Posts Tagged ‘research’

By Emily Underwood

One of the thorniest debates in neuroscience is whether people can make new neurons after their brains stop developing in adolescence—a process known as neurogenesis. Now, a new study finds that even people long past middle age can make fresh brain cells, and that past studies that failed to spot these newcomers may have used flawed methods.

The work “provides clear, definitive evidence that neurogenesis persists throughout life,” says Paul Frankland, a neuroscientist at the Hospital for Sick Children in Toronto, Canada. “For me, this puts the issue to bed.”

Researchers have long hoped that neurogenesis could help treat brain disorders like depression and Alzheimer’s disease. But last year, a study in Nature reported that the process peters out by adolescence, contradicting previous work that had found newborn neurons in older people using a variety of methods. The finding was deflating for neuroscientists like Frankland, who studies adult neurogenesis in the rodent hippocampus, a brain region involved in learning and memory. It “raised questions about the relevance of our work,” he says.

But there may have been problems with some of this earlier research. Last year’s Nature study, for example, looked for new neurons in 59 samples of human brain tissue, some of which came from brain banks where samples are often immersed in the fixative paraformaldehyde for months or even years. Over time, paraformaldehyde forms bonds between the components that make up neurons, turning the cells into a gel, says neuroscientist María Llorens-Martín of the Severo Ochoa Molecular Biology Center in Madrid. This makes it difficult for fluorescent antibodies to bind to the doublecortin (DCX) protein, which many scientists consider the “gold standard” marker of immature neurons, she says.

The number of cells that test positive for DCX in brain tissue declines sharply after just 48 hours in a paraformaldehyde bath, Llorens-Martín and her colleagues report today in Nature Medicine. After 6 months, detecting new neurons “is almost impossible,” she says.

When the researchers used a shorter fixation time—24 hours—to preserve donated brain tissue from 13 deceased adults, ranging in age from 43 to 87, they found tens of thousands of DCX-positive cells in the dentate gyrus, a curled sliver of tissue within the hippocampus that encodes memories of events. Under a microscope, the neurons had hallmarks of youth, Llorens-Martín says: smooth and plump, with simple, undeveloped branches.

In the sample from the youngest donor, who died at 43, the team found roughly 42,000 immature neurons per square millimeter of brain tissue. From the youngest to oldest donors, the number of apparent new neurons decreased by 30%—a trend that fits with previous studies in humans showing that adult neurogenesis declines with age. The team also showed that people with Alzheimer’s disease had 30% fewer immature neurons than healthy donors of the same age, and the more advanced the dementia, the fewer such cells.

Some scientists remain skeptical, including the authors of last year’s Nature paper. “While this study contains valuable data, we did not find the evidence for ongoing production of new neurons in the adult human hippocampus convincing,” says Shawn Sorrells, a neuroscientist at the University of Pittsburgh in Pennsylvania who co-authored the 2018 paper. One critique hinges on the DCX stain, which Sorrells says isn’t an adequate measure of young neurons because the DCX protein is also expressed in mature cells. That suggests the “new” neurons the team found were actually present since childhood, he says. The new study also found no evidence of pools of stem cells that could supply fresh neurons, he notes. What’s more, Sorrells says two of the brain samples he and his colleagues looked at were only fixed for 5 hours, yet they still couldn’t find evidence of young neurons in the hippocampus.

Llorens-Martín says her team used multiple other proteins associated with neuronal development to confirm that the DCX-positive cells were actually young, and were “very strict,” in their criteria for identifying young neurons.

