Space travel may be harmful to the brain, study suggests; Prolonged cosmic radiation exposure could hasten Alzheimer's

Dec. 31, 2012 — As if space travel was not already filled with enough dangers, a new study out today in the journal PLOS ONE shows that cosmic radiation -- which would bombard astronauts on deep space missions to places like Mars -- could accelerate the onset of Alzheimer's disease.

"Galactic cosmic radiation poses a significant threat to future astronauts," said M. Kerry O'Banion, M.D., Ph.D., a professor in the University of Rochester Medical Center (URMC) Department of Neurobiology and Anatomy and the senior author of the study. "The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognized. However, this study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with Alzheimer's disease."

While space is full of radiation, the earth's magnetic field generally protects the planet and people in low earth orbit from these particles. However, once astronauts leave orbit, they are exposed to constant shower of various radioactive particles. With appropriate warning, astronauts can be shielded from dangerous radiation associated with solar flares. But there are also other forms of cosmic radiation that, for all intents and purposes, cannot be effectively blocked.

Because this radiation exists in low levels, the longer an astronaut is in deep space, the greater the exposure. This is a concern for NASA as the agency is planning manned missions to a distant asteroid in 2021 and to Mars in 2035. The round trip to the red planet, in particular, could take as long as three years.

For over 25 years, NASA has been funding research to determine the potential health risks of space travel in an effort to both develop countermeasures and determine whether or not the risks warranted sending men and women on extended missions in deep space.

Since that time, several studies have demonstrated the potential cancer, cardiovascular, and musculoskeletal impact of galactic cosmic radiation. The study out today for the first time examines the potential impact of space radiation on neurodegeneration, in particular, the biological processes in the brain that contribute to the development of Alzheimer's disease. O'Banion -- whose research focuses on how radiation affects the central nervous system -- and his team have been working with NASA for over eight years.

The researchers studied the impact of a particular form of radiation called high-mass, high-charged (HZE) particles. These particles -- which are propelled through space at very high speeds by the force of exploding stars -- come in many different forms. For this study the researcher chose iron particles. Unlikely hydrogen protons, which are produced by solar flares, the mass of HZE particles like iron, combined with their speed, enable them to penetrate solid objects such as the wall and protective shielding of a spacecraft.

"Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them," said O'Banion. "One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete."

A portion of the research was conducted at the NASA Space Radiation Laboratory at Brookhaven National Laboratory on Long Island. NASA located its research operation at Brookhaven to take advantage of the Lab's particle accelerators which -- by colliding matter together at very high speeds -- can reproduce the radioactive particles found in space.

The researchers specifically wanted to examine whether or not radiation exposure had the potential to accelerate the biological and cognitive indicators of Alzheimer's disease, particularly in individuals who may be predisposed to developing the disease. To accomplish this they chose study the impact on animal models of Alzheimer's disease. These particular models have been extensively studied and scientists understand the precise timeframe in which the disease progresses over time.

At Brookhaven, the animals were exposed to various doses of radiation, including levels comparable to what astronauts would be experience during a mission to Mars. Back in Rochester, a team of researchers -- including URMC graduate student Jonathan Cherry, who was first author on the paper -- evaluated the cognitive and biological impact of the exposure. The mice underwent a series of experiments during which they had to recall objects or specific locations. The researchers observed that mice exposed to radiation were far more likely to fail these tasks -- suggesting neurological impairment -- earlier than these symptoms would typically appear.

The brains of the mice also showed signs of vascular alterations and a greater than normal accumulation of beta amyloid, the protein "plaque" that accumulates in the brain and is one of the hallmarks of the disease.

"These findings clearly suggest that exposure to radiation in space has the potential to accelerate the development of Alzheimer's disease," said O'Banion. "This is yet another factor that NASA, which is clearly concerned about the health risks to its astronauts, will need to take into account as it plans future missions."

