Latest news with #hippocampus
Yahoo
07-07-2025
- Health
- Yahoo
Brain's Memory Center Never Stops Making Neurons, Study Confirms
Though it's now clear humans continue to grow new brain cells throughout their entire lives, debate persists over whether this applies to specific areas involved with memory. Previous studies have made the case for and against the existence of neurogenesis in hippocampus beyond childhood. A new study now offers some of the clearest evidence yet that this crucial memory-forming region does form fresh neurons well into adulthood. The study is the work of researchers from the Karolinska Institute and the Chalmers University of Technology in Sweden, and looks specifically at the dentate gyrus section of the hippocampus, the part of the brain that acts as a key control center for emotions, learning, and storing episodic memories. Related: "This gives us an important piece of the puzzle in understanding how the human brain works and changes during life," says molecular biologist Jonas Frisén. Confirmation that humans can form new neurons in the hippocampus through life (as several other animals can) would inform a whole host of other scientific investigations, from how adults learn new skills to what happens to the brain as it deteriorates in old age. The team used RNA analysis to identify functions of brain cells in samples collected from people up to age 78, finding that some neurons were geared to function as neural progenitor cells (NPCs), which generate new nerve cells. The researchers also found similarities between human NPCs and those in mice, pigs, and monkeys. Through a process of machine learning, the researchers could also group cells according to their development, from their initial 'blank slate' stem cell characterization to being an immature neuron in the process of dividing. The results address questions raised by earlier studies (including one from some of the same researchers), which determined that new neurons were present in the human brain without being able to confirm exactly how they'd got there. "We have now been able to identify these cells of origin, which confirms that there is an ongoing formation of neurons in the hippocampus of the adult brain," says Frisén. By studying such a wide range of ages, the researchers confirmed neurogenesis keeps happening in the hippocampus throughout our adult lives – albeit at a slower rate, generally speaking, as we get older. It's also important to note that the analysis revealed different rates of neurogenesis in different people. That might point to differences in brain plasticity that affect learning, personality, and disease risk, but that's something that future studies will need to look at. One hypothesis is that certain brain conditions might be affected by how quickly fresh new neurons can be produced – some of the subjects in this study had a history of psychiatric or neurological diseases – but again this wasn't something that the researchers looked at directly, so follow-up studies will be needed. "Our research may also have implications for the development of regenerative treatments that stimulate neurogenesis in neurodegenerative and psychiatric disorders," says Frisén. The research has been published in Science. Pomegranates Could Limit Risks From Controversial Sports Supplement OCD's Origins Might Not Lie in The Brain Like We Thought The News Cycle Is a Stress Monster. But There's a Healthy Way to Stay Informed.
Yahoo
04-07-2025
- Health
- Yahoo
Human brains keep growing neurons even in old age, study finds for first time
For decades, scientists believed the human brain stopped producing new neurons after childhood. This long-held view painted the adult brain as a fixed organ, incapable of generating fresh cells in the very region responsible for memory and learning. But a landmark new study turns that dogma on its head, offering the clearest evidence yet that adult humans continue to form new neurons well into the old age. A team of researchers from Karolinska Institutet in Sweden has identified and tracked the formation of new neurons in the hippocampus, a region critical for memory, learning, and emotional regulation. In 2013, a team of researchers led by Professor Jonas Frisén made headlines with a study showing that new neurons can form in the hippocampus of adult humans. They used carbon-14 dating in DNA extracted from brain tissue to pinpoint when individual cells were created, providing rare evidence of adult neurogenesis. But while the study proved that new neurons could exist, it did not answer where these neurons come from. Until now, scientists lacked direct proof that the neural progenitor cells were present and actively dividing in the adult human brain. 