valle d’Aosta, report how they examined the pain responses of 20 premature babies in neonatal intensive care to a routine procedure in which the foot is pricked and a few drops of blood collected. © 2021 Guardian News & Media Limited

Keyword: Pain & Touch; Development of the Brain
Link ID: 27973 - Posted: 09.01.2021

By Christiane Gelitz, Maddie Bender | To a chef, the sounds of lip smacking, slurping and swallowing are the highest form of flattery. But to someone with a certain type of misophonia, these same sounds can be torturous. Brain scans are now helping scientists start to understand why. People with misophonia experience strong discomfort, annoyance or disgust when they hear particular triggers. These can include chewing, swallowing, slurping, throat clearing, coughing and even audible breathing. Researchers previously thought this reaction might be caused by the brain overactively processing certain sounds. Now, however, a new study published in the Journal of Neuroscience has linked some forms of misophonia to heightened “mirroring” behavior in the brain: those affected feel distress while their brains act as if they are mimicking the triggering mouth movements. “This is the first breakthrough in misophonia research in 25 years,” says psychologist Jennifer J. Brout, who directs the International Misophonia Research Network and was not involved in the new study. The research team, led by Newcastle University neuroscientist Sukhbinder Kumar, analyzed brain activity in people with and without misophonia when they were at rest and while they listened to sounds. These included misophonia triggers (such as chewing), generally unpleasant sounds (like a crying baby), and neutral sounds. The brain's auditory cortex, which processes sound, reacted similarly in subjects with and without misophonia. But in both the resting state and listening trials, people with misophonia showed stronger connections between the auditory cortex and brain regions that control movements of the face, mouth and throat. Kumar found this connection became most active in participants with misophonia when they heard triggers specific to the condition. © 2021 Scientific American,

Keyword: Hearing; Attention
Link ID: 27955 - Posted: 08.21.2021

By Sabrina Imbler In a way, nausea is our trusty personal bodyguard. Feeling nauseated is widely accepted to be an evolutionary defense measure that protects people from pathogens and parasites. The urge to gag or vomit is “well-suited” to defend ourselves against things we swallow that might contain pathogens, according to Tom Kupfer, a psychological scientist at Nottingham Trent University in England. But vomiting is somewhat futile against a tick, an ectoparasite that latches on to skin, not stomachs. In an experiment that produced both stomach churning and skin crawling sensations — I can confirm these and some other physiological responses firsthand — Dr. Kupfer and Daniel Fessler, an evolutionary anthropologist from the University of California, Los Angeles, argue in a paper published on Wednesday in the journal Proceedings of the Royal Society B that humans have evolved to defend themselves against ectoparasites through a skin response that elicits scratching. Although some outside experts say more research is needed, the findings align with some understandings of the evolution of disgust. “It makes sense to have developed adaptive defensive strategies against the ‘nasty’ ones,” Cécile Sarabian, a cognitive ecologist studying animal disgust at the Kyoto University Primate Research Institute in Japan, wrote in an email. The disgusting investigation began in 2017 on the grounds of Chicheley Hall in Buckinghamshire, England. Here, Dr. Kupfer was presenting findings to colleagues on trypophobia, the aversion to clustered holes experienced by some people. His data showed that participants with trypophobia often reacted to holey images with the urge to itch or scratch, sometimes to the point of bleeding. Dr. Kupfer suggested that trypophobia might not represent fear, but rather a disgust reaction to signs of parasites or infectious diseases, which can both result in clusters of lesions or pustules.

Keyword: Pain & Touch
Link ID: 27926 - Posted: 07.28.2021

By Tom Zeller Jr. I have headaches. Not the low-grade, annoying, “I’ve got a headache” sort of headaches. I get those, too. Most everyone does, and they are a drag. No, when I say that I get headaches, I mean that at intervals that are largely unpredictable, a knot of pain rises deep inside my head, invariably sensed behind my right eyeball. It then swiftly clicks up through the intensity scale, racing past that dull ache you might get from staring at the screen too long, leapfrogging over that doozy you had the morning after your brother’s wedding, skipping past the agonizing-but-fleeting stab of an ice-cream headache, and arriving, within a matter of minutes, at a pain so piercing and sustained that I can only grip something sturdy, rock back and forth, and grunt until it subsides. Mine are what doctors call one of the “primary headaches” — recurring and often excruciating disorders that are not byproducts of another condition (or self-inflicted by last night’s cocktails), but relentless, and in many ways still poorly understood disorders unto themselves. We know them by common names like migraine, which affects tens of millions of Americans, disproportionately women. I suffer from another flavor known as cluster headaches (technically “trigeminal autonomic cephalalgias”). And there are others, with myriad and imperfectly drawn lines distinguishing them. If you experience migraines or cluster headaches — and research suggests that more than a billion people worldwide do — you probably know something about shuttling from doctor to doctor looking for someone who “gets it.” You know what it’s like to gladly gobble up pills that don’t really work and that leave you miserable in other ways. And you might even know the same sort of incredulous exasperation that has driven me to wonder, from my fetal position on the bathroom floor: “How is it possible that science can’t fix a damn headache?” © 2021 The New York Times Company