Additional co-authors include Jacqueline Williams, Ph.D. and John Olschowka, Ph.D. with URMC and Bin Liu, Ph.D., Jeffrey Frost, and Cynthia Lemere, Ph.D. with Harvard Medical School. The study was funded by NASA.

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Jonathan D. Cherry, Bin Liu, Jeffrey L. Frost, Cynthia A. Lemere, Jacqueline P. Williams, John A. Olschowka, M. Kerry O’Banion. Galactic Cosmic Radiation Leads to Cognitive Impairment and Increased Aß Plaque Accumulation in a Mouse Model of Alzheimer’s Disease. PLoS ONE, 2012; 7 (12): e53275 DOI: 10.1371/journal.pone.0053275

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Decision to give a group effort in the brain

Dec. 23, 2012 — 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.

The research was supported by grants from the Ruth K. Broad Biomedical Foundation, Canadian Institutes of Health Research, National Institute of Mental Health (MH095894), and Department of Defense (W81XWH-11-1-0584).

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Steve W C Chang, Jean-François Gariépy, Michael L Platt. Neuronal reference frames for social decisions in primate frontal cortex. Nature Neuroscience, 2012; DOI: 10.1038/nn.3287

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Italian wolves prefer pork to venison

Dec. 20, 2012 — Some European wolves have a distinct preference for wild boar over other prey, according to new research.

Scientists from Durham University, UK, in collaboration with the University of Sassari in Italy, found that the diet of wolves was consistently dominated by the consumption of wild boar which accounted for about two thirds of total prey biomass, with roe deer accounting for around a third.

The study analysed the remains of prey items in almost 2000 samples of wolf dung over a nine year period and revealed that an increase in roe deer in the wolf diet only occurred in years when boar densities were very low. In years of high roe deer densities, the wolves still preferred to catch wild boar.

The results are published in the journal PLOS ONE.

The research team related the prey remains in wolf dung to the availability of possible prey in part of Tuscany, Italy -- an area recently colonised by wolves. The findings have implications for wildlife conservation as the impact of changing predator numbers on prey species is important for managing populations of both predators and prey.

Lead author, Miranda Davis, from the School of Biological and Biomedical Sciences at Durham University, said: "Our research demonstrates a consistent selection for wild boar among wolves in the study area, which could affect other prey species such as roe deer."

"Intriguingly, in other parts of Europe where red deer are also available, wolves appear to prefer this prey to wild boar, suggesting that they discriminate between different types of venison."

In Europe, the wolf (Canis lupis) is recovering from centuries of persecution and the expansion of wolf populations has the potential to change the ecology of communities of ungulates (hooved animals) by exposing them to natural predation by wolves, according to the researchers.

The preference for boar is in contrast to other areas of Europe where wolves often avoid boar as prey. One factor may be the relatively smaller size of Mediterranean boar, making them less dangerous to wolves in Mediterranean regions, compared to the larger-sized boar that roam other parts of Europe.

Co-author, Dr Stephen Willis, from the School of Biological and Biomedical Sciences at Durham University, said: "Wolves were hunted to extinction in the UK, probably by the end of the 17th century. Our findings from Italy suggest that if they were reintroduced into an area with a healthy ungulate population their impact on livestock could be minimal."

Tuscany's woodlands support populations of both roe deer and wild boar, and are also grazed by sheep, goats and cattle; however, wild boar and roe deer made up over 95 per cent of wolf diet in the study area, with very little evidence of livestock predation.

The scientists identified prey items from fragments of bones and hair in the wolf dung collected in the region. The prey categories included wild boar, roe deer, red deer, hare, small rodents, goats, sheep and cattle.

For more than five years of the study, the percentage of wolf diet made up of wild boar was more than twice that of roe deer. Other prey represented only a very small proportion of the diet.

The researchers believe that further dietary studies are essential for understanding the true impact of wolves on European wildlife over time.

