網路城邦
回本城市首頁 時事論壇
市長:胡卜凱  副市長:
加入本城市推薦本城市加入我的最愛訂閱最新文章
udn城市政治社會政治時事【時事論壇】城市/討論區/
討論區知識和議題 字體:
看回應文章  上一個討論主題 回文章列表 下一個討論主題
大腦神經學:一般研究 – 開欄文
 瀏覽1,239|回應5推薦1

胡卜凱
等級:8
留言加入好友
文章推薦人 (1)

胡卜凱

我對大腦神經學的興趣始自上一世紀80年代。

我最早的求知動機在於回答「行為是否需要準則」和(如果需要)「行為準則是什麼」這兩個問題。後來逐漸領悟到:這兩個問題其實是「決策判定」的問題。做為工程師,我自然了解「決策」的基礎在「知識」。從而,我的讀書範圍從倫理學和社會學擴充到「認識論」。1982前後我讀了第一本介紹「認知科學」的書。自此,大腦神經學成為我主要的閱讀對象。從2000年以後,我立論的基本假設都包含我對它的粗淺了解。《唯物人文觀(2006)則是我第一次嘗試整合我對大腦神經學與人文/社會科學兩個領域的了解。

最近我起了整合本城市討論/報導過各個重要議題的念頭;大腦神經學自然在列。等我完成手頭兩篇討論「文化」的文章後,我會開始討論「意識」。

本文於 修改第 3 次
回應 回應給此人 推薦文章 列印 加入我的文摘

引用
引用網址:https://city.udn.com/forum/trackback.jsp?no=2976&aid=7216219
 回應文章
記憶和DNA -- Max Kozlov
推薦0


胡卜凱
等級:8
留言加入好友

 
如果這篇大腦神經學研究通俗報導中研究者的詮釋成立度很高,此文作者對研究結果報導的可信度也很高,相信此研究能幫助我們進一步了解「記憶」、「意識」、以及和「大腦神經」相關的種種症狀(如作者提及的阿茲海默症)

我不清楚這篇通俗報導所說的大腦DNA是否具有「可遺傳性」;如果有,或許它也能解釋「似曾相識」現象。甚至可以解釋:「龍生龍,鳳生鳳,老鼠生的兒子只學得會打洞」現象。

索引


engram記憶實體,記憶痕跡
hippocampus
海馬迴,大腦內貌似海馬的區塊
inflammation
發炎
organelle:細胞內構成該細胞的次級結構,具有特定功能
pathogens:病原體
plasticity, neural
(大腦神經網路連接的)可塑性


Memories are made by breaking DNA — and fixing it

Nerve cells form long-term memories with the help of an inflammatory response, study in mice finds.

Max Kozlov, 03/27/24

Neurons (shown here in a coloured scanning electron micrograph) mend broken DNA during memory formation. Credit: Ted Kinsman/Science Photo Library (請至原網頁查看圖片)

When a long-term memory forms, some brain cells experience a rush of electrical activity so strong that it snaps their DNA. Then, an inflammatory response kicks in, repairing this damage and helping to cement the memory, a study in mice shows.

The findings, published on 27 March in Nature1, are “extremely exciting”, says Li-Huei Tsai, a neurobiologist at the Massachusetts Institute of Technology in Cambridge who was not involved in the work. They contribute to the picture that forming memories is a “risky business”, she says. Normally, breaks in both strands of the double helix DNA molecule are associated with diseases including cancer. But in this case, the DNA damage-and-repair cycle offers one explanation for how memories might form and last.

It also suggests a tantalizing possibility: this cycle might be faulty in people with neurodegenerative diseases such as Alzheimer’s, causing a build-up of errors in a neuron’s DNA, says study co-author Jelena Radulovic, a neuroscientist at the Albert Einstein College of Medicine in New York City.

Inflammatory response

This isn’t the first time that DNA damage has been associated with memory. In 2021, Tsai and her colleagues showed that double-stranded DNA breaks are widespread in the brain, and linked them with learning2.