Keyword: Pain & Touch
Link ID: 27924 - Posted: 07.24.2021

Elena Renken For decades, neuroscientists have treated the brain somewhat like a Geiger counter: The rate at which neurons fire is taken as a measure of activity, just as a Geiger counter’s click rate indicates the strength of radiation. But new research suggests the brain may be more like a musical instrument. When you play the piano, how often you hit the keys matters, but the precise timing of the notes is also essential to the melody. “It’s really important not just how many [neuron activations] occur, but when exactly they occur,” said Joshua Jacobs, a neuroscientist and biomedical engineer at Columbia University who reported new evidence for this claim last month in Cell. For the first time, Jacobs and two coauthors spied neurons in the human brain encoding spatial information through the timing, rather than rate, of their firing. This temporal firing phenomenon is well documented in certain brain areas of rats, but the new study and others suggest it might be far more widespread in mammalian brains. “The more we look for it, the more we see it,” Jacobs said. Abstractions navigates promising ideas in science and mathematics. Journey with us and join the conversation. Some researchers think the discovery might help solve a major mystery: how brains can learn so quickly. The phenomenon is called phase precession. It’s a relationship between the continuous rhythm of a brain wave — the overall ebb and flow of electrical signaling in an area of the brain — and the specific moments that neurons in that brain area activate. A theta brain wave, for instance, rises and falls in a consistent pattern over time, but neurons fire inconsistently, at different points on the wave’s trajectory. In this way, brain waves act like a clock, said one of the study’s coauthors, Salman Qasim, also of Columbia. They let neurons time their firings precisely so that they’ll land in range of other neurons’ firing — thereby forging connections between neurons. All Rights Reserved © 2021

Keyword: Brain imaging
Link ID: 27898 - Posted: 07.08.2021

By Anil Ananthaswamy “Everything became imbued with a sense of vitality and life and vividness. If I picked up a pebble from the beach, it would move. It would glisten and gleam and sparkle and be absolutely captivating,” says neuroscientist Anil Seth. “Somebody looking at me would see me staring at a stone for hours.” Or what seemed like hours to Seth. A researcher at the UK’s University of Sussex, he studies how the brain helps us perceive the world within and without, and is intrigued by what psychedelics such as LSD can tell us about how the brain creates these perceptions. So a few years ago, he decided to try some, in controlled doses and with trusted people by his side. He had a notebook to keep track of his experiences. “I didn’t write very much in the notebook,” he says, laughing. Instead, while on LSD, he reveled in a sense of well-being and marveled at the “fluidity of time and space.” He found himself staring at clouds and seeing them change into faces of people he was thinking of. If his attention drifted, the clouds morphed into animals. Seth went on to try ayahuasca, a hallucinogenic brew made from a shrub and a vine native to South America and often used in shamanistic rituals there. This time, he had a more emotional trip that dredged up powerful memories. Both experiences strengthened Seth’s conviction that psychedelics have great potential for teaching us about the inner workings of the brain that give rise to our perceptions. He’s not alone. Armed with fMRI scans, EEG recordings, computational models of the brain and reports from volunteers tripping on psychedelics, a small but growing number of neuroscientists are trying to take advantage of these drugs and the hallucinations they induce to better understand how the brain produces perceptions. © 2021 Annual Reviews, Inc