Heather Cameron, a neuroscientist at the National Institute of Mental Health in Bethesda, Maryland, remains persuaded by the new work. Based on the “beauty of the data” in the new study, “I think we can all move forward pretty confidently in the knowledge that what we see in animals will be applicable in humans, she says. “Will this settle the debate? I’m not sure. Should it? Yes.”

https://www.sciencemag.org/news/2019/03/new-neurons-life-old-people-can-still-make-fresh-brain-cells-study-finds?utm_campaign=news_daily_2019-03-25&et_rid=17036503&et_cid=2734364

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by David Nield

How exactly do our brains sort between the five taste groups: sweet, sour, salty, bitter and umami? We’ve now got a much better idea, thanks to research that has pinned down where in the brain this taste processing happens.

Step forward: the insular cortex. Already thought to be responsible for everything from motor control to social empathy, we can now add flavour identification to its list of jobs.

It’s an area of the brain scientists have previously suspected could be responsible for sorting tastes, and which has been linked to taste in rodents, but this new study is much more precise in figuring out the role it plays in decoding what our tongues are telling us.

“We have known that tastes activate the human brain for some time, but not where primary taste types such as sweet, sour, salty, and bitter are distinguished,” says one of the team, Adam Anderson from Cornell University in New York.

“By using some new techniques that analyse fine-grained activity patterns, we found a specific portion of the insular cortex – an older cortex in the brain hidden behind the neocortex – represents distinct tastes.”

Anderson and his team used detailed fMRI scans of 20 adults as well as a new statistical model to dig deeper than previous studies into the link between the insular cortex and taste. This helped separate the taste response from other related responses – like the disgust we might feel when eating something sour or bitter.

Part of the problem in pinning down the taste-testing parts of the brain is that multiple regions of neurons get busy whenever we’re eating something. However, this study helps to cut through some of that noise.

In particular, it seems that different tastes don’t necessarily affect different parts of the insular cortex, but rather prompt different patterns of activity. Those patterns help the brain determine what it’s tasting.

For example, one particular section of the insular cortex was found to light up – in terms of neural activity – whenever something sweet was tasted. It’s a literal sweet spot, in other words, but it also showed that different brains have different wiring.

“While we identified a potential sweet spot, its precise location differed across people and this same spot responded to other tastes, but with distinct patterns of activity,” says Anderson.

“To know what people are tasting, we have to take into account not only where in the insula is stimulated, but also how.”

The work follows on from previous research showing just how big a role the brain plays in perceiving taste. It used to be thought that receptors on the tongue did most of the taste testing, but now it seems the brain is largely in charge of the process.

That prior study showed how switching certain brain cells on and off in mice was enough to prevent them from distinguishing between sweet and bitter. The conclusion is that while the tongue does identify certain chemicals, it’s the brain that interprets them.

The new research adds even more insight into what’s going on in the brain in humans when we need to work out what we’re tasting – and shows just how important a job the insular cortex is doing.

“The insular cortex represents experiences from inside our bodies,” says Anderson. “So taste is a bit like perceiving our own bodies, which is very different from other external senses such as sight, touch, hearing or smell.”

The research has been published in Nature Communications.

https://www.sciencealert.com/now-we-know-the-part-of-the-brain-that-tells-us-what-we-re-tasting

by CARLY CASSELLA

Scientists are closing in on a blood test for fibromyalgia, and the result could save patients from what is currently a lengthy and vague process of diagnosis.

Researchers at Ohio State University are now aiming to have a diagnostic blood test available for widespread use within the next five years.

Their confidence stems from a recently discovered biomarker – a “metabolic fingerprint” as the researchers put it – traceable in the blood of those with the disorder.

“We found clear, reproducible metabolic patterns in the blood of dozens of patients with fibromyalgia,” says lead author Kevin Hackshaw, a rheumatologist at Ohio State University.

“This brings us much closer to a blood test than we have ever been.”

Fibromyalgia is a common, debilitating, and poorly understood disorder, marked by widespread pain and fatigue, with no known cause and absolutely no cure.

In the United States, it’s the most common cause of chronic widespread pain, and that’s not even counting the thousands of patients who go undiagnosed every year.