To better understand the part these DNA breaks play in memory formation, Radulovic and her colleagues trained mice to associate a small electrical shock with a new environment, so that when the animals were once again put into that environment, they would ‘remember’ the experience and show signs of fear, such as freezing in place. Then the researchers examined gene activity in neurons in a brain area key to memory — the hippocampus. They found that some genes responsible for inflammation were active in a set of neurons four days after training. Three weeks after training, the same genes were much less active.

The team pinpointed the cause of the inflammation: a protein called TLR9, which triggers an immune response to DNA fragments floating around the insides of cells. This inflammatory response is similar to one that immune cells use when they defend against genetic material from invading pathogens, Radulovic says. However, in this case, the nerve cells were responding not to invaders, but to their own DNA, the researchers found.

TLR9 was most active in a subset of hippocampal neurons in which DNA breaks resisted repair. In these cells, DNA repair machinery accumulated in an organelle called the centrosome, which is often associated with cell division and differentiation. However, mature neurons don’t divide, Radulovic says, so it is surprising to see centrosomes participating in DNA repair. She wonders whether memories form through a mechanism that is similar to how immune cells become attuned to foreign substances that they encounter. In other words, during damage-and-repair cycles, neurons might encode information about the memory-formation event that triggered the DNA breaks, she says.

When the researchers deleted the gene encoding the TLR9 protein from mice, the animals had trouble recalling long-term memories about their training: they froze much less often when placed into the environment where they had previously been shocked than did mice that had the gene intact. These findings suggest that “we are using our own DNA as a signalling system” to “retain information over a long time”, Radulovic says.  

Fitting in

How the team’s findings fit with other discoveries about memory formation is still unclear. For instance, researchers have shown that a subset of hippocampal neurons known as an engram are key to memory formation3. These cells can be thought of as a physical trace of a single memory, and they express certain genes after a learning event. But the group of neurons in which Radulovic and her colleagues observed the memory-related inflammation are mostly different from the engram neurons, the authors say.

Tomás Ryan, an engram neuroscientist at Trinity College Dublin, says the study provides “the best evidence so far that DNA repair is important for memory”. But he questions whether the neurons encode something distinct from the engram — instead, he says, the DNA damage and repair could be a consequence of engram creation. “Forming an engram is a high-impact event; you have to do a lot of housekeeping after,” he says.

Tsai hopes that future research will address how the double-stranded DNA breaks happen and whether they occur in other brain regions, too.

Clara Ortega de San Luis, a neuroscientist who works with Ryan at Trinity College Dublin, says that these results bring much-needed attention to mechanisms of memory formation and persistence inside cells. “We know a lot about connectivity” between neurons “and neural plasticity, but not nearly as much about what happens inside neurons”, she says.

doi: https://doi.org/10.1038/d41586-024-00930-y


Read the related News & Views: ‘Innate immunity in neurons makes memories persist.

UPDATES & CORRECTIONS

Correction 27 March 2024: An earlier version of this story indicated that broken DNA accumulated in the centrosome. It is DNA repair machinery that accumulates in that organelle.

References

Jovasevic, V. et al. Nature 628, 145–153 (2024). Article Google Scholar 
Stott, R. T., Kritsky, O. & Tsai, L.-H. PLoS ONE 16, e0249691 (2021). Article PubMed Google Scholar 
Josselyn, S. A. & Tonegawa, S. Science 367, eaaw4325 (2020).

Article Google Scholar
Download referencesReprints and permissions

相關閱讀

How to see a memory
Flashes of light show how memories are made


本文於 修改第 1 次
回應 回應給此人 推薦文章 列印 加入我的文摘
引用網址:https://city.udn.com/forum/trackback.jsp?no=2976&aid=7225613
《停經對女人大腦的影響》讀後
推薦1


胡卜凱
等級:8
留言加入好友

 
文章推薦人 (1)