'We have now been able to identify these cells of origin, which confirms that there is an ongoing formation of neurons in the hippocampus of the adult brain,' said Frisén. In the new study, the team analyzed post-mortem brain tissue from individuals ranging in age from infancy to 78 years to discover that neural progenitor cells—precursors to fully developed neurons—not only exist in the adult brain but are also actively dividing. The study used advanced techniques like single-nucleus RNA sequencing to map gene activity in individual brain cell nuclei. Combined with flow cytometry and machine learning, the approach allowed researchers to identify various stages of neuronal development, ranging from stem-like cells to immature, still-dividing neurons. To visualize where these new neurons were forming, the scientists employed RNAscope and Xenium, two powerful spatial transcriptomics tools. These confirmed that the cell formation was happening in the dentate gyrus, a part of the hippocampus linked to learning, cognitive flexibility, and the encoding of new memories. The findings reveal that adult human neural progenitor cells closely resemble those seen in mice, pigs, and monkeys, though some gene activity patterns differ between species. What's especially intriguing is the variability between individuals. While some adults had abundant neural progenitor cells, others had very few, raising new questions about what factors might influence adult neurogenesis. 'This gives us an important piece of the puzzle in understanding how the human brain works and changes during life,' Frisén explained. 'Our research may also have implications for the development of regenerative treatments that stimulate neurogenesis in neurodegenerative and psychiatric disorders.' The findings could also pave the way for new regenerative therapies for neurodegenerative and psychiatric conditions, potentially helping to restore or enhance brain function by stimulating neuron formation in targeted ways. The groundbreaking study has been published in the journal Science.
Yahoo
04-07-2025
- Health
- Yahoo
Can adults make new brain cells? New study may finally settle one of neuroscience's greatest debates
When you buy through links on our articles, Future and its syndication partners may earn a commission. Researchers say they have found clear evidence that the human brain can keep making new neurons well into adulthood, potentially settling decades of controversy. This new neuron growth, or "neurogenesis," takes place in the hippocampus, a critical part of the brain involved in learning, memory and emotions. "In short, our work puts to rest the long-standing debate about whether adult human brains can grow new neurons," co-lead study author Marta Paterlini, a researcher at the Karolinska Institute in Stockholm, told Live Science in an email. Other experts agree that the work makes a strong case for adult neurogenesis. While a single study does not constitute absolute proof, "this is strong evidence in support of the idea" that stem cells and precursors to new neurons exist and are proliferating in the adult human brain, said Dr. Rajiv Ratan, CEO of the Burke Neurological Institute at Weill Cornell Medicine, who was not involved in the study. "This is a perfect example of great science teeing up the ball for the clinical neuroscience community," he told Live Science. Related: Babies' brain activity changes dramatically before and after birth, groundbreaking study finds The researchers combined advanced techniques, including single-nucleus RNA sequencing and machine learning, to sort and examine brain tissue samples from international biobanks, they reported in a paper published July 3 in the journal Science. RNA, a cousin of DNA, reflects genes that are "switched on" inside cells, while machine learning is a type of artificial intelligence often used to crunch huge datasets. Since the 1960s, researchers have known that mice, rats and some nonhuman primates make new brain cells in the dentate gyrus, part of the hippocampus, throughout life. But getting quality brain tissue samples from adult humans is extremely challenging. "Human tissue comes from autopsies or surgeries, so how it's handled — how long before it's fixed in preservative, which chemicals are used, how thin the slices are — can hide those newborn cells," Paterlini said. Employing new technologies enabled the team to overcome this challenge. They analyzed more than 400,000 individual nuclei of hippocampus cells from 24 people, and in addition, looked at 10 other brains using other techniques. The brains came from people ages 0 to 78, including six children and four teens. Using two cutting-edge imaging methods, the team mapped where new cells sat in the tissue. They saw groups of dividing precursor cells sitting right next to the fully formed neurons, in the same spots where animal studies have shown that adult stem cells reside. "We didn't just see these dividing precursor cells in babies and young kids — we also found them in teenagers and adults," Paterlini said. "These include stem cells that can renew themselves and give rise to other brain cells." The newer technologies enabled the researchers to detect the new brain cells at various stages of development and conduct research that wouldn't have been possible a few years ago, Ratan added. The team also used fluorescent tags to mark the proliferating