Chapter 2. Neurophysiology: The Generation, Transmission, and Integration of Neural Signals

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By Phie Jacobs Is there really such a thing as a “male” or “female” brain? Sex certainly seems to affect a person’s risk of developing various psychiatric and other brain-related conditions—but scientists aren’t entirely sure why. Attention-deficit/hyperactivity disorder for example, is more commonly diagnosed in individuals who were assigned male at birth (AMAB), whereas those assigned female at birth (AFAB) are more likely to exhibit symptoms of anxiety. It’s unclear, however, whether these differences are actually driven by sex, or have more to do with how people are perceived and treated based on their sex or gender. Now, new research suggests sex and gender are associated with distinct brain networks. Published today in Science Advances, the findings draw on brain imaging data from nearly 5000 children to reveal that gender and sex aren’t just distinct from one another in society—they also play unique roles in biology. In science, the term “biological sex” encompasses a variety of genetic, hormonal, and anatomical characteristics. People are typically assigned “male” or “female” as their sex at birth, although the medical establishment in recent years has begun to acknowledge that sex doesn’t always fall neatly into binary categories. Indeed, about 0.05% of children born in the United States are assigned intersex at birth. Gender, by contrast, has more to do with a person’s attitudes, feelings, and behavior—and may not always align with the sex they were assigned at birth. These nuances often go unrecognized in neuroscience, says Sheila Shanmugan, a reproductive psychiatrist at the University of Pennsylvania who wasn’t involved in the new study. Sex and gender-based differences in the brain “have historically been understudied,” she explains, “and terms describing each are often conflated.” © 2024 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Brain imaging
Link ID: 29393 - Posted: 07.13.2024

By Erin Garcia de Jesús In spring 2022, a handful of red foxes in Wisconsin were behaving oddly. Veterinary pathologist Betsy Elsmo learned that a local wildlife rehabilitation center was caring for foxes with neurological symptoms like seizures, tremors, uncoordinated movements and lethargy. But tests for common pathogens like canine distemper virus and rabies that typically cause the symptoms came back negative. Then a red fox kit tested positive for influenza A. This group of viruses includes seasonal flus that cause respiratory disease in people and many other strains that commonly circulate among animals such as waterfowl and other birds. “I was surprised,” says Elsmo, of the University of Wisconsin–Madison. “And to be honest, at first I kind of wrote it off.” That is, until a veterinary technician at the rehab center sent Elsmo a study describing cases of avian influenza in red foxes in the Netherlands. Examinations of the Wisconsin kit’s tissues under the microscope revealed lesions in the brain, lung and heart that matched what had been seen in the Netherlands animals. “And I thought, I think it is [bird flu],” she recalls. Additional testing confirmed the diagnosis in the kit and the other foxes, Elsmo and colleagues reported in the December 2023 Emerging Infectious Diseases. The animals had contracted a lethal strain of H5N1 avian influenza that emerged in late 2020 in Europe and has since spread around the world. At the time infections were discovered in the Wisconsin red foxes, bird flu was expanding its incursion into North America. Since H5N1 arrived on North American shores in December 2021, it has infected animals as wide-ranging as polar bears, skunks, sea lions, bottlenosed dolphins and cows (SN: 7/8/24). And one unwelcome revelation of the ongoing outbreak is the virus’s propensity to invade the brains of myriad mammals. © Society for Science & the Public 2000–2024.