胡卜凱

上一篇文章報導20%婦女在停經後可能導致智力衰退。停經期的症狀和造成阿茲海默病的原因有類似之處

文章後半段是對保持大腦和智力健康的建議

1)  補充賀爾蒙
2)  經常運動
3)  健康飲食習慣

作者引用一位醫生的話:在社會習俗洗腦下,大多數中年婦女總是把自己的幸福放在其他人之後。言外之意是:一個人要先把自己照顧好,才有餘力招呼別人

我一向認為對精神(心理)和大腦疾病症狀及其原因的研究除了有利臨床治療外也能幫助我們了解大腦運作的機制與過程。最終讓人類解開「意識」這個謎團。

本文於 修改第 1 次
回應 回應給此人 推薦文章 列印 加入我的文摘
引用網址:https://city.udn.com/forum/trackback.jsp?no=2976&aid=7217600
停經對女人大腦的影響-Alisha Haridasani Gupta
推薦0


胡卜凱
等級:8
留言加入好友

 
How Menopause Changes the Brain

Neurological changes and menopausal symptoms are linked to dementia for some. Here’s what to know.

, 11/21/23


Neurological changes and menopausal symptoms are linked to dementia for some. (Sonia Pulido/The New York Times) Ñ FOR EDITORIAL USE ONLY WITH NYT STORY MENOPAUSE BRAIN BY ALISHA HARIDASANI GUPTA FOR NOV. 23, 2023. ALL OTHER USE PROHIBITED. Ñ (NYT) --
請至原網頁參閱相關圖片

Across the U.S., roughly 6 million adults 65 and older have Alzheimer’s disease. Almost two-thirds of them are women — a discrepancy that researchers have long attributed to genetics and women’s longer life spans, among other reasons. But there is growing consensus that menopause may also be an important risk factor for the development of dementia later in life.

Women going through the life phase, which is clinically defined as the end of fertility, face as many changes in the brain as in the ovaries, said Dr. Lisa Mosconi, a neuroscientist and director of the Women’s Brain Initiative at Weill Cornell Medicine. While the vast majority of women will weather these changes without long-term health consequences, about 20% will develop dementia in the decades that follow.

The female brain is rich in estrogen receptors, particularly in regions that control memory, mood, sleep and body temperature, all of which “work beautifully when estrogen is high and consistent,” Mosconi said. Estrogen is also vital for the brain’s ability to defend itself against aging and damage.

The characteristic decline in estrogen during menopause not only alters the functioning in some brain regions, she said, it is also thought to change the brain’s structure; scans show reduced volume in menopausal brains compared to male brains of the same age and to those of pre-menopausal women.

These neurological changes may be responsible for some menopausal symptoms, including hot flashes, mood disruption and a mild, usually temporary decline in memory and cognition.

They also resemble changes in the brain that precede dementia, Mosconi said. “Some of the brain regions that are impacted by menopause are also some of the regions impacted by Alzheimer’s disease,” she said, but the link between the two is not fully understood.

The symptoms of menopause themselves, such as lack of sleep and hot flashes, have been linked to dementia too. A study published last year found that hot flashes were associated with an increased amount of tiny lesions in the brain, which are a sign of declining brain health, said Dr. Pauline Maki, a professor of psychiatry and director of the Women’s Mental Health Research Program at the University of Illinois at Chicago and co-author of the study. A more recent study determined that hot flashes during sleep were associated with an increase in blood-based Alzheimer’s biomarkers that serve as early indicators of the disease.

While this research sounds alarming, most women’s brains and cognitive function stabilize after the menopause transition, Maki said.

“Consider how many women go through menopause — every woman, right? And 80% of them will not get dementia,” she said. “We can’t catastrophize this universal transition.”

Beyond that, there are things you can do to bolster your health and cognition in the face of declining estrogen.

Three Steps to Protect Your Brain

Several studies have found that up to 40% of dementia cases could be prevented, said Dr. Jessica Caldwell, director of the Women’s Alzheimer’s Movement Prevention Center at the Cleveland Clinic in Las Vegas. And a few lifestyle changes in midlife, including quitting smoking, reducing alcohol intake, sleeping better and remaining mentally and socially active, aid in prevention.

But for women in menopause, experts say that three things in particular are likely to have the most impact by addressing both the short-term symptoms as well as the long-term risk of dementia.