cells. This enabled them to build a machine learning algorithm that identified the cells that they knew would turn into neurogenic stem cells, based on past rodent studies. This was a "clever approach" for tackling the challenges of studying brain-cell formation in adolescents and adults, Ratan said. As expected, the brains of children produced more new brain cells than the brains of adolescents or adults did. Meanwhile, nine out of 14 adult brains analyzed with one technique showed signs of neurogenesis, while 10 out of 10 adult brains analyzed with a second technique bore new cells. Regarding the few brains with no new cells, Paterlini said it's too soon to draw conclusions about the disparity between adult brains with evidence of new cells and those without. RELATED STORIES —How much of your brain do you need to survive? —You're born with most of your neurons — but the brain makes some mysterious new ones in adulthood —Brain aging accelerates dramatically around age 44 — could ketone supplements help? Next, the researchers could explore whether the adults who produced new brain cells did so in response to a neurological disease, such as Alzheimer's, or whether adult neurogenesis is a sign of good brain health, said Dr. W. Taylor Kimberly, chief of neurocritical care at Massachusetts General Brigham, who was not involved in the study. "They were able to find these needles in a haystack," Kimberly told Live Science. "Once you detect them and learn about them and understand their regulation," scientists can research how to track the precursor cells through time and see how their presence relates to disease, he said. He envisioned comparing patients who have dementia to "super agers" who are cognitively resilient in old age. If the link between neurogenesis and disease can be uncovered, perhaps that could open the door to treatments. "Although the precise therapeutic strategies in humans are still under active research," Paterlini said, "the very fact that our adult brains can sprout new neurons transforms how we think about lifelong learning, recovery from injury and the untapped potential of neural plasticity."
Yahoo
03-07-2025
- Health
- Yahoo
Even old brains can make new neurons, study suggests
Your body is constantly generating new cells. In your digestive tract, the colon's lining turns over every five to seven days. Your red blood cells replace themselves every few weeks, skin cells about once a month. But certain organs are a big exception. Contrary to popular belief, we are not biological Theseus' ships, reconstructing ourselves entirely from fresh building blocks every seven years. Most of your neurons, the cells that fast-track information across the brain, spine, and sensory organs, have the same lifespan as you do. Until the late 20th century, the prevailing view in neuroscience was that, past childhood, humans stop making neurons, brain-wide. What we have in adolescence, is what we get, and all we can do is lose cells or reorganize them. However, the latest research adds to a mounting body of evidence finding that the timeline of neuron generation isn't so clear-cut. In at least two parts of the brain, a subset of neuroscientists believe that neurons may continue to form throughout life–the hippocampus and the ventral striatum. In the hippocampus, a critical brain region for learning and memory, new cells emerge in some people into late adulthood, according to a study published July 3 in the journal Science. The findings tip the scales in a still-active debate over how our brains continue to develop throughout life. A better understanding of adult neurogenesis (the formation of new neurons), and a firm answer to if and where it occurs, could help improve treatments for neurological diseases as well as normal aging. [ Related: Scientists mapped every neuron of an adult animal's brain for the first time. ] Past research in rodents, pigs, and monkeys has shown that neurogenesis does happen in these other mammals, throughout life. Birds do it too. Yet based on other noted structural and developmental differences in the human brain, some scientists argue that our species is unique and lacks the lifelong neurogenesis that might interrupt complex, streamlined brain function. (New neurons may sound great, but too much activity and connectivity can cause chaos.) And it's difficult to get a clear answer. It's a major technical challenge to pin down new brain cells in humans because you can't readily see through living skulls at the cellular level. Researchers largely have to rely on scarce brain tissue collected via surgery on those with medical conditions like epilepsy or tissue donated by the deceased. With this new study, 'I think they used really strong tools,' Mercedes Paredes, a neurologist and developmental neuroscientist at University of California, San Francisco, tells Popular Science. Paredes was not involved in the research, but has previously found contrasting results in her own lab. The new work, she says, is a 'good starting point' for applying novel methods to the brain and deciphering