Keyword: Stress
Link ID: 29392 - Posted: 07.13.2024

By Tyler Sloan If I ask you to picture a group of “neurons firing,” what comes to mind? For most people, it’s a few isolated neurons flashing in synchrony. This type of minimalist representation of neurons is common within neuroscience, inspired in part by Santiago Ramón y Cajal’s elegant depictions of the nervous system. His work left a deep mark on our intuitions, but the method he used—Golgi staining—highlights just 1 to 5 percent of neurons. More than a century later, researchers have mapped out brain connectivity in such detail that it easily becomes overwhelming; I vividly recall an undergraduate neurophysiology lecture in which the professor showed a wiring diagram of the primary visual cortex to make the point that it was too complex to understand. We’ve reached a point where simple wiring diagrams no longer suffice to represent what we’re learning about the brain. Advances in experimental and computational neuroscience techniques have made it possible to map brains in more detail than ever before. The wiring diagram for the whole fly brain, for example, mapped at single-synapse resolution, comprises 2.7 million cell-to-cell connections and roughly 150 million synapses. Building an intuitive understanding of this type of complexity will require new tools for representing neural connectivity in a way that is both meaningful and compact. To do this, we will have to embrace the elaborate and move beyond the single neuron to a more “maximalist” approach to visualizing the nervous system. I spent my Ph.D. studying the spinal cord, where commissural growth cones are depicted as pioneers on a railhead extending through uncharted territory. The watershed moment for me was seeing a scanning electron micrograph of the developing spinal cord for the first time and suddenly understanding the growth cone’s dense environment—its path was more like squeezing through a crowded concert than wandering across an empty field. I realized how poor my own intuitions were, which nudged me toward learning the art of 3D visualization. © 2024 Simons Foundation

Keyword: Brain imaging; Development of the Brain
Link ID: 29385 - Posted: 07.09.2024

By Sara Reardon By eavesdropping on the brains of living people, scientists have created the highest-resolution map yet of the neurons that encode the meanings of various words1. The results hint that, across individuals, the brain uses the same standard categories to classify words — helping us to turn sound into sense. The study is based on words only in English. But it’s a step along the way to working out how the brain stores words in its language library, says neurosurgeon Ziv Williams at the Massachusetts Institute of Technology in Cambridge. By mapping the overlapping sets of brain cells that respond to various words, he says, “we can try to start building a thesaurus of meaning”. The brain area called the auditory cortex processes the sound of a word as it enters the ear. But it is the brain’s prefrontal cortex, a region where higher-order brain activity takes place, that works out a word’s ‘semantic meaning’ — its essence or gist. Previous research2 has studied this process by analysing images of blood flow in the brain, which is a proxy for brain activity. This method allowed researchers to map word meaning to small regions of the brain. But Williams and his colleagues found a unique opportunity to look at how individual neurons encode language in real time. His group recruited ten people about to undergo surgery for epilepsy, each of whom had had electrodes implanted in their brains to determine the source of their seizures. The electrodes allowed the researchers to record activity from around 300 neurons in each person’s prefrontal cortex. © 2024 Springer Nature Limited

Keyword: Language; Brain imaging
Link ID: 29383 - Posted: 07.06.2024

By Paula Span About a month ago, Judith Hansen popped awake in the predawn hours, thinking about her father’s brain. Her father, Morrie Markoff, was an unusual man. At 110, he was thought to be the oldest in the United States. His brain was unusual, too, even after he recovered from a stroke at 99. Although he left school after the eighth grade to work, Mr. Markoff became a successful businessman. Later in life, his curiosity and creativity led him to the arts, including photography and sculpture fashioned from scrap metal. He was a healthy centenarian when he exhibited his work at a gallery in Los Angeles, where he lived. At 103, he published a memoir called “Keep Breathing.” He blogged regularly, pored over The Los Angeles Times daily, discussed articles in Scientific American and followed the national news on CNN and “60 Minutes.” Now he was nearing death, enrolled in home hospice care. “In the middle of the night, I thought, ‘Dad’s brain is so great,’” said Ms. Hansen, 82, a retired librarian in Seattle. “I went online and looked up ‘brain donation.’” Her search led to a National Institutes of Health web page explaining that its NeuroBioBank, established in 2013, collected post-mortem human brain tissue to advance neurological research. Through the site, Ms. Hansen contacted the nonprofit Brain Donor Project. It promotes and simplifies donations through a network of university brain banks, which distribute preserved tissue to research teams. Tish Hevel, the founder of the project, responded quickly, putting Ms. Hansen and her brother in touch with the brain bank at the University of California, Los Angeles. Brain donors may have neurological and other diseases, or they may possess healthy brains, like Mr. Markoff’s. “We’re going to learn so much from him,” Ms. Hevel said. “What is it about these superagers that allows them to function at such a high level for so long?” © 2024 The New York Times Company

