It is not fully understood why the brain's cognitive functions such as memory and speech decline as we age. Although work published this year suggests cognitive decline can be detectable before 50 years of age.

The research, led by Professor Andy Randall and Dr Jon Brown from the University's School of Physiology and Pharmacology, identified a novel cellular mechanism underpinning changes to the activity of neurones which may underlie cognitive decline during normal healthy aging.

The brain largely uses electrical signals to encode and convey information. Modifications to this electrical activity are likely to underpin age-dependent changes to cognitive abilities.

The researchers examined the brain's electrical activity by making recordings of electrical signals in single cells of the hippocampus, a structure with a crucial role in cognitive function.

In this way they characterised what is known as "neuronal excitability" - this is a descriptor of how easy it is to produce brief, but very large, electrical signals called action potentials; these occur in practically all nerve cells and are absolutely essential for communication within all the circuits of the nervous system.

Action potentials are triggered near the neurone's cell body and once produced travel rapidly through the massively branching structure of the nerve cell, along the way activating the synapses the nerve cell makes with the numerous other nerve cells to which it is connected.

The Bristol group identified that in the aged brain it is more difficult to make hippocampal neurones generate action potentials.

Furthermore they demonstrated that this relative reluctance to produce action potential arises from changes to the activation properties of membrane proteins called sodium channels, which mediate the rapid upstroke of the action potential by allowing a flow of sodium ions into neurones.

Professor Randall, Professor in Applied Neurophysiology said: "Much of our work is about understanding dysfunctional electrical signalling in the diseased brain, in particular Alzheimer's disease. We began to question, however, why even the healthy brain can slow down once you reach my age. Previous investigations elsewhere have described age-related changes in processes that are triggered by action potentials, but our findings are significant because they show that generating the action potential in the first place is harder work in aged brain cells.

]]> Thu, 09 FEB 2012 09:07:30 AEST Tempe AZ (SPX) Feb 09, 2012 - As an ice age crept upon them thousands of years ago, Neanderthals and modern human ancestors expanded their territory ranges across Asia and Europe to adapt to the changing environment.

In the process, they encountered each other.

Although many anthropologists believe that modern humans ancestors "wiped out" Neanderthals, it's more likely that Neanderthals were integrated into the human gene pool thousands of years ago during the Upper Pleistocene era as cultural and climatic forces brought the two groups together, said Arizona State University Professor C. Michael Barton of the Center for Social Dynamics and Complexity and School of Human Evolution and Social Change.

"The traditional story in textbooks doesn't fit well with what we know about hunter-gatherers. For the most part, they don't like to go far from home. It's dangerous," Barton said.

Barton and Julien Riel-Salvatore of the University of Colorado Denver, present new research in the journal, Advances in Complex Systems, that the Neanderthals demise was due to a combination of influences, including cultural changes.

The paper titled, Agents of Change: Modeling Biocultural Evolution in Upper Pleistocene Western Eurasia, appears online in January. It builds on work published last year in the journal Human Ecology and on recent genetic studies that show a Neanderthal contribution to the modern human genome.

"How a culture's working knowledge is passed on is as important as biological information for human evolution," Barton said. "There is a perception that biological evolution determines culture during the Pleistocene era and that cultural influences predominate afterwards (including today). The reality is that the two forces have been working together and they were as important 50,000 years ago as they are today."

The researchers used archaeological data to track cultural and socio-ecological changes in behavior in Western Eurasia during the past 120,000 years. As Neanderthals and early humans land-use patterns shifted during the last ice age, computer modeling showed that the two populations began to interact and mate, leading to the "extinction" of one of the groups due to hybridization, a well-recognized phenomenon in conservation biology.

Neanderthals were limited to western Eurasia and usually it is the smaller population that becomes "extinct" in this way. Nevertheless, succeeding hybrid populations still carry genes from the regional group that disappeared, according to the researchers.

To address the possibility that the two groups would not have seen one another as potential mates, the researchers also examined the possible impacts of social barriers to mating in their models. They found that unless social taboos were nearly 100 percent effective, it would have not made any difference in outcomes over time as the gene pools mixed, Barton said.

"This is one of the first attempts to explicitly address the impact of various degrees of social avoidance on possible hybridization between the two groups," added Riel-Salvatore.

"Other than the fact that they disappeared, there is no evidence that Neanderthals were any less fit as hunter-gatherers of the late Pleistocene than any other human ancestor living at that time. It looks like they were as capable as anyone else," Barton said.