what types of cells are truly present. Other studies of potential adult neurogenesis have looked at protein and immune signatures in brain tissues to determine if, where, and how often new neurons are being formed. They've come to conflicting conclusions, with some (like Paredes' 2018 work) failing to identify the cells that other researchers report seeing. There've also been a few studies that rely on carbon dating to ascertain the age of neurons, which find young cells in adults. However, none of these methods have, so far, reliably pinpointed the stem cells or progenitors capable of yielding fresh neurons–leaving room for doubt. The new study seems to address this previously unresolved point. It's the 'missing link' of neurogenesis, Jonas Frisén, senior study author and a developmental biologist and stem cell researcher at Karolinska Institutet in Stockholm, tells Popular Science. To find that missing link, Frisén and his co-authors surveyed the scientific literature to compile a list of genes that are likely active in hippocampal neurogenesis. Then, they confirmed those gene markers (largely from animal studies) by comparing them to RNA sequences found in brain samples from six deceased, child and infant donors. Next, the team sequenced RNA from mitochondria in the brain tissue from 19 people between the ages of 13 and 78. They used three different machine learning algorithms to assess those sequences and identify likely intermediate, forming neural cells. The scientists validated their machine learning outputs by applying the same tools to datasets from mice and adult human cortex cells, and reported a false positive rate of just 0.37 all of their analyses, they identified 354 of cells out of hundreds of thousands across their 19 samples that appeared to be precursors to new neurons, including dozens of stem cells and neuroblasts from adults. The cells weren't distributed uniformly, only showing up in half the adolescent samples and five of the 14 adult samples. However, whether or not the cells were present didn't seem to wholly correlate with age or documented disease. One of the adults with the highest number of neurogenesis-related cells present was a 58-year-old with no known pathology, per the study.'We nailed down active neurogenesis in the adult human brain,' Marta Paterlini, a neuroscientist at Karolinska Institutet, tells Popular Science. She co-led the new work over eight years alongside her colleague Ionut Dumitru, who focused on the machine learning side. 'We are confident in our data,' Paterlini says. 'We would like to put an end to the controversy.' Still, not everyone in the field agrees that the cells identified in this study are indisputably emerging adult neurons. 'When I first heard about this study, I was excited. It's the sort of approach you would want to use to ID rare subtypes,' Shawn Sorrells, a neuroscientist at the University of Pittsburgh who co-authored the 2018 study with Paredes, tells Popular Science. But, after a closer look, he was 'disappointed by how few cells they found,' and in his view, there's an alternate potential explanation. 'The most likely conclusion is that the cells they are looking for are rare or nonexistent in most people. The other possibility is that the cells they claim are adult neural stem cells are associated with a disease process in these individuals or some other cell type altogether.' The human brain is full of cells that do divide and replicate throughout life called glial cells. These are the supportive and connective cells that enable neurons to do the job of conveying nerve signals. Glial cells are neurons' pit crew. It's possible that, in their efforts to identify neurons in progress, the study authors may have inadvertently included some glial stem cells in their analysis, Sorrells suggests. [ Related: New human brain atlas is the most detailed one we've seen yet. ] Both Sorrells and Paredes believe more research is needed to confirm the new study's conclusions. Direct, morphological comparisons between human and animal cells could boost the findings, says Paredes. Sorrells suggests we'll need more advanced brain imaging techniques to really resolve the issue. 'Following the same cells over time to see how they develop. That will be the best evidence for neurogenesis,' he explains, though notes that's currently not possible. And so, the science presses on. If, as the new research indicates, some healthy humans do continue to make neurons inside their hippocampuses for life, it could have major implications for psychiatric and neurodegenerative diseases like Alzheimers, where animal studies indicate a dearth of new cells plays a role. It could also aid in our ability to understand and maximize healthy aging and neuroplasticity, Frisén says. Perhaps down the line, adult neural stem cells could be used to help people recover after brain trauma, Paterlini suggests. 'The lab is working on regenerative medicine, so we will keep going on this.' And maybe all their effort will manage to change minds about how much human minds can change.