Without a reliable way to detect this disorder, it’s estimated that up to three out of four people with the condition remain undiagnosed. And on average it can take five years from when a person’s symptoms first appear to them actually receiving a diagnosis.

In total, the US Centers for Disease Control and Prevention estimates that about two percent of the population – around four million adults – have fibromyalgia, with women making up a disproportionate slice.

Left with few options, many patients are simply forced to live with their pain.With nowhere to go, many become desperate and turn to potentially harmful treatments.

“When you look at chronic pain clinics, about 40 percent of patients on opioids meet the diagnostic criteria for fibromyalgia,” says Hackshaw.

“Fibromyalgia often gets worse, and certainly doesn’t get better, with opioids.”

It was Hackshaw’s goal to intervene sooner. Using vibrational spectroscopy, a technique which measures the energy of molecules, his team analysed blood samples from 50 people with fibromyalgia, 29 with rheumatoid arthritis, 19 with osteoarthritis, and 23 with lupus.

Despite the fact these disorders can present with similar symptoms, the blood of those participants with fibromyalgia was distinct.

Using these unique patterns, the researchers then tried to blindly predict participants’ diagnoses. Even without knowing their true disorder, the researchers were able to accurately diagnose every study participant based on that molecular fingerprint in the blood.

“These initial results are remarkable,” says co-author Luis Rodriguez-Saona, an expert in vibrational spectroscopy at Ohio State University.

“If we can help speed diagnosis for these patients, their treatment will be better and they’ll likely have better outlooks. There’s nothing worse than being in a grey area where you don’t know what disease you have.”

While the sample size is undoubtedly small, the results are promising. If the team can replicate their results on a larger scale, with a couple hundred diverse participants, then a blood test in five years might not seem so far-fetched.

Not to mention what that would mean for treatment. If the researchers can prove they really have identified a biological fingerprint for fibromyalgia, this could give us new drug targets in the future.

“Thus,” the authors conclude, “our studies have great importance both from development of a reproducible biomarker as well as identifying potential new therapeutic targets for treatment.”

This study has been published in the Journal of Biological Chemistry.

https://www.sciencealert.com/scientists-have-devised-a-blood-test-that-can-accurately-diagnose-fibromyalgia

Neuroscientists can read brain activity to predict decisions 11 seconds before people actFree will, from a neuroscience perspective, can look like quite quaint. In a study published this week in the journal Scientific Reports, researchers in Australia were able to predict basic choices participants made 11 seconds before they consciously declared their decisions.

In the study, 14 participants—each placed in an fMRI machine—were shown two patterns, one of red horizontal stripes and one of green vertical stripes. They were given a maximum of 20 seconds to choose between them. Once they’d made a decision, they pressed a button and had 10 seconds to visualize the pattern as hard as they could. Finally, they were asked “what did you imagine?” and “how vivid was it?” They answered these questions by pressing buttons.

Using the fMRI to monitor brain activity and machine learning to analyze the neuroimages, the researchers were able to predict which pattern participants would choose up to 11 seconds before they consciously made the decision. And they were able to predict how vividly the participants would be able to envisage it.

Lead author Joel Pearson, cognitive neuroscience professor at the University of South Wales in Australia, said that the study suggests traces of thoughts exist unconsciously before they become conscious. “We believe that when we are faced with the choice between two or more options of what to think about, non-conscious traces of the thoughts are there already, a bit like unconscious hallucinations,” he said in a statement. “As the decision of what to think about is made, executive areas of the brain choose the thought-trace which is stronger. In, other words, if any pre-existing brain activity matches one of your choices, then your brain will be more likely to pick that option as it gets boosted by the pre-existing brain activity.”

The work has implications for how we understand uncomfortable thoughts: Pearson believes the findings explain why thinking about something only leads to more thoughts on the subject, as it creates “a positive feedback loop.” The study also suggests that unwelcome visualizations, such as those experienced with post-traumatic stress disorder, begin as unconscious thoughts.