Barton and Riel-Salvatore studied the stone artifacts that were left behind by these ancient peoples to track the movement patterns among hunter-gatherers across western Eurasia during the Pleistocene era.

"Stone technology is completely different than the kind of technology we have today," Barton said. "But it can tell us important things about land use, how people organized themselves and how they moved to access resources to live."

These tools provide insight into Neanderthals' lives and gene sequencing tells the story of their legacy.

"Recent sequencing of ancient Neanderthal DNA indicates that Neanderthal genes make up from 1 to 4 percent of the genome of modern populations-especially those of European descent," Riel-Salvatore said. "While they disappeared as a distinctive form of humanity, they live on in our genes. What we do in this study is propose one model of how this could have happened and show that behavioral decisions were probably instrumental in this process."

The researchers suggest it's time to study variation and diversity among individuals rather than classify them into types or species.

"Neanderthals' legacy lives on in our biological genome and possibly in our cultural knowledge," Barton added. "There may have been may other populations like Neanderthals who were integrated into a global human species in the Late Pleistocene. We're the results."

]]> Thu, 09 FEB 2012 09:07:30 AEST New Rochelle NY (SPX) Feb 09, 2012 - Innovative magnetic resonance imaging (MRI) techniques that can measure changes in the microstructure of the white matter likely to affect brain function and the ability of different regions of the brain to communicate are presented in an article in the groundbreaking new neuroscience journal Brain Connectivity, a bimonthly peer-reviewed publication from Mary Ann Liebert, Inc.. The article is available free online.

Brain function depends on the ability of different brain regions to communicate through signaling networks that travel along white matter tracts.

Using different types and amounts of tissue staining to measure how water molecules interact with the surrounding brain tissue, researchers can quantify changes in the density, orientation, and organization of white matter. They can then use this information to generate image maps of these signaling networks, a method called tractography.

Andrew Alexander and colleagues from University of Wisconsin, Madison, describe three quantitative MRI (qMRI) techniques that are enabling the characterization of the microstructural properties of white matter: diffusion MRI, magnetization transfer imaging, and relaxometry.

This approach can be used to study and compare the properties of brain tissue across populations and to shed light on mechanisms underlying aging, disease, and gender differences in brain function, for example. The authors present their findings in the article "Characterization of Cerebral White Matter Properties Using Quantitative Magnetic Resonance Imaging Stains."

"White matter is the material that provides for the wiring and connectivity between brain regions. This exciting paper describes three new methodologies to measure the integrity of white matter in normal and diseased brain. These methods show promise in multiple sclerosis, depression, aging, and human development," says Bharat Biswal, PhD, Co-Editor-in-Chief of Brain Connectivity and Associate Professor, University of Medicine and Dentistry of New Jersey.

]]> Thu, 09 FEB 2012 09:07:30 AEST Tubingen, Germany (SPX) Feb 06, 2012 - Holding information within one's memory for a short while is a seemingly simple and everyday task. We use our short-term memory when remembering a new telephone number if there is nothing to write at hand, or to find the beautiful dress inside the store that we were just admiring in the shopping window.

Yet, despite the apparent simplicity of these actions, short-term memory is a complex cognitive act that entails the participation of multiple brain regions. However, whether and how different brain regions cooperate during memory has remained elusive.

A group of researchers from the Max Planck Institute for Biological Cybernetics in Tubingen, Germany have now come closer to answering this question. They discovered that oscillations between different brain regions are crucial in visually remembering things over a short period of time.

It has long been known that brain regions in the frontal part of the brain are involved in short-term memory, while processing of visual information occurs primarily at the back of the brain. However, to successfully remember visual information over a short period of time, these distant regions need to coordinate and integrate information.

To better understand how this occurs, scientists from the Max Planck Institute of Biological Cybernetics in the department of Nikos Logothetis recorded electrical activity both in a visual area and in the frontal part of the brain in monkeys.

The scientists showed the animals identical or different images within short intervals while recording their brain activity. The animals then had to indicate whether the second image was the same as the first one.

The scientists observed that, in each of the two brain regions, brain activity showed strong oscillations in a certain set of frequencies called the theta-band. Importantly, these oscillations did not occur independently of each other, but synchronized their activity temporarily: "It is as if you have two revolving doors in each of the two areas. During working memory, they get in sync, thereby allowing information to pass through them much more efficiently than if they were out of sync," explains Stefanie Liebe, the first author of the study, conducted in the team of Gregor Rainer in cooperation with Gregor Horzer from the Technical University Graz.