Keyword: Development of the Brain; Brain imaging
Link ID: 29379 - Posted: 07.06.2024

By Adolfo Plasencia Recently, a group of Australian researchers demonstrated a “mind-reading” system called BrainGPT. The system can, according to its creators, convert thoughts (recorded with a non-invasive electrode helmet) into words that are displayed on a screen. Essentially, BrainGPT connects a multitasking EEG encoder to a large language model capable of decoding coherent and readable sentences from EEG signals. Is the mind, the last frontier of privacy, still a safe place to think one’s thoughts? I spoke with Harvard-based behavioral neurologist Alvaro Pascual-Leone, a leader in the study of neuroplasticity and noninvasive brain stimulation, about what it means and how we can protect ourselves. The reality is that the ability to read the brain and influence activity is already here. It’s no longer only in the realm of science fiction. Now, the question is, what exactly can we access and manipulate in the brain? Consider this example: If I instruct you to move a hand, I can tell if you are preparing to move, say, your right hand. I can even administer a precise “nudge” to your brain and make you move your right hand faster. And you would then claim, and fully believe, that you moved it yourself. However, I know that, in fact, it was me who moved it for you. I can even force you to move your left hand—which you were not going to move—and lead you to rationalize why you changed your mind when in fact, our intervention led to that action you perceive as your choice. We have done this experiment in our laboratory. In humans, we can modify brain activity by reading and writing in the brain, so to speak, though we can affect only very simple things right now. In animals, we can do much more complex things because we have much more precise control of the neurons and their timing. But the capacity for that modulation of smaller circuits progressively down to individual neurons in humans is going to come, including much more selective modification with optogenetic alternatives—that is, using light to control the activity of neurons. © 2024 NautilusNext Inc.,

Keyword: Brain imaging
Link ID: 29377 - Posted: 07.03.2024

Jon Hamilton About 170 billion cells are in the brain, and as they go about their regular tasks, they produce waste — a lot of it. To stay healthy, the brain needs to wash away all that debris. But how exactly it does this has remained a mystery. Now, two teams of scientists have published three papers that offer a detailed description of the brain's waste-removal system. Their insights could help researchers better understand, treat and perhaps prevent a broad range of brain disorders. The papers, all published in the journal Nature, suggest that during sleep, slow electrical waves push the fluid around cells from deep in the brain to its surface. There, a sophisticated interface allows the waste products in that fluid to be absorbed into the bloodstream, which takes them to the liver and kidneys to be removed from the body. One of the waste products carried away is amyloid, the substance that forms sticky plaques in the brains of patients with Alzheimer's disease. This illustration demonstrates how the thin film of sensors could be applied to the brain during surgery. There's growing evidence that in Alzheimer's disease, the brain's waste-removal system is impaired, says Jeffrey Iliff, who studies neurodegenerative diseases at the University of Washington but was not a part of the new studies. The new findings should help researchers understand precisely where the problem is and perhaps fix it, Iliff says. "If we restore drainage, can we prevent the development of Alzheimer's disease?" he asks. The new studies come more than a decade after Iliff and Dr. Maiken Nedergaard, a Danish scientist, first proposed that the clear fluids in and around the brain are part of a system to wash away waste products. The scientists named it the glymphatic system, a nod to the body's lymphatic system, which helps fight infection, maintain fluid levels and filter out waste products and abnormal cells. © 2024 npr

