Tuesday, May 8, 2012

779. Cuba's Success with AIDS Epidemic and New Challenges


By Donald McNeil Jr., The New York Times, May 7, 2012

Juan Carlos Miranda, an AIDS patient, with Dr. Victor Maracha
at an AIDS treatment sanitarium near Havana.
Photo credit: Jose Goitia 
HAVANA — Yudelsy García O’Connor, the first baby known to have been born with H.I.V. in Cuba, is not merely still alive. She is vibrant, funny and, at age 25, recently divorced but hoping to remarry and have children.

Her father died of AIDS when she was 10, her mother when she was 23. She was near death herself in her youth.
“I’m not afraid of death,” she said. “I know it could knock on my door. It comes for everyone. But I take my medicine.”
Ms. García is alive thanks partly to lucky genes, and partly to the intensity with which Cuba has attacked its AIDS epidemic. Whatever debate may linger about the government’s harsh early tactics — until 1993, everyone who tested positive for H.I.V. was forced into quarantine — there is no question that they succeeded.
Cuba now has one of the world’s smallest epidemics, a mere 14,038 cases. Its infection rate is 0.1 percent, on par with Finland, Singapore and Kazakhstan. That is one-sixth the rate of the United States, one-twentieth of nearby Haiti.
The population of Cuba is only slightly larger than that of New York City. In the three decades of the global AIDS epidemic, 78,763 New Yorkers have died of AIDS. Only 2,364 Cubans have.
Other elements have contributed to Cuba’s success: It has free universal basic health care; it has stunningly high rates of H.I.V. testing; it saturates its population with free condoms, concentrating on high-risk groups like prostitutes; it gives its teenagers graphic safe-sex education; it rigorously traces the sexual contacts of each person who tests positive.
By contrast, the response in the United States — which records 50,000 new infections every year — seems feeble. Millions of poor people never see a doctor. Testing is voluntary, and many patients do not return for their results. Sex education is so politicized that many schools teach nothing about protected sex; condoms are expensive, and distribution of free ones is haphazard.
Cuba has succeeded even though it has the most genetically diverse epidemic outside Africa. Almost all American cases are of one strain, subtype B. Cuba has 21 different strains.
The genetic diversity is a legacy of its foreign aid. Since the 1960s, Cuba has sent abroad thousands of “internationalists” — soldiers, doctors, teachers and engineers. Stationed all over Africa, they brought back a wide array of strains. According to a study in 2002, 11 of Cuba’s 21 strains are unknown elsewhere, formed when two others mixed.
And Cuba’s success has come despite its being a sex tourism destination for Europeans and Canadians.
While the police enforce laws against overt streetwalking, bars and hotel lobbies in downtown Havana are filled with young women known as jineteras — slang for “jockeys” — who approach foreigners, asking if they would like to go for a drink, or perhaps dancing, with the unspoken assumption that it will lead to more. Even so, of the roughly 1,000 new infections diagnosed each year, 81 percent are among men and very few among young unmarried women.
“Most of those who sleep with tourists know to use condoms,” said Dr. Ribero Wong, an AIDS specialist here.
In a survey in 2009, 77 percent of all sex workers said they regularly used condoms.
There are male jineteras for gay tourists too, of course, “but we believe the main vector is within the people,” said Dr. Luis Estruch Rancaño, deputy minister for public health. “Mainly, the very promiscuous group in the homosexual community who have many partners and don’t take precautions.”
One example is Carlos Emilio García, 50, a registered nurse who lives and works at a former quarantine sanitarium outside Havana. He had negative H.I.V. tests at his job every six months from 1990 to 1996, but became infected in 1997.
He admits to having had many partners; as he put it, “No, I don’t know who my assassin is.”
Asked why a well-educated nurse would risk sex without a condom, he waved his hands in the air and replied, “You know — because we all do crazy things sometimes.”
The few Cuban women who are infected usually get the virus from partners who are secretly bisexual, experts said.