The more synchronized the activity was, the better could the animals remember the initial image. Thus, the authors were able to establish a direct relationship between what they observed in the brain and the performance of the animal.

The study highlights how synchronized brain oscillations are important for the communication and interaction of different brain regions. Almost all multi-faceted cognitive acts, such as visual recognition, arise from a complex interplay of specialized and distributed neural networks.

How relationships between such distributed sites are established and how they contribute to represent and communicate information about external and internal events in order to attain a coherent percept or memory is still poorly understood.

]]> Thu, 09 FEB 2012 09:07:30 AEST Washington (AFP) Feb 1, 2012 - US scientists said Wednesday they have found a way to decode how the brain hears words, in what researchers described as a major step toward one day helping people communicate after paralysis or stroke.

By placing electrodes on the brains of research subjects and then having them listen to conversations, scientists were able to analyze the sound frequencies registered and figure out which words they were hearing.

"We were focused on how the brain processes the sounds of speech," researcher Brian Pasley of the Helen Wills Neuroscience Institute at the University of California Berkeley told AFP.

"Most of the information in speech is between one to 8,000 hertz. Essentially the brain analyzes those different sound frequencies in somewhat separate locations."

By tracking how and where the brain registered sounds in the temporal lobe -- the center of the auditory system -- scientists were able to map out the words and then recreate them as heard by the brain.

"When a particular brain site is being activated, we know that roughly corresponds to some sound frequency that the patient is actually listening to," Pasley said.

"So we could map that out to an extent that would allow us to use that brain activity to resynthesize the sound from the frequencies we were guessing."

One word the researchers mapped was "structure." The high-frequency "s" sound showed up as a certain pattern in the brain, while the lower harmonics of the "u" sound appeared as a different pattern.

"There is to some extent a correspondence between these features of sound and the brain activity that they cause," and putting together the physical registry in the brain helped rebuild the words, Pasley explained.

The work builds on previous research in ferrets, in which scientists read to the animals and recorded their brain activity.

They were able to decode which words the creatures heard even though the ferrets themselves didn't understand the words.

The next step for researchers is to figure out just how similar the process of hearing sounds may be to the process of imagining words and sounds.

That information could one day help scientists determine what people want to say when they cannot physically speak.

Some previous research has suggested there may be similarities, but much more work needs to be done, Pasley said.

"This is huge for patients who have damage to their speech mechanisms because of a stroke or Lou Gehrig's disease and can't speak," co-author Robert Knight, a UC Berkeley professor of psychology and neuroscience, said in a statement.

"If you could eventually reconstruct imagined conversations from brain activity, thousands of people could benefit."

Participating researchers came from the University of Maryland, UC Berkeley and Johns Hopkins University in Baltimore, Maryland.

The study appears in the January 31 edition of the open access journal PLoS Biology.

]]> Thu, 09 FEB 2012 09:07:30 AEST Kansas City, MO (SPX) Feb 02, 2012 - Memories in our brains are maintained by connections between neurons called "synapses". But how do these synapses stay strong and keep memories alive for decades?

Neuroscientists at the Stowers Institute for Medical Research have discovered a major clue from a study in fruit flies: Hardy, self-copying clusters or oligomers of a synapse protein are an essential ingredient for the formation of long-term memory.

The finding supports a surprising new theory about memory, and may have a profound impact on explaining other oligomer-linked functions and diseases in the brain, including Alzheimer's disease and prion diseases.

"Self-sustaining populations of oligomers located at synapses may be the key to the long-term synaptic changes that underlie memory; in fact, our finding hints that oligomers play a wider role in the brain than has been thought," says Kausik Si, Ph.D., an associate investigator at the Stowers Institute, and senior author of the new study, which is published in the January 27, 2012 online issue of the journal Cell.

Si's investigations in this area began nearly a decade ago during his doctoral research in the Columbia University laboratory of Nobel-winning neuroscientist Eric Kandel.

He found that in the sea slug Aplysia californica, which has long been favored by neuroscientists for memory experiments because of its large, easily-studied neurons, a synapse-maintenance protein known as CPEB (Cytoplasmic Polyadenylation Element Binding protein) has an unexpected property.

A portion of the structure is self-complementary and-much like empty egg cartons-can easily stack up with other copies of itself. CPEB thus exists in neurons partly in the form of oligomers, which increase in number when neuronal synapses strengthen.

These oligomers have a hardy resistance to ordinary solvents, and within neurons may be much more stable than single-copy "monomers" of CPEB. They also seem to actively sustain their population by serving as templates for the formation of new oligomers from free monomers in the vicinity.