Co-author, Dr Phil Stephens, from the School of Biological and Biomedical Sciences at Durham University added: "Wolves and brown bears are gradually returning to their former strongholds in Europe. Understanding the needs of these species, as well as their potential impacts, is going to be fundamental to managing that welcome return."

The project was part-funded by a Durham University Doctoral Fellowship and the Regional Government of Tuscany and the Province of Arezzo also provided logistical support throughout the study.

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Miranda L. Davis, Philip A. Stephens, Stephen G. Willis, Elena Bassi, Andrea Marcon, Emanuela Donaggio, Claudia Capitani, Marco Apollonio. Prey Selection by an Apex Predator: The Importance of Sampling Uncertainty. PLoS ONE, 2012; 7 (10): e47894 DOI: 10.1371/journal.pone.0047894

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Hawaiian Islands are dissolving from within, study says

Dec. 21, 2012 — Most of us think of soil erosion as the primary force that levels mountains, however geologists have found that Oahu's mountains are dissolving from within due to groundwater.

Someday, Oahu's Koolau and Waianae mountains will be reduced to nothing more than a flat, low-lying island like Midway.

But erosion isn't the biggest culprit. Instead, scientists say, the mountains of Oahu are actually dissolving from within.

"We tried to figure out how fast the island is going away and what the influence of climate is on that rate," said Brigham Young University geologist Steve Nelson. "More material is dissolving from those islands than what is being carried off through erosion."

The research pitted groundwater against stream water to see which removed more mineral material. Nelson and his BYU colleagues spent two months sampling both types of sources. In addition, ground and surface water estimates from the U.S. Geological Survey helped them calculate the total quantity of mass that disappeared from the island each year.

"All of the Hawaiian Islands are made of just one kind of rock," Nelson said. "The weathering rates are variable, too, because rainfall is so variable, so it's a great natural laboratory."

Forecasting the island's future also needs to account for plate tectonics. As Oahu is pushed northwest, the island actually rises in elevation at a slow but steady rate. You've heard of mountain climbing; this is a mountain that climbs.

According to the researchers' estimates, the net effect is that Oahu will continue to grow for as long as 1.5 million years. Beyond that, the force of groundwater will eventually triumph and the island will begin its descent to a low-lying topography.

Undergraduate student Brian Selck co-authored the study, which appears in the journal Geochimica et Cosmochimica Acta. Unfortunately for him, he joined the project only after the field work in Hawaii took place.

Instead, Selck performed the mineralogical analysis of soil samples in the lab back in Provo. The island's volcanic soil contained at least one surprise in weathered rock called saprolites.

"The main thing that surprised me on the way was the appearance of a large amount of quartz in a saprolite taken from a 1-meter depth," Selck said.

After he graduates from BYU, Selck will pursue a career in hydrogeology. BYU geology professor David Tingey joins Nelson and Selck as a co-author on the new study.

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Stephen T. Nelson, David G. Tingey, Brian Selck. The denudation of ocean islands by ground and surface waters: The effects of climate, soil thickness, and water contact times on Oahu, Hawaii. Geochimica et Cosmochimica Acta, 2013; 103: 276 DOI: 10.1016/j.gca.2012.09.046

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Successful solo rock/pop stars twice as likely to die early as those in a band, study finds

Dec. 19, 2012 — Successful solo rock/pop stars are around twice as likely to die early as those in equally famous bands, indicates research published in the online journal BMJ Open.

And those who died of drug and alcohol problems were more likely to have had a difficult or abusive childhood than those dying of other causes, the findings showed.

The authors included 1489 North American and European rock and pop stars over a 50 year period between 1956 (Elivs Presley) and 2006 (Regina Spektor, The Arctic Monkeys, and Snow Patrol)

Their achievements were determined from international polls and top 40 chart successes, while details of their personal lives/childhoods were drawn from a range of music and official websites, published biographies, and anthologies.

During the 50 year period, 137 (9.2%) famous rock/pop stars died. The average age of death was 45 for North American stars and 39 for those from Europe.

