Posts tagged brain
Articles and news from the latest research reports.
Neural Pointillism: Lighting Up the Brain in Psychedelic Relief
During the last decade, researchers have labored intensively to find new methods to photograph the complex networks of nerve cells that make up the brain and spinal cord, an attempt to overcome the severe limitations of earlier imaging technologies. The emerging science of connectomics, intended to map such connections, will be made possible by deploying these techniques.
In 2007, Jeff Lichtman, Joshua Sanes and colleagues at Harvard University came up with one of the most notable examples of the new brain-cell imaging methods. Brainbow lights up neurons in about 100 different hues, enabling a precise tracking of neural circuitry and synapses, the gaps between brain cells.
Scientists engineer a mouse or another model animal with a gene that randomly causes each neuron to express differing amounts of a red, green or blue fluorescent protein, producing a palette of varying pastel-like colors. Slices of tissue are photographed and recombined to produce detailed imagery of the brain’s structural topography. (The original discovery of what is called green fluorescent protein by Martin Chalfie, Osamu Shinomura and Roger Y. Tsien, from which these new multi-colored fluorescent proteins are derived, was awarded the 2008 Nobel Prize in Chemistry.)
Brain & Behavior Research Foundation Announces 10 Major Research Achievements of 2012
In 2012, the Brain & Behavior Research Foundation funded more than 200 new promising ideas through its NARSAD Grants to identify the causes, improve treatments and develop prevention strategies for mental illness. Many research projects also came to fruition in 2012, and the Foundation highlights ten significant findings.
Why Do We Blink So Frequently?
We all blink. A lot. The average person blinks some 15-20 times per minute—so frequently that our eyes are closed for roughly 10% of our waking hours overall.
Although some of this blinking has a clear purpose—mostly to lubricate the eyeballs, and occasionally protect them from dust or other debris—scientists say that we blink far more often than necessary for these functions alone. Thus, blinking is physiological riddle. Why do we do it so darn often? In a paper published in the Proceedings of the National Academy of Sciences, a group of scientists from Japan offers up a surprising new answer—that briefly closing our eyes might actually help us to gather our thoughts and focus attention on the world around us.
The researchers came to the hypothesis after noting an interesting fact revealed by previous research on blinking: that the exact moments when we blink aren’t actually random. Although seemingly spontaneous, studies have revealed that people tend to blink at predictable moments. For someone reading, blinking often occurs after each sentence is finished, while for a person listening to a speech, it frequently comes when the speaker pauses between statements. A group of people all watching the same video tend to blink around the same time, too, when action briefly lags.
As a result, the researchers guessed that we might subconsciously use blinks as a sort of mental resting point, to briefly shut off visual stimuli and allow us to focus our attention. To test the idea, they put 10 different volunteers in an fMRI machine and had them watch the TV show “Mr. Bean” (they had used the same show in their previous work on blinking, showing that it came at implicit break points in the video). They then monitored which areas of the brain showed increased or decreased activity when the study participants blinked.
Their analysis showed that when the Bean-watchers blinked, mental activity briefly spiked in areas related to the default network, areas of the brain that operate when the mind is in a state of wakeful rest, rather than focusing on the outside world. Momentary activation of this alternate network, they theorize, could serve as a mental break, allowing for increased attention capacity when the eyes are opened again.
To test whether this mental break was simply a result of the participants’ visual inputs being blocked, rather than a subconscious effort to clear their minds, the researchers also manually inserted “blackouts” into the video at random intervals that lasted roughly as long as a blink. In the fMRI data, though, the brain areas related to the default network weren’t similarly activated. Blinking is something more than temporarily not seeing anything.
It’s far from conclusive, but the research demonstrates that we do enter some sort of altered mental state when we blink—we’re not just doing it to lubricate our eyes. A blink could provide a momentary island of introspective calm in the ocean of visual stimuli that defines our lives.