Though this is just one study, it’s not the first to show that thoughts can be predicted before they are conscious. As the researchers note, similar techniques have been able to predict motor decisions between seven and 10 seconds before they’re conscious, and abstract decisions up to four seconds before they’re conscious. Taken together, these studies show how understanding how the brain complicates our conception of free will.

Neuroscientists have long known that the brain prepares to act before you’re consciously aware, and there are just a few milliseconds between when a thought is conscious and when you enact it. Those milliseconds give us a chance to consciously reject unconscious impulses, seeming to form a foundation of free will.

Freedom, however, can be enacted by both the unconscious and conscious self—and there are neuroscientists who claim that being controlled by our own unconscious brain is hardly an affront to free will. Studies showing that neuroscientists can predict our actions long before we’re aware of them don’t necessarily negate the concept of free will, but they certainly complicate our conception of our own minds.

https://qz.com/1569158/neuroscientists-read-unconscious-brain-activity-to-predict-decisions/?utm_source=google-news

By David Freeman

No one is ditching the night-vision goggles just yet, but scientists working in the United States and China have developed a technique that they say could one day give humans the ability to see in the dark.

The technique involves injecting the eyes with particles that act like tiny antennae that take infrared light — wavelengths that are invisible to humans and other mammals — and convert it to visible wavelengths. Mammals can see wavelengths in just a sliver of the electromagnetic spectrum, and the new technique is designed to widen that sliver.

The nanoparticle injections haven’t been tried on humans, but experiments on mice show that they confer the ability to see infrared light without interfering with the perception of light in the visible range. The effect worked during the day and at night and lasted for several weeks. The rodents were left unharmed once it wore off.

Gang Han, a chemist at the University of Massachusetts Medical School and a co-author of a new paper describing the research, said in a statement that the technique could lead to a better understanding of visual perception and possibly lead to new ways to treat color blindness.

But those are far from the only possible applications if the technique can be made to work safely in other mammals, including humans. In an email to NBC News MACH, Han said it might be possible to use nanoparticle injections to create “superdogs” that could make it easier to apprehend lawbreakers in darkness.

“For ordinary people,” he added, “we may also see our sky in a completely different way” both at night and during the day because many celestial objects give off infrared light.

The technique doesn’t confer the ability to see the longer-wavelength infrared light given off by living bodies and other warm objects, Tian Xue, a neuroscientist at the University of Science and Technology of China and a co-author of the paper, said in an email. But at least theoretically, it could give humans the ability to see bodies and objects in darkness without the use of night-vision gear — though an infrared light would still be needed.

For their research, Han, Xue and their collaborators injected the rodents’ eyes with nanoparticles treated with proteins that helped “glue” the particles to light-sensitive cells in the animals’ retinas. Once the tiny antennae were in place, the scientists hypothesized, the nanoparticles would convert infrared light into shorter wavelengths, which the animals would then perceive as green light.

To make sure the mice were actually seeing the converted infrared light, the scientists subjected the animals to a number of tests, including one in which they were given a choice of entering a totally dark box or one illuminated only with infrared light. (Mice are nocturnal, and ordinarily they prefer darkness.) Control animals showed no preference — because both boxes appeared dark to them — while treated mice showed a distinct preference for the dark box.

Other scientists praised the research while expressing doubts about trying the technique in humans.

Harvard neuroscientist Michael Do said in an email that the experiments were “sophisticated” and that the technique was likely to work in humans as well as in mice. But he said it was unclear just how sharp the infrared vision would be in humans, and he cautioned that the injections might damage delicate structures in the eye.

Glen Jeffery, a neuroscientist at the University College London, expressed similar praise for the research — but even graver doubts. “Injecting any material under the retina is risky and should never be done unless there is a clear and justifiable clinical reason…” he said in an email. “I have no idea how you could use this technology to human advantage and would never support its application on healthy humans.”