Keyword: Sleep
Link ID: 29369 - Posted: 06.26.2024

By Miryam Naddaf Researchers have developed a four-dimensional model of spinal-cord injury in mice, which shows how nearly half a million cells in the spinal cord respond over time to injuries of varying severity. The model, known as a cell atlas, could help researchers to resolve outstanding questions and develop new treatments for people with spinal-cord injury (SCI). “If you know what every single cell on the spinal cord is doing in response to injury, you could use that knowledge to develop tailor-made and mechanism-based therapies,” says Mark Anderson, a neurobiologist at the Swiss Federal Institute of Technology in Geneva, Switzerland, who worked on the atlas. “Things don’t need to be a shot in the dark.” Anderson and his colleagues used machine-learning algorithms to build the atlas by mapping data from RNA sequencing and other cell-biology techniques. They described the work in a Nature paper published today1 and have made the entire atlas available through an online platform. The atlas is a valuable resource for testing hypotheses about SCI, says Binhai Zheng, who studies spinal-cord regeneration at the University of California, San Diego. “There are a lot of hidden treasures.” The researchers examined sections of the spinal cord, sampled from 52 injured and uninjured mice at 1, 4, 7, 14, 30 and 60 days after injury. Their analysis involved 18 experimental SCI conditions, including different types of injury and levels of severity. They used RNA-sequencing tools to explore how 482,825 cells responded to injury over time. © 2024 Springer Nature Limited

Keyword: Brain imaging; Brain Injury/Concussion
Link ID: 29368 - Posted: 06.26.2024

Hannah Devlin Science correspondent A UK teenager with severe epilepsy has become the first person in the world to be fitted with a brain implant aimed at bringing seizures under control. Oran Knowlson’s neurostimulator sits under the skull and sends electrical signals deep into the brain, reducing his daytime seizures by 80%. His mother, Justine, said that her son had been happier, chattier and had a much better quality of life since receiving the device. “The future looks hopeful, which I wouldn’t have dreamed of saying six months ago,” she said. Martin Tisdall, a consultant paediatric neurosurgeon who led the surgical team at Great Ormond Street hospital (Gosh) in London, said: “For Oran and his family, epilepsy completely changed their lives and so to see him riding a horse and getting his independence back is absolutely astounding. We couldn’t be happier to be part of their journey.” Oran, who is 13 and lives in Somerset, had the surgery in October as part of a trial at Gosh in partnership with University College London, King’s College hospital and the University of Oxford. Oran has Lennox-Gastaut syndrome, external, a treatment-resistant form of epilepsy which he developed at the age of three. Between then and having the device fitted, he hasn’t had a single day without a seizure and sometimes suffered hundreds in a day. He often lost consciousness and would stop breathing, needing resuscitation. This means Oran needed round-the-clock care, as seizures could happen at any time of day, and he was at a significantly increased risk of sudden unexpected death in epilepsy (Sudep). © 2024 Guardian News & Media Limited

Keyword: Epilepsy; Robotics
Link ID: 29367 - Posted: 06.24.2024

Jon Hamilton A flexible film bristling with tiny sensors could make surgery safer for patients with a brain tumor or severe epilepsy. The experimental film, which looks like Saran wrap, rests on the brain’s surface and detects the electrical activity of nerve cells below. It’s designed to help surgeons remove diseased tissue while preserving important functions like language and memory. “This will enable us to do a better job,” says Dr. Ahmed Raslan, a neurosurgeon at Oregon Health and Science University who helped develop the film. The technology is similar in concept to sensor grids already used in brain surgery. But the resolution is 100 times higher, says Shadi Dayeh, an engineer at the University of California, San Diego, who is leading the development effort. In addition to aiding surgery, the film should offer researchers a much clearer view of the neural activity responsible for functions including movement, speech, sensation, and even thought. “We have these complex circuits in our brains,” says John Ngai, who directs the BRAIN Initiative at the National Institutes of Health, which has funded much of the film’s development. “This will give us a better understanding of how they work.” Mapping an ailing brain The film is intended to improve a process called functional brain mapping, which is often used when a person needs surgery to remove a brain tumor or tissue causing severe epileptic seizures. © 2024 npr