Hormone Therapy, Timed Right

For decades, researchers were concerned that the hormone therapy used to treat menopause symptoms was associated with an increased risk of developing dementia in older women. But recent studies, including one published last month that reviewed the findings of over 50 studies, look more closely at the timing of the therapy and suggest a more nuanced picture: Hormone therapy that was started around the time when menopausal symptoms began was associated with a reduced risk of Alzheimer’s disease and dementia. Other studies have found that hormone therapy had no effect on dementia and Alzheimer’s risk, Maki said, but these treatments are effective at addressing hot flashes and night sweats as well as improving quality of life, all of which are “important determinants of brain health,” she said.

Consistent Exercise

Physical inactivity presents a greater risk for neurodegenerative diseases in women than in men, Caldwell said. “We know that physical inactivity is a risk factor for dementia. And women throughout their lives, on average, are twice as likely to be physically inactive than men,” she said.

A 2018 study that followed almost 200 middle-aged women for 44 years found that the greater their fitness level at the start of the study, the lower their risk of developing dementia later in life. And Mosconi found that brain scans of physically active middle-aged women had fewer Alzheimer’s biomarkers compared to their sedentary counterparts.

A Healthy Diet

In recent years, researchers have found that certain diets, like the Mediterranean diet and the fairly similar MIND diet, which prioritize vegetables, fruits, whole grains, lean proteins and healthy fats, are associated with a reduced risk of dementia in both men and women. The Mediterranean diet in particular seems to be a protective tool, even for women with a genetic risk for Alzheimer’s disease, Mosconi said. And there may be a specific added benefit of these plant-rich diets for women: Preliminary research suggests that certain gut bacteria — which are nourished by a plant-rich diet — might help balance estrogen levels in the body.

Many of these lifestyle changes take time that many middle-aged women feel they don’t have, Caldwell said.

“We are expected by society to put ourselves after everybody else, whether that’s kids, parents or spouses, and we need to keep ourselves on the priority list,” she said. “Because if we don’t do these types of health-maintenance behaviors, we will not have the healthy brain aging we want.”

c.2023 The New York Times Company

索引

dementia:(老年)智力衰退
estrogen
雌激素,又稱女性動情素
nuanced:細緻入微的,精細分類的

本文於 修改第 2 次
回應 回應給此人 推薦文章 列印 加入我的文摘
引用網址:https://city.udn.com/forum/trackback.jsp?no=2976&aid=7217599
昏過去的原因 ------ Miryam Naddaf
推薦1


胡卜凱
等級:8
留言加入好友

 
文章推薦人 (1)

胡卜凱

我今年8月身體微恙有一天半夜起來如廁時昏了過去但沒多長就醒過來。走了幾步後又昏了過去;也是沒多長就醒過來。兩次症狀和下文描述的一樣;同樣情況十幾、二十年前也發生過一次。

十月中我到心臟科做了整套檢查,醫生說我的心臟沒有問題。前兩天剛好看到這篇文章,和各位分享。如果碰到類似狀況,應該盡快做檢查;但不必驚慌或自己嚇自己。


What causes fainting? Scientists finally have an answer

Mouse experiments reveal the brain-heart connections that cause us to rapidly lose consciousness — and wake up moments later.

Miryam Naddaf, 11/01/23

Whether as a result of heat, hunger, standing for too long, or merely at the sight of blood or needles, 40% of people faint at least once in their lifetime.

But exactly what causes these brief losses of consciousness — which researchers call ‘syncope’ — has remained a mystery for cardiologists and neuroscientists for a long time.

Now, researchers have discovered a neural pathway, which involves a previously undiscovered group of sensory neurons that connect the heart to the brainstem. The study, published in Nature on 1 November
1, shows that activating these neurons made mice became immobile almost immediately while displaying symptoms such as rapid pupil dilation and the classic eye-roll observed during human syncope.

The authors suggest that this neural pathway holds the key to understanding fainting, beyond the long-standing observation that it results from reduced blood flow in the brain. “There is blood flow reduction, but at the same time there are dedicated circuits in the brain which manipulate this,” says study co-author Vineet Augustine, a neuroscientist at the University of California, San Diego.

“The study of these pathways could inspire new treatment approaches for cardiac causes of syncope,” says Kalyanam Shivkumar, a cardiologist at the University of California, Los Angeles.