“Homo-bisexual transmission” is its own category in Cuba; socially, a man who occasionally has sex with other men is not considered gay if he is a “top” — the penetrative partner, explained Ramón Arango García, a fashion designer and educator at the National AIDS and Sexually Transmitted Disease Prevention Center.

Heroin use, which drives epidemics in many countries, is virtually nonexistent in Cuba, officials insist.
And since 1986, only 38 babies have been born with the virus. In Cuba’s cradle-to-grave health care system, pregnant women get up to 12 free prenatal checkups, during which they are tested for H.I.V. at least twice.
Before antiretroviral drugs were available, H.I.V.-infected women were offered abortions or, if they chose to deliver, Caesareans and free infant formula to discourage breast-feeding and reduce the risk of transmission. Now they get the drugs free.
Universal Coverage
As broken as it is economically, Cuba still points proudly to one legacy of its 1959 revolution: Basic health care is universal and free. Cuba has 535,000 health care workers (“We’re all either doctors or baseball players,” one hospital microbiologist joked) and each citizen is officially registered with a family doctor nearby; if a patient skips a checkup, the doctor is expected to find out why.
“I was trained to expect my patients to come to me,” said Dr. Rafael Mazín, senior AIDS adviser for the Pan American Health Organization in Washington, who is Mexican. “In Cuba, the doctor comes to you.”
Cuba is tied with the United States in both life expectancy and infant mortality.
Dr. Jorge Pérez Ávila is Cuba’s Tony Fauci, its best-known AIDS doctor. He is grandfatherly now, and clearly much loved by former patients like Ms. García, but he has memories of helping his bus driver father make gasoline bombs to throw at the police during the Batista government. As a teenager he dropped out of school to live in the mountains, teaching villagers to read under a literacy program after Castro came to power.
He treated Ms. García’s parents on their deathbeds and heard her father beg, “Do whatever it takes to help my daughter live.” (Her father, who had been a soldier in Angola, was a truck driver. He had nine girlfriends in different towns, five of whom he infected.)
Many medical authorities agree that Cuba had an early and effective response to the epidemic. In his book, “AIDS: Confessions to a Doctor,” published only in Spanish, Dr. Pérez gave his account of the meeting that galvanized Cuba’s response.
In 1983, Fidel Castro visited the Pedro Kourí Institute, Cuba’s top tropical disease hospital, to hear a presentation on malaria and dengue fever.
As it ended, he suddenly asked the director, “Gustavo, what are you doing to keep AIDS from entering Cuba?”
Dr. Gustavo Kourí, son of the institute’s founder, was caught off guard, Dr. Pérez said, and stammered: “AIDS, comandante? AIDS? It is a new disease. We don’t even know whether it’s produced by a bacteria, a virus or a fungus. There isn’t much data on it, just what’s been reported in the United States and a few cases in Europe. It will take time to know how big it is.”
Mr. Castro replied: “I think it will be the epidemic of this century. And it’s your responsibility, Gustavo, to stop it becoming a major problem here.”
This was two years before any American president publicly uttered the word “AIDS.” Asked how Mr. Castro could have been so prescient, Dr. Pérez struggled to find the right word, then said: “Castro has luz larga” — “big lights,” the Cuban slang for automobile high beams. “He reads a lot. He sees far ahead.”
Dr. Pérez is simultaneously both a fan of the Castro government and a bit of a cynic; on Dec. 1, he led a “Viva, Fidel!” cheer at his hospital’s World AIDS Day. But he also mentioned that Mr. Castro once praised him by saying: “Jorge, I’ve been reading your mail. Your patients say very nice things about you.”
The medical establishment reacted quickly. The first step was to throw out all imported blood — 20,000 units. That avoided the devastation that the hemophiliac populations in the United States and France suffered.
Doctors were sent to Brazil and France to study cases.
All of the country’s family doctors were ordered to watch for infections that indicate AIDS like Kaposi’s sarcoma or Pneumocystis carinii pneumonia.
Because there was no H.I.V. test yet, the first cases were found late in the disease, leading doctors to think most patients died within a year — an erroneous assumption that helped justify the quarantine policy.
In 1986, blocked by the embargo from buying American test kits, Cuba bought 750,000 French ones.
According to Dr. María Isela Lantero, AIDS chief at the Health Ministry’s, Cuba’s 11 million citizens have been tested 43 million times; last year, more than two million tests were done. That is the equivalent of testing the sexually active population every three years, though in reality the focus is on high-risk groups, who are tested more often.
Cubans returning from abroad are routinely tested, as are pregnant women, prisoners, soldiers, hospital patients, health workers and anyone treated for venereal disease. So is anyone whose family doctor suspects he or she is gay, a sex worker or otherwise at risk.
Haydee Martínez Obregón, 33, who has lived in the AIDS sanitarium in Sancti Spíritus, in central Cuba, since she was 19, is an example of that. (She lives there by choice, she said, because she has no home outside.)