Keyword: Brain imaging; Epilepsy
Link ID: 29357 - Posted: 06.13.2024

Hannah Devlin Science correspondent A 10-minute brain scan could detect dementia several years before people develop noticeable symptoms, a study suggests. Scientists used a scan of “resting” brain activity to identify whether people would go on to develop dementia, with an estimated 80% accuracy up to nine years before people received a diagnosis. If the findings were confirmed in a larger cohort, the scan could become a routine procedure in memory clinics, scientists said. “We’ve known for a long time that the function of the brain starts to change many years before you get dementia symptoms,” said Prof Charles Marshall, who led the work at Queen Mary University of London. “This could help us to be more precise at identifying those changes using an MRI scan that you could do on any NHS scanner.” The research comes as a new generation of Alzheimer’s drugs are on the horizon. The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) is assessing lecanemab, made by Eisai and Biogen, and donanemab, made by Eli Lilly, and both drugs are widely expected to be licensed this year. “Predicting who is going to get dementia in the future will be vital for developing treatments that can prevent the irreversible loss of brain cells that causes the symptoms of dementia,” Marshall said. The researchers used functional MRI (fMRI) scans from 1,100 UK Biobank volunteers to detect changes in the brain’s “default mode network” (DMN). The scan measures correlations in brain activity between different regions while the volunteer lies still, not doing any particular task. The network, which reflects how effectively different regions are communicating with each other, is known to be particularly vulnerable to Alzheimer’s disease. © 2024 Guardian News & Media Limited

Keyword: Alzheimers; Brain imaging
Link ID: 29349 - Posted: 06.08.2024

By Gemma Conroy Researchers have developed biodegradable, wireless sensors that can monitor changes in the brain following a head injury or cancer treatment, without invasive surgery. In rats and pigs, the soft sensors performed just as well as conventional wired sensors for up to a month after being injected under the skull. The gel-based sensors measure key health markers, including temperature, pH and pressure. “It is quite likely this technology will be useful for people in medical settings,” says study co-author Yueying Yang, a biomedical engineer at Huazhong University of Science and Technology (HUST) in Wuhan, China. The findings were published today in Nature1. “It’s a very comprehensive study,” says Christopher Reiche, who develops implantable microdevices at the University of Utah in Salt Lake City. For years, scientists have been developing brain sensors that can be implanted inside the skull. But many of these devices rely on wires to transmit data to clinicians. The wires are difficult to insert and remove, and create openings in the skin for viruses and bacteria to enter the body. Wireless sensors offer a solution to this problem, but are thwarted by their limited communication range and relatively large size. Developing sensors that can access and monitor the brain is “extremely difficult”, says Omid Kavehei, a biomedical engineer who specializes in neurotechnology at the University of Sydney in Australia. To overcome these challenges, Yang and her colleagues created a set of 2-millimetre cube-shaped sensors out of hydrogel, a soft, flexible material that’s often used in tissue regeneration and drug delivery. The gel sensors change shape under different temperatures, pressures and pH conditions, and respond to vibrations caused by variations in blood flow in the brain. When the sensors are implanted under the skull and scanned with an ultrasound probe — a tool that is already used to image the human brain in clinics — these changes are detectable in the form of ultrasonic waves that pass through the skull. The tiny gel-cubes completely dissolve in saline solution after around four months, and begin to break down in the brain after five weeks. © 2024 Springer Nature Limited

Keyword: Brain Injury/Concussion; Brain imaging
Link ID: 29346 - Posted: 06.06.2024

By Rebecca Horne The drawings and photographs of Santiago Ramón y Cajal are familiar to any neuroscientist—and probably anyone even remotely interested in the field. Most people who take a cursory look at his iconic images might assume that he created them using only direct observation. But that’s not the case, according to a paper published in March 2024 by Dawn Hunter, visual artist and associate professor of art at the University of South Carolina, and her colleagues. For instance, the Golgi-stained tissue Ramón y Cajal drew contained neurons that were cut in half—so he painstakingly reconstructed the cells by drawing from elements in multiple slides. And he also fleshed out his illustrations using educated guesses and classical drawing principles, such as contrast and occlusion. In this way, Ramón y Cajal’s art training was essential to his research, Hunter says. She came across Ramón y Cajal’s drawings while creating illustrations for a neuroscience textbook. “The first time I saw his work, out of pure inspiration, I decided to draw it,” she says. “It was in those moments of drawing that I realized his process was more profound and conceptually layered than merely retracing pencil lines with ink. Examining Ramón y Cajal’s work through the act of drawing is a more active experience than viewing his work as a gallery visitor or in a textbook.” In 2015, Hunter installed her drawings and paintings alongside original Ramón y Cajal works in an ongoing exhibition at the U.S. National Institutes of Health (NIH). That effort led to a Fulbright fellowship to Spain in 2017, providing her access to the Legado Cajal archives at the Instituto Cajal National Archives, which contain thousands of Ramón y Cajal artifacts. Hunter spoke to The Transmitter about her research in Spain and her realizations about how Ramón y Cajal worked as an artist and as a scientist. The Transmitter: What do you think your work contributes that is new? Dawn Hunter: It spells out the connection to [Ramón y Cajal’s] art training. There are some things that to me as a painter are obvious to zero in on that nobody’s really talked about. For example, Ramón y Cajal’s copying of the Renaissance painter Rafael’s entire portfolio. That in itself is a profound thing. © 2024 Simons Foundation