Brain displays an intrinsic mechanism for fighting infection
White blood cells have long reigned as the heroes of the immune system. When an infection strikes, the cells, produced in bone marrow, race through the blood to fight off the pathogen. But new research is emerging that individual organs can also play a role in immune system defense, essentially being their own hero. In a study examining a rare and deadly brain infection, scientists at The Rockefeller University have found that the brain cells of healthy people likely produce their own immune system molecules, demonstrating an “intrinsic immunity” that is crucial for stopping an infection.
Shen-Ying Zhang, a clinical scholar in the St. Giles Laboratory of Human Genetics of Infectious Diseases, has been studying children with Herpes simplex encephalitis, a life-threatening brain infection from the herpes virus, HSV-1, that can cause significant brain damage. The scientists already knew from previous work that children with this encephalitis have a genetic defect that impairs the function of an immune system receptor — toll-like receptor 3 (TLR3) — in the brain. For this study they wanted to see how the defect in TLR3 was hampering the brain’s ability to fight the herpes infection.
When TLR3 detects a pathogen it triggers an immune response causing the release of proteins called interferons to sound the alarm and “interfere” with the pathogen’s replication. It’s most commonly associated with white blood cells, found throughout the body, but here the researchers were examining the receptor’s presence on neurons and other brain cells.
“One interesting thing about these patients is that they didn’t have any of the other, more common herpes symptoms. They didn’t have an infection on their skin or their mouths, just in their brains. We therefore hypothesized that the TLR3 response must be specifically responsible for keeping the herpes virus from infecting the brain and not necessary in other parts of the body,” says Zhang.
The lab, headed by Jean-Laurent Casanova, collaborated with scientists at Harvard Medical School and Memorial Sloan-Kettering Cancer Institute to create induced pluripotent stem cells. Made from the patients’ own tissue, the stem cells were developed into central nervous system cells that carried the patients’ genetic defects. Zhang exposed the cells to HSV-1 and to synthetic double-stranded RNA, which mimics a byproduct of the virus that spurs the toll-like receptors into action. By measuring levels of interferon, Zhang showed that the patients’ TLR3 response was indeed faulty; their cells weren’t making these important immune system proteins, leaving them unable to fight off the infection.
Zhang also exposed the patients’ blood cells to the virus and found that the TLR3 defect was not an issue there as it was in the brain — interferons were released by other means.
Because the toll-like receptors on neurons proved to be vital in preventing the encephalitis infection, the researchers concluded that brain cells use it as an in-house mechanism to fight infection, rather than relying on white blood cells. When its function was impaired, patients couldn’t get better.
“This is evidence of an intrinsic immunity, a newly-discovered function of the immune system,” says Zhang. “It’s likely that other organs also have their own specific tools for fighting infection.”
The researchers are putting together a pilot study to test an interferon-based treatment in patients with the encephalitis, believing it will help speed recovery and increase the survival rate when used alongside antiviral drugs. They’ll also explore whether the brain displays an intrinsic immunity to other types of viral infection.
Why overlearned sequences are special: distinct neural networks for ordinal sequences
Several observations suggest that overlearned ordinal categories (e.g., letters, numbers, weekdays, months) are processed differently than non-ordinal categories in the brain. In synesthesia, for example, anomalous perceptual experiences are most often triggered by members of ordinal categories (Rich et al., 2005; Eagleman, 2009). In semantic dementia (SD), the processing of ordinal stimuli appears to be preserved relative to non-ordinal ones (Cappelletti et al., 2001). Moreover, ordinal stimuli often map onto unconscious spatial representations, as observed in the SNARC effect (Dehaene et al., 1993; Fias, 1996). At present, little is known about the neural representation of ordinal categories. Using functional neuroimaging, we show that words in ordinal categories are processed in a fronto-temporo-parietal network biased toward the right hemisphere. This differs from words in non-ordinal categories (such as names of furniture, animals, cars, and fruit), which show an expected bias toward the left hemisphere. Further, we find that increased predictability of stimulus order correlates with smaller regions of BOLD activation, a phenomenon we term prediction suppression. Our results provide new insights into the processing of ordinal stimuli, and suggest a new anatomical framework for understanding the patterns seen in synesthesia, unconscious spatial representation, and SD.