The gap in life expectancy between rock and pop stars and the general population widened consistently until 25 years after fame had been achieved, after which death rates began to approach those of the general population -- but only for European stars.

Solo performers were around twice as likely to die early as those in a band, irrespective of whether they were European (9.8% vs 5.4%) or North American (22.8% vs 10.2%).

A successful solo career may be a proxy for fame, it also raises the question of whether the peer support offered by band-mates may be protective, suggest the authors.

While gender and the age at which fame was reached did not influence life expectancy, ethnicity did, with those from non-white backgrounds more likely to die early. And the chances of survival increased among those achieving fame after 1980.

Nearly half of those who died as a result of drugs, alcohol, or violence had at least one unfavourable factor in their childhoods, compared with one in four of those dying of other causes.

These factors -- referred to as adverse childhood experiences, or ACEs for short -- included physical, sexual, or emotional abuse; living with a chronically depressed, suicidal, mentally or physically ill person; living with a substance abuser; having a close relative in prison; and coming from a broken home or one in which domestic violence featured.

Four out of five dead stars with more than one unfavourable childhood factor died from substance misuse or violence-related causes.

A career as a rock/pop star may be attractive to those escaping an unhappy childhood, but it may also provide the resource to feed a predisposition to unhealthy/risky behaviours, say the authors.

"Pop/rock stars are among the most common role models for children, and surveys suggest that growing numbers aspire to pop stardom," they write. "A proliferation of TV talent shows and new opportunities created by the internet can make this dream appear more achievable than ever."

But they caution: "It is important they [children] recognise that substance use and risk taking may be rooted in childhood adversity rather than seeing them as symbols of success."

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The above story is reprinted from materials provided by BMJ-British Medical Journal.

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M. A. Bellis, K. Hughes, O. Sharples, T. Hennell, K. A. Hardcastle. Dying to be famous: retrospective cohort study of rock and pop star mortality and its association with adverse childhood experiences. BMJ Open, 2012; 2 (6): e002089 DOI: 10.1136/bmjopen-2012-002089

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On-demand synaptic electronics: Circuits that learn and forget

Dec. 20, 2012 — Researchers in Japan and the US propose a nanoionic device with a range of neuromorphic and electrical multifunctions that may allow the fabrication of on-demand configurable circuits, analog memories and digital-neural fused networks in one device architecture.

Synaptic devices that mimic the learning and memory processes in living organisms are attracting avid interest as an alternative to standard computing elements that may help extend Moore's law beyond current physical limits.

However so far artificial synaptic systems have been hampered by complex fabrication requirements and limitations in the learning and memory functions they mimic. Now Rui Yang, Kazuya Terabe and colleagues at the National Institute for Materials Science in Japan and the University of California, Los Angeles, in the US have developed two-, three-terminal WO3-x-based nanoionic devices capable of a broad range of neuromorphic and electrical functions.

In its initial pristine condition the system has very high resistance values. Sweeping both negative and positive voltages across the system decreases this resistance nonlinearly, but it soon returns to its original state indicating a volatile state. Applying either positive or negative pulses at the top electrode introduces a soft-breakdown, after which sweeping both negative and positive voltages leads to non-volatile states that exhibit bipolar resistance and rectification for longer periods of time.

The researchers draw similarities between the device properties -- volatile and non-volatile states and the current fading process following positive voltage pulses -- with models for neural behaviour -- that is, short- and long-term memory and forgetting processes. They explain the behaviour as the result of oxygen ions migrating within the device in response to the voltage sweeps. Accumulation of the oxygen ions at the electrode leads to Schottky-like potential barriers and the resulting changes in resistance and rectifying characteristics. The stable bipolar switching behaviour at the Pt/WO3-x interface is attributed to the formation of the electric conductive filament and oxygen absorbability of the Pt electrode.