Keyword: Brain imaging
Link ID: 29338 - Posted: 06.04.2024

By Liqun Luo The brain is complex; in humans it consists of about 100 billion neurons, making on the order of 100 trillion connections. It is often compared with another complex system that has enormous problem-solving power: the digital computer. Both the brain and the computer contain a large number of elementary units—neurons and transistors, respectively—that are wired into complex circuits to process information conveyed by electrical signals. At a global level, the architectures of the brain and the computer resemble each other, consisting of largely separate circuits for input, output, central processing, and memory.1 Which has more problem-solving power—the brain or the computer? Given the rapid advances in computer technology in the past decades, you might think that the computer has the edge. Indeed, computers have been built and programmed to defeat human masters in complex games, such as chess in the 1990s and recently Go, as well as encyclopedic knowledge contests, such as the TV show Jeopardy! As of this writing, however, humans triumph over computers in numerous real-world tasks—ranging from identifying a bicycle or a particular pedestrian on a crowded city street to reaching for a cup of tea and moving it smoothly to one’s lips—let alone conceptualization and creativity. So why is the computer good at certain tasks whereas the brain is better at others? Comparing the computer and the brain has been instructive to both computer engineers and neuroscientists. This comparison started at the dawn of the modern computer era, in a small but profound book entitled The Computer and the Brain, by John von Neumann, a polymath who in the 1940s pioneered the design of a computer architecture that is still the basis of most modern computers today.2 Let’s look at some of these comparisons in numbers (Table 1). © 2024 NautilusNext Inc.,

Keyword: Stroke
Link ID: 29331 - Posted: 05.29.2024

By Elissa Welle A new study suggests that the brain clears less waste during sleep and under anesthesia than while in other states—directly contradicting prior results that suggest sleep initiates that process. The findings are stirring fresh debate on social media and elsewhere over the glymphatic system hypothesis, which contends that convective flow of cerebrospinal fluid clears the sleeping brain of toxins. The new work, published 13 May in Nature Neuroscience, proposes that fluid diffusion is responsible for moving waste throughout the brain. It uses a different method than the earlier studies—injecting tracers into mouse brain tissue instead of cerebrospinal fluid—which is likely a more reliable way to understand how the fluid moves through densely packed neurons, says Jason Rihel, professor of behavioral genetics at University College London, who was not involved in any of the studies on brain clearance. The findings have prompted some sleep researchers, including Rihel, to question the existence of a glymphatic system and whether brain clearance is tied to sleep-wake states, he says. But leading proponents of the sleep-induced clearance theory are pushing back against the study’s techniques. The new study is “misleading” and “extremely poorly done,” says Maiken Nedergaard, professor of neurology at the University of Rochester Medical Center, whose 2013 study on brain clearance led to the hypothesis of a glymphatic system. She says she plans to challenge the work in a proposed Matters Arising commentary for Nature Neuroscience. Inserting needles into the brain damages the tissue, and injecting fluid, as the team behind the new work did, increases intracranial pressure, says Jonathan Kipnis, professor of pathology and immunology at Washington University School of Medicine in St. Louis. Kipnis and his colleagues published a study in February in support of the glymphatic system hypothesis that suggests neural activity facilitates brain clearance. “You disturb the system when you inject into the brain,” Kipnis says, “and that’s why we were always injecting in the CSF.” © 2024 Simons Foundation