Decision to give a group effort in the brain
A monkey would probably never agree that it is better to give than to receive, but they do apparently get some reward from giving to another monkey.
During a task in which rhesus macaques had control over whether they or another monkey would receive a squirt of fruit juice, three distinct areas of the brain were found to be involved in weighing benefits to oneself against benefits to the other, according to new research by Duke University researchers.
The team used sensitive electrodes to detect the activity of individual neurons as the animals weighed different scenarios, such as whether to reward themselves, the other monkey or nobody at all. Three areas of the brain were seen to weigh the problem differently depending on the social context of the reward. The research appears Dec. 24 in the journal Nature Neuroscience.
Using a computer screen to allocate juice rewards, the monkeys preferred to reward themselves first and foremost. But they also chose to reward the other monkey when it was either that or nothing for either of them. They also were more likely to give the reward to a monkey they knew over one they didn’t, preferred to give to lower status than higher status monkeys, and had almost no interest in giving the juice to an inanimate object.
Calculating the social aspects of the reward system seems to be a combination of action by two centers involved in calculating all sorts of rewards and a third center that adds the social dimension, according to lead researcher Michael Platt, director of the Duke Institute for Brain Sciences and the Center for Cognitive Neuroscience.
The orbital frontal cortex, right above the eyes, was activated when calculating rewards to the self. The anterior cingulate sulcus in the middle of the top of the brain seemed to calculate giving up a reward. But both centers appear “divorced from social context,” Platt said. A third area, the anterior cingulate gyrus (ACCg), seemed to “care a lot about what happened to the other monkey,” Platt said.
Based on results of various combinations of the reward-giving scenario the monkeys were put through, it would appear that neurons in the ACCg encode both the giving and receiving of rewards, and do so in a remarkably similar way.
The use of single-neuron electrodes to measure the activity of brain areas gives a much more precise picture than brain imaging, Platt said. Even the best imaging available now is “a six-second snapshot of tens of thousands of neurons,” which are typically operating in milliseconds.
What the team has seen happening is consistent with other studies of damaged ACCg regions in which animals lost their typical hesitation about retrieving food when facing social choices. This same region of the brain is active in people when they empathize with someone else.
"Many neurons in the anterior cingulate gyrus (ACCg) respond both when monkeys choose a drink for themselves and when they choose to give a drink to another monkey," Platt said. "One might view these as sort of mirror neurons for the reward system." The region is active as an animal merely watches another animal receiving a reward without having one themselves.
The research is another piece of the puzzle as neuroscientists search for the roots of charity and social behavior in our species and others. There have been two schools of thought about how the social reward system is set up, Platt said. One holds that there is generic circuitry for rewards that has been adapted to our social behavior because it helped humans and other social animals like monkeys thrive. Another school holds that social behavior is so important to humans and other highly social animals like monkeys that there may be some special circuits for it, Platt said.
This finding, in macaques that have only a very distant common ancestor with us and are “not a particularly prosocial animal,” suggests that “this specialized social circuitry evolved a long time ago presumably to support cooperative behavior,” Platt said.
(Photo: EPA)
The Top 5 Neuroscience Breakthroughs of 2012
More than any year before, 2012 was the year neuroscience exploded into pop culture. From mind-controlled robot hands to cyborg animals to TV specials to triumphant books, brain breakthroughs were tearing up the airwaves and the internets. From all the thrilling neurological adventures we covered over the past year, we’ve collected five stories we want to make absolutely sure you didn’t miss.