Novel neurons

The mechanisms that control how and why people faint have long puzzled scientists, partly because researchers tend to focus on studying either the heart or the brain in isolation. But the authors of the study developed novel tools to show how these two systems interact.

Using single-cell RNA sequencing analysis of the nodose ganglia, an area in the vagus nerve (which connects the brain to several organs, including the heart), the team identified a group of sensory neurons that express a type of receptor involved in the contraction of small muscles within blood vessels that causes them to constrict.

These neurons, called NPY2R VSNs, are distinct from other branches of the vagus nerve that connect to the lungs or the gut. They instead form branches within the lower,muscular parts of the heart, the ventricles, and connect to a distinct area in the brainstem called area postrema.

Using a new technique that combines high-resolution ultrasound imaging with optogenetics — a way of controlling neuron activity using light — the researchers stimulated the NPY2R VSNs in mice while monitoring their heart rate, blood pressure, respiration and eye movements. This approach allowed the team to manipulate specific neurons and visualise the heart in real time. “This was not possible before, because you needed to figure out the identity of these neurons,” says Augustine.

When the NPY2R VSNs were activated, mice that had been freely moving around fainted with a few seconds. While passed out, the mice displayed similar symptoms to humans during syncope, including rapid pupil dilation and eyes rolling back in their sockets, as well as reduced heart rate, blood pressure, breathing rate and blood flow to the brain.

“We now know that there are receptors in the heart that when made to fire, will shut down the heart,” says Jan Gert van Dijk, clinical neurologist at Leiden University Medical Centre in the Netherlands.

In humans, syncope is usually followed by a rapid recovery. “Neurons in the brain are very much like extremely spoiled children. They need oxygen and they need sugar, and they need them now,” says Dijk. “They stop working very quickly if you derive them off oxygen or glucose.”

These nerve cells begin to die after about 2 to 5 minutes without oxygen, but syncope typically lasts only 20 to 40 seconds. “If you add oxygen again, they'll simply resume their work and do so just as quickly,” says Dijk.

Brain activity

To better understand what happens inside the brain during syncope, the researchers recorded the activity of thousands of neurons from various brain regions in mice using electrodes. They found that activity decreased in all areas of the brain except one specific region in the hypothalamus known as PVC.

When the authors inhibited/blocked the activity of PVC, the mice experienced longer fainting episodes, while its stimulation caused the animals to wake up and start moving again. The team suggests that a coordinated neural network that includes NPY2R VSNs and PVC regulates fainting and the rapid recovery that follows.

“Coming from a clinical standpoint, this is all very exciting,” says Richard Sutton, clinical cardiologist at Imperial College London. The discovery of NPY2R VSNs “doesn't answer all questions immediately”, he adds, “but I think it could answer with future research almost everything.”

For “questions that cardiologists have been asking for decades, now you can bring in a neuroscience perspective and really see how the nervous system controls the heart”, says Augustine.

The next big question is studying how these neurons are triggered, says Dijk. “It's been one of the biggest riddles of my entire career.”

doi: https://doi.org/10.1038/d41586-023-03450-3

References

Lovelace, J. W. et al. Nature https://doi.org/10.1038/s41586-023-06680-7 (2023).


本文於 修改第 2 次
回應 回應給此人 推薦文章 列印 加入我的文摘
引用網址:https://city.udn.com/forum/trackback.jsp?no=2976&aid=7216234
最新的大腦結構圖 -- Gemma Conroy
推薦1


胡卜凱
等級:8
留言加入好友

 
文章推薦人 (1)

胡卜凱

This is the largest map of the human brain ever made

Researchers catalogue more than 3,000 different types of cell in our most complex organ.

Gemma Conroy, 10/12/23

Researchers have created the largest atlas of human brain cells so far, revealing more than 3,000 cell types — many of which are new to science. The work, published in a package of 21 papers today in ScienceScience Advances and Science Translational Medicine, will aid the study of diseases, cognition and what makes us human, among other things, say the authors.