Keyword: Sleep
Link ID: 29327 - Posted: 05.25.2024

By Laura Sanders It’s a bit like seeing a world in a grain of sand. Except the view, in this case, is the exquisite detail inside a bit of human brain about half the size of a grain of rice. Held in that minuscule object is a complex collective of cells, blood vessels, intricate patterns and biological puzzles. Scientists had hints of these mysteries in earlier peeks at this bit of brain (SN: 6/29/21). But now, those details have been brought into new focus by mapping the full landscape of some 57,000 cells, 150 million synapses and their accompanying 23 centimeters of blood vessels, researchers report in the May 10 Science. The full results, the scientists hope, may lead to greater insights into how the human brain works. “We’re going in and looking at every individual connection attached to every cell — a very high level of detail,” says Viren Jain, a computational neuroscientist at Google Research in Mountain View, Calif. The big-picture goal of brain mapping efforts, he says, is “to understand how human brains work and what goes wrong in various kinds of brain diseases.” The newly mapped brain sample was removed during a woman’s surgery for epilepsy, so that doctors could reach a deeper part of the brain. The bit, donated with the woman’s consent, was from the temporal lobe of the cortex, the outer part of the brain involved in complex mental feats like thinking, remembering and perceiving. This digital drawing of a person's head shows the brain inside. An arrow points to the bottom left side of the brain. After being fixed in a preservative, the brain bit was sliced into almost impossibly thin wisps, and then each slice was imaged with a high-powered microscope. Once these views were collected, researchers used computers to digitally reconstruct the three-dimensional objects embedded in the piece of brain. © Society for Science & the Public 2000–2024

Keyword: Brain imaging; Development of the Brain
Link ID: 29324 - Posted: 05.25.2024

By Amanda Heidt For the first time, a brain implant has helped a bilingual person who is unable to articulate words to communicate in both of his languages. An artificial-intelligence (AI) system coupled to the brain implant decodes, in real time, what the individual is trying to say in either Spanish or English. The findings1, published on 20 May in Nature Biomedical Engineering, provide insights into how our brains process language, and could one day lead to long-lasting devices capable of restoring multilingual speech to people who can’t communicate verbally. “This new study is an important contribution for the emerging field of speech-restoration neuroprostheses,” says Sergey Stavisky, a neuroscientist at the University of California, Davis, who was not involved in the study. Even though the study included only one participant and more work remains to be done, “there’s every reason to think that this strategy will work with higher accuracy in the future when combined with other recent advances”, Stavisky says. The person at the heart of the study, who goes by the nickname Pancho, had a stroke at age 20 that paralysed much of his body. As a result, he can moan and grunt but cannot speak clearly. In his thirties, Pancho partnered with Edward Chang, a neurosurgeon at the University of California, San Francisco, to investigate the stroke’s lasting effects on his brain. In a groundbreaking study published in 20212, Chang’s team surgically implanted electrodes on Pancho’s cortex to record neural activity, which was translated into words on a screen. Pancho’s first sentence — ‘My family is outside’ — was interpreted in English. But Pancho is a native Spanish speaker who learnt English only after his stroke. It’s Spanish that still evokes in him feelings of familiarity and belonging. “What languages someone speaks are actually very linked to their identity,” Chang says. “And so our long-term goal has never been just about replacing words, but about restoring connection for people.” © 2024 Springer Nature Limited