CPEB-like proteins exist in all animals, and in brain cells they play a key role in maintaining the production of other synapse-strengthening proteins.

Studies by Si and others in the past few years have hinted that CPEB's tendency to oligomerize is not merely incidental, but is indeed essential to its ability to stabilize longer-term memory. "What we've lacked till now are experiments showing this conclusively," Si says.

In the new study, Si and his colleagues examined a Drosophila fruit fly CPEB protein known as Orb2. Like its counterpart in Aplysia, it forms oligomers within neurons.

"We found that these Orb2 oligomers become more numerous in neurons whose synapses are stimulated, and that this increase in oligomers happens near synapses," says lead author Amitabha Majumdar, Ph.D., a postdoctoral researcher in Si's lab.

The key was to show that the disruption of Orb2 oligomerization on its own impairs Orb2's function in stabilizing memory. Majumdar was able to do this by generating an Orb2 mutant that lacks the normal ability to oligomerize yet maintains a near-normal concentration in neurons. Fruit flies carrying this mutant form of Orb2 lost their ability to form long-term memories.

"For the first 24 hours after a memory-forming stimulus, the memory was there, but by 48 hours it was gone, whereas in flies with normal Orb2 the memory persisted," Majumdar says.

Si and his team are now following up with experiments to determine for how long Orb2 oligomers are needed to keep a memory alive. "We suspect that they need to be continuously present, because they are self-sustaining in a way that Orb2 monomers are not," says Si.

The team's research also suggests some intriguing possibilities for other areas of neuroscience. This study revealed that Orb2 proteins in the Drosophila nervous system come in a rare, highly oligomerization-prone form (Orb2A) and a much more common, much less oligomerization-prone form (Orb2B).

"The rare form seems to be the one that is regulated, and it seems to act like a seed for the initial oligomerization, which pulls in copies of the more abundant form," Si says. "This may turn out to be a basic pattern for functional oligomers."

The findings may help scientists understand disease-causing oligomers too. Alzheimer's, Parkinson's and Huntington's disease, as well as prion diseases such as Creutzfeldt-Jakob disease, all involve the spread in the brain of apparently toxic oligomers of various proteins. One such protein, strongly implicated in Alzheimer's disease, is amyloid beta; like Orb2 it comes in two forms, the highly oligomerizing amyloid-beta-42 and the relatively inert amyloid-beta-40.

Si's work hints at the possibility that oligomer-linked diseases are relatively common in the brain because the brain evolved to be relatively hospitable to CPEB proteins and other functional oligomers, and thus has fewer mechanisms for keeping rogue oligomers under control.

Other researchers who contributed to the work include Wanda Colon Cesario, Erica White-Grindely, Huoqin Jian, Fangzhen Ren, Mohammed 'Repon' Khan, Liying Li, Edward Man-Lik Choi, Kasthuri Kannan, Feng Li, Jay Unruh and Brian Slaughter at the Stowers Institute for Medical Research in Kansas City, Missouri.

]]> Thu, 09 FEB 2012 09:07:30 AEST Berkeley CA (SPX) Feb 02, 2012 - Neuroscientists may one day be able to hear the imagined speech of a patient unable to speak due to stroke or paralysis, according to University of California, Berkeley, researchers.

These scientists have succeeded in decoding electrical activity in the brain's temporal lobe - the seat of the auditory system - as a person listens to normal conversation. Based on this correlation between sound and brain activity, they then were able to predict the words the person had heard solely from the temporal lobe activity.

"This is huge for patients who have damage to their speech mechanisms because of a stroke or Lou Gehrig's disease and can't speak," said co-author Robert Knight, a UC Berkeley professor of psychology and neuroscience.

"If you could eventually reconstruct imagined conversations from brain activity, thousands of people could benefit."

"This research is based on sounds a person actually hears, but to use it for reconstructing imagined conversations, these principles would have to apply to someone's internal verbalizations," cautioned first author Brian N. Pasley, a post-doctoral researcher in the center.

"There is some evidence that hearing the sound and imagining the sound activate similar areas of the brain. If you can understand the relationship well enough between the brain recordings and sound, you could either synthesize the actual sound a person is thinking, or just write out the words with a type of interface device."

In addition to the potential for expanding the communication ability of the severely disabled, he noted, the research also "is telling us a lot about how the brain in normal people represents and processes speech sounds."