Keyword: Drug Abuse; Vision
Link ID: 27883 - Posted: 06.29.2021

By Emily Conover Scientists could be a step closer to understanding how some birds might exploit quantum physics to navigate. Researchers suspect that some songbirds use a “quantum compass” that senses the Earth’s magnetic field, helping them tell north from south during their annual migrations (SN: 4/3/18). New measurements support the idea that a protein in birds’ eyes called cryptochrome 4, or CRY4, could serve as a magnetic sensor. That protein’s magnetic sensitivity is thought to rely on quantum mechanics, the math that describes physical processes on the scale of atoms and electrons (SN: 6/27/16). If the idea is shown to be correct, it would be a step forward for biophysicists who want to understand how and when quantum principles can become important in various biological processes. In laboratory experiments, the type of CRY4 in retinas of European robins (Erithacus rubecula) responded to magnetic fields, researchers report in the June 24 Nature. That’s a crucial property for it to serve as a compass. “This is the first paper that actually shows that birds’ cryptochrome 4 is magnetically sensitive,” says sensory biologist Rachel Muheim of Lund University in Sweden, who was not involved with the research. Scientists think that the magnetic sensing abilities of CRY4 are initiated when blue light hits the protein. That light sets off a series of reactions that shuttle around an electron, resulting in two unpaired electrons in different parts of the protein. Those lone electrons behave like tiny magnets, thanks to a quantum property of the electrons called spin. © Society for Science & the Public 2000–2021.

Keyword: Animal Migration; Vision
Link ID: 27882 - Posted: 06.29.2021

Ed Yong Carl Schoonover and Andrew Fink are confused. As neuroscientists, they know that the brain must be flexible but not too flexible. It must rewire itself in the face of new experiences, but must also consistently represent the features of the external world. How? The relatively simple explanation found in neuroscience textbooks is that specific groups of neurons reliably fire when their owner smells a rose, sees a sunset, or hears a bell. These representations—these patterns of neural firing—presumably stay the same from one moment to the next. But as Schoonover, Fink, and others have found, they sometimes don’t. They change—and to a confusing and unexpected extent. Schoonover, Fink, and their colleagues from Columbia University allowed mice to sniff the same odors over several days and weeks, and recorded the activity of neurons in the rodents’ piriform cortex—a brain region involved in identifying smells. At a given moment, each odor caused a distinctive group of neurons in this region to fire. But as time went on, the makeup of these groups slowly changed. Some neurons stopped responding to the smells; others started. After a month, each group was almost completely different. Put it this way: The neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time. This is, of course, just one study, of one brain region, in mice. But other scientists have shown that the same phenomenon, called representational drift, occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery. Schoonover and Fink told me that they don’t know why it happens, what it means, how the brain copes, or how much of the brain behaves in this way. How can animals possibly make any lasting sense of the world if their neural responses to that world are constantly in flux? (c) 2021 by The Atlantic Monthly Group

Keyword: Chemical Senses (Smell & Taste)
Link ID: 27852 - Posted: 06.11.2021

By Nikk Ogasa Most Uber drivers need a smartphone to get to their destinations. But sharks, it seems, need nothing more than their own bodies—and Earth’s magnetic field. A new study suggests some sharks can read Earth’s field like a map and use it to navigate the open seas. The result adds sharks to the long list of animals—including birds, sea turtles, and lobsters—that navigate with a mysterious magnetic sense. “It’s great that they’ve finally done this magnetic field study on sharks,” says Michael Winklhofer, a biophysicist at the Carl von Ossietzky University of Oldenburg in Germany, who was not involved in the study. In 2005, scientists reported that a great white shark swam from South Africa to Australia and back again in nearly a straight line—a feat that led some scientists to propose the animals relied on a magnetic sense to steer themselves. And since at least the 1970s, researchers have suspected that the elasmobranchs—a group of fish containing sharks, rays, skates, and sawfish—can detect magnetic fields. But no one had shown that sharks use the fields to locate themselves or navigate, partly because the animals aren’t so easy to work with, Winklhofer says. “It’s one thing if you have a small lobster, or a baby sea turtle, but when you work with sharks, you have to upscale everything.” Bryan Keller, an ecologist at Florida State University, and his colleagues decided to do just that. The researchers lined a bedroom-size cage with copper wire and placed a small swimming pool in the center of the cage. By running an electrical current through the wiring, they could generate a custom magnetic field in the center of the pool. The team then collected 20 juvenile bonnethead sharks—a species known to migrate hundreds of kilometers—from a shoal off the Florida coast. They placed the sharks into the pool, one at a time, and let them swim freely under three different magnetic fields, applied in random succession. One field mimicked Earth’s natural field at the spot where the sharks were collected, whereas the others mimicked the fields at locations 600 kilometers north and 600 kilometers south of their homes. © 2021 American Association for the Advancement of Science.

Keyword: Animal Migration
Link ID: 27814 - Posted: 05.12.2021