But the researchers are moving ahead. Han said the team planned to test the technique in bigger animals — possibly dogs.

https://www.nbcnews.com/mach/science/scientists-create-super-mice-can-see-dark-here-s-what-ncna977966

Thanks to Kebmodee for bringing this to the It’s Interesting community.

by PETER DOCKRILL

Scientists think they’ve identified a previously unknown form of neural communication that self-propagates across brain tissue, and can leap wirelessly from neurons in one section of brain tissue to another – even if they’ve been surgically severed.

The discovery offers some radical new insights about the way neurons might be talking to one another, via a mysterious process unrelated to conventionally understood mechanisms, such as synaptic transmission, axonal transport, and gap junction connections.

“We don’t know yet the ‘So what?’ part of this discovery entirely,” says neural and biomedical engineer Dominique Durand from Case Western Reserve University.

“But we do know that this seems to be an entirely new form of communication in the brain, so we are very excited about this.”

Before this, scientists already knew there was more to neural communication than the above-mentioned connections that have been studied in detail, such as synaptic transmission.

For example, researchers have been aware for decades that the brain exhibits slow waves of neural oscillations whose purpose we don’t understand, but which appear in the cortex and hippocampus when we sleep, and so are hypothesised to play a part in memory consolidation.

“The functional relevance of this input‐ and output‐decoupled slow network rhythm remains a mystery,” explains neuroscientist Clayton Dickinson from the University of Alberta, who wasn’t involved in the new research but has discussed it in a perspective article.

“But [it’s] one that will probably be solved by an elucidation of both the cellular and the inter‐cellular mechanisms giving rise to it in the first place.”

To that end, Durand and his team investigated slow periodic activity in vitro, studying the brain waves in hippocampal slices extracted from decapitated mice.

What they found was that slow periodic activity can generate electric fields which in turn activate neighbouring cells, constituting a form of neural communication without chemical synaptic transmission or gap junctions.

“We’ve known about these waves for a long time, but no one knows their exact function and no one believed they could spontaneously propagate,” Durand says.

“I’ve been studying the hippocampus, itself just one small part of the brain, for 40 years and it keeps surprising me.”

This neural activity can actually be modulated – strengthened or blocked – by applying weak electrical fields and could be an analogue form of another cell communication method, called ephaptic coupling.

The team’s most radical finding was that these electrical fields can activate neurons through a complete gap in severed brain tissue, when the two pieces remain in close physical proximity.

“To ensure that the slice was completely cut, the two pieces of tissue were separated and then rejoined while a clear gap was observed under the surgical microscope,” the authors explain in their paper.

“The slow hippocampal periodic activity could indeed generate an event on the other side of a complete cut through the whole slice.”

If you think that sounds freaky, you’re not the only one. The review committee at The Journal of Physiology – in which the research has been published – insisted the experiments be completed again before agreeing to print the study.

Durand et al. dutifully complied, but sound pretty understanding of the cautiousness, all things considered, given the unprecedented weirdness of the observation they’re reporting.

“It was a jaw-dropping moment,” Durand says, “for us and for every scientist we told about this so far.”

“But every experiment we’ve done since to test it has confirmed it so far.”

It’ll take a lot more research to figure out if this bizarre form of neural communication is taking place in human brains – let alone decoding what exact function it performs – but for now, we’ve got new science that’s shocking in all kinds of ways, as Dickson adroitly observes.

“While it remains to be seen if the [findings] are relevant to spontaneous slow rhythms that occur in both cortical and hippocampal tissue in situ during sleep and sleep‐like states,” Dickson writes, “they should probably (and quite literally) electrify the field.”

The findings are reported in The Journal of Physiology.

https://www.sciencealert.com/neuroscientists-say-they-ve-found-an-entirely-new-form-of-neural-communication

by Ruth Williams

The brains of people in vegetative, partially conscious, or fully conscious states have differing profiles of activity as revealed by functional magnetic resonance imaging (fMRI), according to a report today (February 6) in Science Advances. The results of the study indicate that, compared with patients lacking consciousness, the brains of healthy individuals exhibit highly dynamic and complex connectivity.