The enormous cell atlas offers a detailed snapshot of the most complex known organ. “It’s highly significant,” says Anthony Hannan, a neuroscientist at the Florey Institute of Neuroscience and Mental Health in Melbourne, Australia. Researchers have previously mapped the human brain using techniques such as magnetic resonance imaging, but this is the first atlas of the whole human brain at the single-cell level, showing its intricate molecular interactions, adds Hannan. “These types of atlases really are laying the groundwork for a much better understanding of the human brain.”

The research is part of the US National Institutes of Health’s Brain Research through Advancing Innovative Neurotechnologies InitiativeCell Census Network (BICCN), a collaboration between hundreds of scientists. The programme’s goals include cataloguing brain cell types across humans, non-human primates and mice to improve understanding of the cellular mechanisms behind poorly understood brain disorders. The data from the 21 studies have been made publicly available on the Neuroscience Multi-omic Archive online repository.

Cellular menagerie

Kimberly Siletti, a neuroscientist now at the University Medical Center Utrecht in the Netherlands, and her team laid the cornerstone for the atlas by sequencing the RNA of more than 3 million individual cells from 106 locations covering the entire human brain, using tissue samples from three deceased male donors1. They also included one motor cortex dissection from a female donor that had been used in previous studies. Their analysis documented 461 broad categories of brain cell that included more than 3,000 subtypes. “I was surprised at how many different cell types there were,” says Siletti.

Neurons — cells in the brain and nervous system that send and receive signals — varied widely in different parts of the brain, suggesting different functions and developmental histories. The mix of neurons and other cell types also differed across each region; some cells were only found in specific locations. The brainstem — a relatively under-studied structure connecting the brain to the spinal cord — harboured a particularly high number of neuron types, says study co-author Sten Linnarsson, a molecular systems biologist at the Karolinska Institute in Stockholm, Sweden. “One of the big surprises here is how incredibly complex the brainstem is.”

Other studies drilled into the mechanisms of gene regulation and expression in different cells. Joseph Ecker, a molecular biologist at the Salk Institute for Biological Studies in La Jolla, California, and his colleagues investigated the brain through an epigenetic lens using tissue samples from the same three donors2. They analysed chemical markers that switch genes on or off in more than 500,000 individual cells. The various molecules that acted as switches enabled the team to identify nearly 200 brain cell types. Even the same gene in the same type of cell could have different characteristics across the brain. One gene was turned on with one switch at the front of the brain and with another at the back. “There are remarkable regional differences,” says study co-author Wei Tian, a computational biologist at the Salk Institute.

Pinpointing the switches that activate or block gene expression in brain cells could be useful for diagnosing brain disorders and developing tailored treatments, says Ecker. “That’s another tool that comes out of the toolbox we’re building,” he says.

Disease risk

Improving understanding of how genetic switches might contribute to disease risk was also a focus for Bing Ren, a molecular biologist at the University of California, San Diego, and his team3. They analysed how more than one million brain cells from the three donors access and use genetic information. The researchers uncovered links between certain brain cell types and neuropsychiatric disorders, including bipolar disorder, depression and schizophrenia.

Ren and his colleagues used the cell-type data to predict how the genetic switches influence gene regulation and increase the risk of neurological diseases. For instance, in cells called microglia , which clear away dead or damaged cells, the presence of some genetic switches was strongly linked to risks of Alzheimer's disease. Such findings can be used to test whether particular genes or faulty switches contribute directly to the onset of disease. “This is made possible because we have — for the first time — delineated the genetic switches for hundreds of different cell types,” says Ren.

The next step for the BICCN team is to sequence more cells from all parts of the brain, says Ren. The researchers will also work with more tissue samples to build a picture of how the human brain can vary across populations and age groups. “This is only the beginning,” says Ren.

doi: https://doi.org/10.1038/d41586-023-03192-2

References

Siletti, K. et al. Science 382, eadd7046 (2023).
Article Google Scholar 
Tian, W. et al. Science 382, eadf5357 (2023).
Article Google Scholar 
Li, Y. E. et al. Science 382, eadf7044 (2023).
Article Google Scholar 

Download referencesReprints and Permissions



本文於 修改第 1 次
回應 回應給此人 推薦文章 列印 加入我的文摘
引用網址:https://city.udn.com/forum/trackback.jsp?no=2976&aid=7216220