A Roadmap of Brain Wiring
Neuroscientists like to compare the task of unraveling the brain’s connections to the frustration of untangling the cords beneath your computer desk – except that in the brain, there are hundreds of millions of cords, and at least one hundred trillion plugs. Even with our most advanced computers, some researchers were despairing of ever seeing a complete connectivity map of the human brain in our lifetimes. But thanks to a team led by Van Wedeen at the Martinos Center for Biomedical Imaging at Massachusetts General Hospital, 2012 gave us an unexpectedly clear glimpse of our brains’ large-scale wiring patterns. As it turns out, the overall pattern isn’t so much a tangle as a fabric – an intricate, multi-layered grid of cross-hatched neural highways. What’s more, it looks like our brains share this grid pattern with many other species. We’re still a long way from decoding how most of this wiring functions, but this is a big step in the right direction.
Laser-Controlled Desire
Scientists have been stimulating rats’ pleasure centers since the 1950s – but 2012 saw the widespread adoption of a new brain-stimulation method that makes all those wires and incisions look positively crude. Researchers in the blossoming field of optogenetics develop delicate devices that control the firing of targeted groups of neurons – using only light itself. By hooking rats up to a tiny fiber-optic cable and firing lasers directly into their brains, a team led by Garret D. Stuber at the University of North Carolina at Chapel Hill School of Medicine were able to isolate specific neurochemical shifts that cause rats to feel pleasure or anxiety – and switch between them at will. This method isn’t only more precise than electrical stimulation – it’s also much less damaging to the animals.
Programmable Brain Cells
Pluripotent stem cell research took off like a rocket in 2012. After discovering that skin cells can be genetically reprogrammed into stem cells, which can in turn be reprogrammed into just about any cell in the human body, a team led by Sheng Ding at UCSF managed to engineer a working network of newborn neurons from a harvest of old skin cells. In other words, the team didn’t just convert skin cells into stem cells, then into neurons – they actually kept the batch of neurons alive and functional long enough to self-organize into a primitive neural network. In the near future, it’s likely that we’ll be treating many kinds of brain injuries by growing brand-new neurons from other kinds of cells in a patient’s own body. This is already close on the horizon for liver and heart cells – but the thought of being able to technologically shape the re-growth of a damaged brain is even more exciting.
Memories on Disc
We’ve talked a lot about how easily our brains can modify and rewrite our long-term memories of facts and scenarios. In 2012, though, researchers went Full Mad Scientist with the implications of this knowledge, and blew some mouse minds in the process. One team, led by Mark Mayford of the Scripps Research Institute, took advantage of some recently invented technology that enables scientists to record and store a mouse’s memory of a familiar place on a microchip. Mayford’s team figured out how to turn specific mouse memories on and off with the flick of a switch – but they were just getting warmed up. The researchers then proceeded to record a memory in one mouse’s brain, transfer it into another mouse’s nervous system, and activate it in conjunction with one of the second mouse’s own memories. The result was a bizarre “hybrid memory” – familiarity with a place the mouse had never visited. Well, not in the flesh, anyway.
Videos of Thoughts
Our most exciting neuroscience discovery of 2012 is also one of the most controversial. A team of researchers from the Gallant lab at UC Berkeley discovered a way to reconstruct videos of entire scenes from neural activity in a person’s visual cortex. Those on the cautionary side emphasize that activity in the visual cortex is fairly easy to decode (relatively speaking, of course) and that we’re still a long, long way from decoding videos of imaginary voyages or emotional palettes. In fact, from one perspective, this isn’t much different from converting one file format into another. On the other hand, though, these videos offer the first hints of the technological reality our children may inhabit: A world where the boundaries between the objective external world and our individual subjective experiences are gradually blurred and broken down. When it comes to transforming our relationship with our own consciousness – and those of the people around us – it doesn’t get much more profound than that.
Carbon nanotubes could one day enhance your brain
Swiss Federal Institute of Technology scientists found that carbon nanotubes offer the potential to establish functional links between neurons that could fight disease and enhance our brains.
The human brain contains about 10 billion neurons, each connecting to other nerve cells through 10,000 or more synapses. Neurons process signals from these connections, then produce output commands that stimulate biological functions, everything from breathing to thinking to kissing.