Pasley and his colleagues at UC Berkeley, UC San Francisco, University of Maryland and The Johns Hopkins University report their findings Jan. 31 in the open-access journal PLoS Biology.

Help from epilepsy patients
They enlisted the help of people undergoing brain surgery to determine the location of intractable seizures so that the area can be removed in a second surgery. Neurosurgeons typically cut a hole in the skull and safely place electrodes on the brain surface or cortex - in this case, up to 256 electrodes covering the temporal lobe - to record activity over a period of a week to pinpoint the seizures. For this study, 15 neurosurgical patients volunteered to participate.

Pasley visited each person in the hospital to record the brain activity detected by the electrodes as they heard 5-10 minutes of conversation. Pasley used this data to reconstruct and play back the sounds the patients heard. He was able to do this because there is evidence that the brain breaks down sound into its component acoustic frequencies - for example, between a low of about 1 Hertz (cycles per second) to a high of about 8,000 Hertz -that are important for speech sounds.

Pasley tested two different computational models to match spoken sounds to the pattern of activity in the electrodes. The patients then heard a single word, and Pasley used the models to predict the word based on electrode recordings.

"We are looking at which cortical sites are increasing activity at particular acoustic frequencies, and from that, we map back to the sound," Pasley said. He compared the technique to a pianist who knows the sounds of the keys so well that she can look at the keys another pianist is playing in a sound-proof room and "hear" the music, much as Ludwig van Beethoven was able to "hear" his compositions despite being deaf.

The better of the two methods was able to reproduce a sound close enough to the original word for Pasley and his fellow researchers to correctly guess the word.

"We think we would be more accurate with an hour of listening and recording and then repeating the word many times," Pasley said. But because any realistic device would need to accurately identify words heard the first time, he decided to test the models using only a single trial.

"This research is a major step toward understanding what features of speech are represented in the human brain" Knight said. "Brian's analysis can reproduce the sound the patient heard, and you can actually recognize the word, although not at a perfect level."

Knight predicts that this success can be extended to imagined, internal verbalizations, because scientific studies have shown that when people are asked to imagine speaking a word, similar brain regions are activated as when the person actually utters the word.

"With neuroprosthetics, people have shown that it's possible to control movement with brain activity," Knight said. "But that work, while not easy, is relatively simple compared to reconstructing language. This experiment takes that earlier work to a whole new level."

Based on earlier work with ferrets
The current research builds on work by other researchers about how animals encode sounds in the brain's auditory cortex. In fact, some researchers, including the study's coauthors at the University of Maryland, have been able to guess the words ferrets were read by scientists based on recordings from the brain, even though the ferrets were unable to understand the words.

The ultimate goal of the UC Berkeley study was to explore how the human brain encodes speech and determine which aspects of speech are most important for understanding.

"At some point, the brain has to extract away all that auditory information and just map it onto a word, since we can understand speech and words regardless of how they sound," Pasley said.

"The big question is, What is the most meaningful unit of speech? A syllable, a phone, a phoneme? We can test these hypotheses using the data we get from these recordings."

]]> Thu, 09 FEB 2012 09:07:30 AEST Washington DC (SPX) Feb 01, 2012 - Pouring at least one glass of milk each day could not only boost your intake of much-needed key nutrients, but it could also positively impact your brain and mental performance, according to a recent study in the International Dairy Journal.

Researchers found that adults with higher intakes of milk and milk products scored significantly higher on memory and other brain function tests than those who drank little to no milk. Milk drinkers were five times less likely to "fail" the test, compared to non milk drinkers.

Researchers at the University of Maine put more than 900 men and women ages 23 to 98 through a series of brain tests - including visual-spatial, verbal and working memory tests - and tracked the milk consumption habits of the participants.

In the series of eight different measures of mental performance, regardless of age and through all tests, those who drank at least one glass of milk each day had an advantage.

The highest scores for all eight outcomes were observed for those with the highest intakes of milk and milk products compared to those with low and infrequent milk intakes.

The benefits persisted even after controlling for other factors that can affect brain health, including cardiovascular health and other lifestyle and diet factors. In fact, milk drinkers tended to have healthier diets overall, but there was something about milk intake specifically that offered the brain health advantage, according to the researchers.

In addition to the many established health benefits of milk from bone health to cardiovascular health, the potential to stave off mental decline may represent a novel benefit with great potential to impact the aging population.

While more research is needed, the scientists suggest some of milk's nutrients may have a direct effect on brain function and that "easily implemented lifestyle changes that individuals can make present an opportunity to slow or prevent neuropsychological dysfunction."