“This new study provides a substantial advance in characterizing the ‘fingerprints’ of consciousness in the brain” Anil Seth, a neuroscientist at the University of Sussex, UK, who was not involved in the project, writes in an email to The Scientist. “It opens new doors to determining conscious states—or their absence—in a range of different conditions.”

A person can lose consciousness temporarily, such as during sleep or anesthesia, or more permanently as is the case with certain brain injuries. But while unconsciousness manifests behaviorally as a failure to respond to stimuli, such behavior is not necessarily the result of unconsciousness.

Some seemingly unresponsive patients, for example, can display brain activities similar to those of fully conscious individuals when asked to imagine performing a physical task such as playing tennis. Such a mental response in the absence of physical feedback is a condition known as cognitive-motor dissociation.

Researchers are therefore attempting to build a better picture of what is happening in the human brain during consciousness and unconsciousness. In some studies, electroencephalography (EEG) recordings of the brain’s electrical activities during sleep, under anesthesia, or after brain injury have revealed patterns of brain waves associated with consciousness. But, says Jacobo Sitt of the Institute of Brain and Spinal Cord in Paris, such measurements do not provide good spatial information about brain activity. With fMRI, on the other hand, “we know where the activity is coming from.”

Sitt and colleagues performed fMRI brain scans on a total of 47 healthy individuals and 78 patients who either had unresponsive wakefulness syndrome (UWS)—a vegetative state in which the patient’s eyes open, but they never exhibit voluntary movement—or were in a minimally conscious state (MCS)—having more complex behaviors, such as the ability to follow an object with their eyes, but remaining unable to communicate thoughts or feelings. The scans were performed by an international team of collaborators at three different facilities in Paris, New York, and Liège, Belgium.

Data from the fMRI scans, which generated roughly 400 images in approximately 20 minutes for each patient, was computationally analyzed for identifiable patterns of activity. Four patterns were reproducibly detected within the data from each facility. And, for two of these patterns, the likelihood of their occurrence in a given individual’s scan depended on diagnosis.

Healthy individuals, for example, were more likely than patients to display pattern 1—characterized by high spatial complexity and interregional connectivity indicating brain-wide coordination. Patients with UWS, on the other hand, rarely displayed pattern 1, most often displaying pattern 4—characterized by low complexity and reduced interregional connectivity. Generally speaking, MCS patients fell somewhere between. The occurrence of patterns 2 and 3 were equally likely across all groups.

The team went on to analyze a second set of 11 patients at a facility in Ontario, Canada. Again the four distinct patterns were detected within the fMRI images. Six of these patients had UWS and predominantly displayed pattern 4, while the remaining five, who had cognitive-motor dissociation, had higher rates of pattern 1, supporting previous evidence for consciousness in these patients.

With such a mix of patients, facilities, scanners, and researchers, the study “had every possibility of failing,” says neuroscientist Tristan Bekinschtein of the University of Cambridge, UK, who did not participate in the research. However, the results were “brutally consistent,” he says.

Having identifiable signatures of consciousness and unconsciousness might ultimately help doctors and families make difficult decisions about continuing life support for vegetative patients, says anesthesiology researcher Anthony Hudetz of the University of Michigan who was not involved with the work. It might also provide insight into whether particular rehabilitation methods or other treatments are working.

“All that hinges on a better understanding of what goes on in the brains of these patients versus healthy or aware [people],” Hudetz says. To that end, this paper “makes a major step forward.”

A. Demertzi et al., “Human consciousness is supported by dynamic complex patterns of brain signal coordination,” Sci Adv, 5: eaat7603, 2019.

https://www.the-scientist.com/news-opinion/neural-patterns-of-consciousness-identified-65433