Asked how she learned she was infected, she said, “My family doctor thought it was a good idea to test me because I was so promiscuous.”
And how did he know that?
“My mother told him everything.”
Anonymous voluntary testing is also available at 700 clinics and hospitals.Anyone who tests positive gets an appointment with an epidemiology nurse, who asks for the names of everyone he or she has ever slept with.
By law, answering is voluntary.
“If they say no, nothing happens,” Dr. Pérez said.
But pressure is clearly applied. A patient who says no to the nurse gets an appointment with the doctor, then with a social worker and then sometimes with a psychologist. Then a team of H.I.V.-positive educators will make a home visit. So might the local Committee for the Defense of the Revolution. Depending on whom one asks, those committees are the defenders of Cuban democracy, domestic spies or just state-sponsored Nosy Parkers.
Some still refuse. Arachu Castro, a professor of global health at Harvard Medical School who often works in Cuba, described one woman who absolutely insisted that she had never slept with anyone but her husband, who was virus-free.
“We called her the Immaculate Infection,” she said.
There are other subtle pressures, Dr. Castro said. Socialist education teaches Cubans to feel responsible for one another. Also, most Cubans subsist partly on government rations and the sick get extra food, and their lifesaving drugs, from the government.
Everyone who tests positive also must take a two-week course in “living responsibly with H.I.V.”
Rising Challenge
With mandatory quarantine long gone and the virus now mostly in gay and bisexual men, new infections are slowly but steadily rising. They now approach 1,000 a year, “and we’re waiting for the plateau,” said Dr. José Joanes Fiol, the Health Ministry’s chief epidemiologist.
Today, condoms and sex education are the chief weapons.
Cuban society is the opposite of puritanical; scanty clothing is routine, suggestive flirtation is common, and so are divorce and extramarital affairs.
The government distributes more than 100 million condoms a year. Every place with young customers, even pizzerias, is required to stock them.
“The first ones we got were from China, and had butterflies and penguins on the package,” Manuel Hernández Fernández, an AIDS educator for 25 years, said with a snort. “We had to Cubanize them.”
Now one shows a man groping a naked breast; another has two men.
During a condom giveaway for World AIDS Day, women laughed as volunteers — mostly gay men — dropped condoms into their cleavages.
“Just one?” one woman said. “What am I going to do with just one?”
Omairy Lorenzo, 18, a journalism student in Havana watching the giveaway, said she had been shown how to put a condom on a model penis at school when she was 12.
Her classmate Abel Lescaille, 20, said, “Sometimes they do so much sex education that you get tired of it.”
Until recently, Cuban society and government policies were deeply homophobic; in the revolution’s early days, gay men were sent to labor camps. Fidel Castro now publicly says he regrets that action.
Now there is more acceptance.
At the same time, the government controls virtually all real estate, and there are no gay bars or hotels. Cruising men often have unsafe sex in abandoned buildings or parks where muggers lurk and the police conduct raids, said Libán Molina, 41, a volunteer at an AIDS prevention hot line.
Only about half of the 11,674 Cubans living with H.I.V. are now on antiretroviral drugs.
In theory, Cuba would be an ideal laboratory for “test and treat,” the new protocol in which patients who test positive go on drugs immediately to reduce by 95 percent their chance of infecting anyone else.
However, it requires modern drugs and Cuba makes only the older, harsher ones. Only about 1,100 patients get new drugs, paid for by foreign donors.
“We know about test-and-treat,” Dr. Pérez said. “We would do it, if we could. But we need the funds.”