New and emerging brain health benefits are just one more reason to start each day with lowfat or fat free milk. Whether in a latte, in a smoothie, on your favorite cereal, or straight from the glass, milk at breakfast can be a key part of a healthy breakfast that help sets you up for a successful day.

The 2010 Dietary Guidelines for Americans recommend three glasses of lowfat or fat free milk daily for adults and each 8-ounce glass contains nine essential nutrients Americans need, including calcium and vitamin D.

Crichton GE, Elias MF, Dore GA, Robbins MA. Relation between dairy food intake and cognitive function: The Maine-Syracuse Longitudinal Study. International Dairy Journal. 2012; 22:15-23.

]]> Thu, 09 FEB 2012 09:07:30 AEST Washington DC (SPX) Jan 30, 2012 - The timing and pattern of the migration of early modern humans has been a source of much debate and research. Now, a new study uses genetic analysis to look for clues about the migration of the first modern humans who moved out of Africa more than 60,000 years ago.

The research, published January 26 by Cell Press in the American Journal of Human Genetics, the official journal of the American Society of Human Genetics, provides intriguing insight into the earliest stages of human migration and suggests that modern humans settled in Arabia on their way from the Horn of Africa to the rest of the world.

"A major unanswered question regarding the dispersal of modern humans around the world concerns the geographical site of the first steps out of Africa," explains senior study author, Dr. Luisa Pereira from the Institute of Molecular Pathology and Immunology of the University of Porto in Portugal (IPATIMUP).

"One popular model predicts that the early stages of the dispersal took place across the Red Sea to southern Arabia, but direct genetic evidence has been thin on the ground."

The work, led by Dr. Pereira at IPATMUP and Professor Martin Richards at the University of Leeds in the UK, in collaboration with colleagues from across Europe, Arabia, and North Africa, explored this question by analyzing three of the earliest non-African maternal lineages.

These early branches are associated with the time period when modern humans first successfully moved out of Africa.

The team compared complete mitochondrial DNA genomes from Arabia and the Near East with a database of hundreds more samples from Europe. Mitochondrial DNA traces the female line of descent and is useful for comparing the relatedness between different populations.

The researchers found evidence for an ancient ancestry within Arabia. Professor Richards, who is now Professor of Archaeogenetics at the University of Huddersfield, concludes: "Taken together, our results suggest that Arabia was indeed the first staging-post in the spread of modern humans around the world."

]]> Thu, 09 FEB 2012 09:07:30 AEST Tokyo (AFP) Jan 30, 2012 - Japan's population is expected to shrink to a third of its current size over the next century, with the average woman living to over 90 within 50 years, a government report said Monday.

The population is forecast to decline from the current 127.7 million to 86.7 million by 2060 and to tumble again to 42.9 million by 2110 "if conditions remain unchanged", the health and welfare ministry said in the report.

The projections by the ministry's National Institute of Population and Social Security Research forecast that Japanese women would on average have just 1.35 babies, well below the replacement rate, within 50 years.

The report said that last year's earthquake and tsunami in northeastern Japan, which left more than 19,000 people dead or missing, hit average life expectancy but that the figure was expected to continue its upward trend.

Japan's life expectancy -- one of the highest in the world -- is expected to rise from 86.39 years in 2010 to 90.93 years in 2060 for women and from 79.64 years to 84.19 years for men.

In September the government announced that the number of people aged 100 or older hit a record high for the 41st consecutive year.

The health ministry said 37 out of every 100,000 people in the country are now centenarians -- a total of more than 47,700, with 87 percent of them women. The figure was more than 3,300 higher than in 2010.

More than 20 percent of Japan's population are aged 65 or over, one of the highest proportions in the world.

Japan's population has been declining as many young people have put off starting families, seeing it as a burden on their lifestyles and careers. A slow economy has also discouraged young people from having babies.

Analysts say having a smaller population is not in itself a problem, as demonstrated by the economic and diplomatic successes of many European nations with far fewer people than Japan.

But an ageing population causes all manner of difficulties, most notably for Japan's government finances, already hard pressed by two decades of economic stagnation.

More retirees inevitably means more spending on social security when Japan's public debt, at twice GDP, is already one of the industrialised world's worst.

]]> Thu, 09 FEB 2012 09:07:30 AEST Subscribe to our daily selection of space, military, environment and energy newsletters responseText http://visitor.constantcontact.com/manage/optin/ea?v=0016gbbKsaiGSpQFojVO8ZoHw%3D%3D