Many scientists consider our brain similar to a massive parallel processing system, a supercomputer. However, when that computer breaks down we can lose memory or worse, develop sicknesses such as Parkinson’s, Alzheimer’s or other forms of dementia.
Unfortunately, we can’t take our brain down to Wall Mart or Fry’s for an upgrade; however, what if we could put something in our brain that would enhance the signal processing capabilities of individual neurons. Swiss scientists say they’ve done just that with carbon nanotubes.
The forward-thinking research team; led by Michel Giugliano, now a professor at the University of Antwerp, created carbon nanotube scaffolds, which serve as electrical bypass circuitry, to not only repair faulty neural networks, but also enhance performance of healthy cells.
Although there are still some engineering hurdles to overcome, the scientists see huge potential for strengthening neural networks with carbon nanotubes. This procedure could allow brain-machine interfaces for neuroprosthetics that process sight, sound, smell and motion.
Such circuits might be used, for instance, to veto epileptic attacks before they occur, perform spinal bypasses around injuries, and repair or enhance normal cognitive functions. In the not-too-distant future, non-biological nano-neurons could enable our brains to process information much faster than today’s biological brains can.
MRI Could Solve Cellphone Radiation Problems
Years of studies to determine whether cellphones can cause brain tumors have yielded one popular consensus: More studies are needed. One important piece that has been missing from researchers’ arsenals is a way to see what happens to cellphone radiation that is absorbed by the human brain. Two scientists have now developed a magnetic resonance imaging (MRI) technique that they say could solve that problem. This could be an important tool for researchers who are trying to discover whether extensive cellphone use can cause brain tumors or other health problems.
The technique creates high-resolution 3-D images of the heat created by cellphone radiation absorbed in the brain. In research reported this week in Proceedings of the National Academy of Sciences, the scientists demonstrate the method on cow brain matter and a gel that emulates brain tissue. But the procedure could easily be adapted for tests on human brains, says David Gultekin, a medical physicist at Memorial Sloan-Kettering Cancer Center, in New York, who led the development of the technique.
Simple Innovation to Electrodes Makes a Big Difference
The electroencephalogram (EEG) for human uses has been around since 1924. Small metal discs placed along the scalp measure electrical activity in the human brain, important in diagnosing or evaluating epilepsy, sleep disorders and other conditions.
But these electrodes have changed little since their introduction, and are far from perfect. Among other things, they pick up extraneous noise and movement in addition to brain wave activity, often making the readings difficult to interpret.
Walt Besio thinks he has a better way.
The National Science Foundation-funded scientist, who is associate professor of biomedical engineering at the University of Rhode Island, has invented a new and improved electrode, one that produces a performance difference that he says is akin to “taking the rabbit ears you used to have for your television set, and converting to high definition.”
His innovation is relatively simple, but apparently makes a big difference. Besio added two new metal rings around the basic disc, a change that eliminates outside noises and improves spatial resolution.
"EEG has two main problems: It’s very noisy and contaminated with artifacts, and it’s spatial resolution is bad," he explains. "We have improved the signal-to-noise ratio. It’s four times better than it was before. Because it is now a very local signal, it means we can put electrodes closer together, which improves spatial resolution, meaning you can better determine where the signal is coming from."
The additional rings work almost like an inner tube tossed on top of a rippling body of water. “The water is flat in the center of the inner tube and choppy on the outside,” he says. “The outer rings on the electrodes behave like that inner tube.”
For researchers and clinicians, having improved electrodes could open up potential new uses, as well as improve current ones-more accurate epilepsy diagnosis, for example, as well as the promise of “reading” someone’s thoughts in the future, with the goal, for example, of activating an otherwise inert body part, such as an arm or leg, and ultimately helping people with spinal cord injuries.
The aim is to have the highly sensitive electrodes first translate a person’s thoughts into electrical impulses that can be read by a computer, then, eventually move to robots, and later, limbs. Other scientists are conducting similar research, but Besio wants to show “that it works better with these types of electrodes.”