As the researchers conclude, "These capabilities open a new avenue for circuits, analog memories, and artificially fused digital neural networks using on-demand programming by input pulse polarity, magnitude, and repetition history."

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The above story is reprinted from materials provided by International Center for Materials Nanoarchitectonics (MANA), via ResearchSEA.

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Rui Yang, Kazuya Terabe, Guangqiang Liu, Tohru Tsuruoka, Tsuyoshi Hasegawa, James K. Gimzewski, Masakazu Aono. On-Demand Nanodevice with Electrical and Neuromorphic Multifunction Realized by Local Ion Migration. ACS Nano, 2012; 6 (11): 9515 DOI: 10.1021/nn302510e

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How songbirds learn to sing: Mathematical model explains how birds correct mistakes to say on key

Dec. 20, 2012 — Scientists studying how songbirds stay on key have developed a statistical explanation for why some things are harder for the brain to learn than others.

"We've built the first mathematical model that uses a bird's previous sensorimotor experience to predict its ability to learn," says Emory biologist Samuel Sober. "We hope it will help us understand the math of learning in other species, including humans."

Sober conducted the research with physiologist Michael Brainard of the University of California, San Francisco.

Their results, showing that adult birds correct small errors in their songs more rapidly and robustly than large errors, were published in the Proceedings of the National Academy of Sciences (PNAS).

Sober's lab uses Bengalese finches as a model for researching the mechanisms of how the brain learns to correct vocal mistakes.

Just like humans, baby birds learn to vocalize by listening to adults. Days after hatching, Bengalese finches start imitating the sounds of adults. "At first, their song is extremely variable and disorganized," Sober says. "It's baby talk, basically."

The young finches keep practicing, listening to their own sounds and fixing any mistakes that occur, until eventually they can sing like their elders.

Young birds, and young humans, make a lot of big mistakes as they learn to vocalize. As birds and humans get older, the variability of mistakes shrinks. One theory contends that adult brains tend to screen out big mistakes and pay more attention to smaller ones.

"To correct any mistake, the brain has to rely on the senses," Sober explains. "The problem is, the senses are unreliable. If there is noise in the environment, for example, the brain may think it misheard and ignore the sensory experience."

The link between variability and learning may explain why youngsters tend to learn faster and why adults are more resistant to change.

"Whether you are an opera singer or a bird, there is always variability in your sounds," Sober says. "When the brain receives an error in pitch, it seems to use this very simple and elegant strategy of evaluating the probability of whether the error was just extraneous 'noise,' a problem reading the signal, or an actual mistake in the vocalization."

The researchers wanted to quantify the relationship between the size of a vocal error, and the probability of the brain making a sensorimotor correction. The experiments were conducted on adult Bengalese finches outfitted with light-weight, miniature headphones.

As a bird sang into a microphone, the researchers used sound-processing equipment to trick the bird into thinking it was making vocal mistakes, by changing the bird's pitch and altering the way the bird heard itself, in real-time.

"When we made small pitch shifts, the birds learned really well and corrected their errors rapidly," Sober says. "As we made the pitch shifts bigger, the birds learned less well, until at a certain pitch, they stopped learning."

The researchers used the data to develop a statistical model for the size of a vocal error and whether a bird learns, including the cut-off point for learning from sensorimotor mistakes. They are now developing additional experiments to test and refine the model.

"We hope that our mathematical framework for how songbirds learn to sing could help in the development of human behavioral therapies for vocal rehabilitation, as well as increase our general understanding of how the brain learns," Sober says.

The research was supported by grants from the National Institute of Deafness and Communications Disorders, the National Institute of Neurological Diseases and Stroke and the National Institute of Mental Health.

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The above story is reprinted from materials provided by Emory University. The original article was written by Carol Clark.

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S. J. Sober, M. S. Brainard. Vocal learning is constrained by the statistics of sensorimotor experience. Proceedings of the National Academy of Sciences, 2012; 109 (51): 21099 DOI: 10.1073/pnas.1213622109

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