Keyword: Language; Robotics
Link ID: 29321 - Posted: 05.23.2024

By Carissa Wong Researchers have mapped a tiny piece of the human brain in astonishing detail. The resulting cell atlas, which was described today in Science1 and is available online, reveals new patterns of connections between brain cells called neurons, as well as cells that wrap around themselves to form knots, and pairs of neurons that are almost mirror images of each other. The 3D map covers a volume of about one cubic millimetre, one-millionth of a whole brain, and contains roughly 57,000 cells and 150 million synapses — the connections between neurons. It incorporates a colossal 1.4 petabytes of data. “It’s a little bit humbling,” says Viren Jain, a neuroscientist at Google in Mountain View, California, and a co-author of the paper. “How are we ever going to really come to terms with all this complexity?” The brain fragment was taken from a 45-year-old woman when she underwent surgery to treat her epilepsy. It came from the cortex, a part of the brain involved in learning, problem-solving and processing sensory signals. The sample was immersed in preservatives and stained with heavy metals to make the cells easier to see. Neuroscientist Jeff Lichtman at Harvard University in Cambridge, Massachusetts, and his colleagues then cut the sample into around 5,000 slices — each just 34 nanometres thick — that could be imaged using electron microscopes. Jain’s team then built artificial-intelligence models that were able to stitch the microscope images together to reconstruct the whole sample in 3D. “I remember this moment, going into the map and looking at one individual synapse from this woman’s brain, and then zooming out into these other millions of pixels,” says Jain. “It felt sort of spiritual.” When examining the model in detail, the researchers discovered unconventional neurons, including some that made up to 50 connections with each other. “In general, you would find a couple of connections at most between two neurons,” says Jain. Elsewhere, the model showed neurons with tendrils that formed knots around themselves. “Nobody had seen anything like this before,” Jain adds. © 2024 Springer Nature Limited

Keyword: Brain imaging; Development of the Brain
Link ID: 29304 - Posted: 05.14.2024

By Miryam Naddaf Scientists have developed brain implants that can decode internal speech — identifying words that two people spoke in their minds without moving their lips or making a sound. Although the technology is at an early stage — it was shown to work with only a handful of words, and not phrases or sentences — it could have clinical applications in future. Similar brain–computer interface (BCI) devices, which translate signals in the brain into text, have reached speeds of 62–78 words per minute for some people. But these technologies were trained to interpret speech that is at least partly vocalized or mimed. The latest study — published in Nature Human Behaviour on 13 May1 — is the first to decode words spoken entirely internally, by recording signals from individual neurons in the brain in real time. “It's probably the most advanced study so far on decoding imagined speech,” says Silvia Marchesotti, a neuroengineer at the University of Geneva, Switzerland. “This technology would be particularly useful for people that have no means of movement any more,” says study co-author Sarah Wandelt, a neural engineer who was at the California Institute of Technology in Pasadena at the time the research was done. “For instance, we can think about a condition like locked-in syndrome.” The researchers implanted arrays of tiny electrodes in the brains of two people with spinal-cord injuries. They placed the devices in the supramarginal gyrus (SMG), a region of the brain that had not been previously explored in speech-decoding BCIs. © 2024 Springer Nature Limited

Keyword: Brain imaging; Language
Link ID: 29302 - Posted: 05.14.2024

By Angie Voyles Askham The ability of amphibians to metamorphosize and, in some cases, regenerate limbs and even brain tissue raises puzzling yet fundamental questions about how a nervous system wires itself up. For example, if a frog’s legs don’t exist when its brain begins to develop—those limbs later replace its tadpole tail—how are the neural connections maintained such that, once the legs take shape, a frog can move them? “How many connections are there between the spinal cord and the brain? How do they change over metamorphosis?” asks Lora Sweeney, assistant professor at the Institute of Science and Technology Austria. To find out, Sweeney and her colleagues decided to screen a panel of adeno-associated viruses (AAVs) in two species of frog and a newt. These viruses are commonly used to genetically manipulate brain cells in rodents and monkeys, but they have not been proven useful in amphibian experiments. With the right techniques, most common AAVs can deliver genes to amphibian cells through a process called transduction, according to Sweeney’s unpublished results, though the most effective viruses vary by species. These amphibian-friendly AAVs can be used to trace neuronal connections and track groups of neurons born at the same time, the new work shows. And a subset of these same AAVs can also transduce cells in axolotls, newts’ fuzzy-gilled Mexican cousins, according to another preprint from an independent team. Both preprints were posted on bioRxiv in February. “It’s a big game-changer,” says Helen Willsey, assistant professor of psychiatry at the University of California, San Francisco, who was not involved in either study but works with amphibian models. “It opens up a lot of doors for new experiments.” Other researchers had previously tried to get AAVs to transduce cells in frogs and fish, with little success. © 2024 Simons Foundation

Keyword: Brain imaging; Evolution
Link ID: 29267 - Posted: 04.24.2024