Sunday, May 6, 2012

778. Can Organic Food Feed the World? New Study Sheds Light On Debate Over Organic Vs. Conventional Agriculture


An organic food market

ScienceDaily, April 25, 2012  

Can organic agriculture feed the world? Although organic techniques may not be able to do the job alone, they do have an important role to play in feeding a growing global population while minimizing environmental damage, according to researchers at McGill University and the University of Minnesota.

A new study published in Nature concludes that crop yields from organic farming are generally lower than from conventional agriculture. That is particularly true for cereals, which are staples of the human diet -- yet the yield gap is much less significant for certain crops, and under certain growing conditions, according to the researchers.

The study, which represents a comprehensive analysis of the current scientific literature on organic-to-conventional yield comparisons, aims to shed light on the often heated debate over organic versus conventional farming. Some people point to conventional agriculture as a big environmental threat that undercuts biodiversity and water resources, while releasing greenhouse gases. Others argue that large-scale organic farming would take up more land and make food unaffordable for most of the world's poor and hungry.

"To achieve sustainable food security we will likely need many different techniques -- including organic, conventional, and possible 'hybrid' systems -- to produce more food at affordable prices, ensure livelihoods to farmers, and reduce the environmental costs of agriculture," the researchers conclude.

Overall, organic yields are 25% lower than conventional, the study finds. The difference varies widely across crop types and species, however. Yields of legumes and perennials (such as soybeans and fruits), for example, are much closer to those of conventional crops, according to the study, conducted by doctoral student Verena Seufert and Geography professor Navin Ramankutty of McGill and Prof. Jonathan Foley of the University of Minnesota's Institute on the Environment.

What's more, when best management practices are used for organic crops, overall yields are just 13% lower than conventional levels. "These results suggest that today's organic systems may nearly rival conventional yields in some cases -- with particular crop types, growing conditions and management practices -- but often they do not," the researchers write. Improvements in organic management techniques, or adoption of organic agriculture under environmental conditions where it performs best, may help close the yield gap, they indicate.

"Our study indicates that organically fertilized systems might require higher nitrogen inputs to achieve high yields as organic nitrogen is less readily available to crops. In some cases, organic farmers may therefore benefit by making limited use of chemical fertilizers instead of relying only on manure to supply nitrogen to their crops," Seufert says. "At the same time, conventional agriculture can learn from successful organic systems and implement practices that have shown environmental benefits, such as increased crop diversity and use of crop residues."

Yields are only part of a set of economic, social and environmental factors that should be considered when gauging the benefits of different farming systems, the researchers note. "Maybe people are asking the wrong question," Prof Ramankutty says. "Instead of asking if food is organically grown, maybe we should be asking if it's sustainably grown."
The results point to a need to get beyond the black-and-white, ideological debates that often pit advocates of organic and local foods against proponents of conventional agriculture, Prof. Foley adds. "By combining organic and conventional practices in a way that maximizes food production and social good while minimizing adverse environmental impact, we can create a truly sustainable food system."
Story Source:
The above story is reprinted from materials provided by McGill University, via Newswise.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Verena Seufert, Navin Ramankutty, Jonathan A. Foley.Comparing the yields of organic and conventional agriculture. Nature, 2012; DOI: 10.1038/nature1106

777. Almost Seven Million Birds Perish at Communication Towers in North America Each Year


Estimated annual avian mortality from communication towers by Bird
Conservation Region. High mortality estimates in Peninsular Florida
and Southeastern Coastal Plain reflect the more numerous and
taller communication towers in these regions.
(Credit: Longcore et al. PLoS One;
doi/10.1371/journal.pone.0034025.g006)
ScienceDaily, April 25, 2012   


Every year nearly 7 million birds die as they migrate from the United States and Canada to Central and South America, according to a new USC study published on April 25 in the journal PLoS ONE.

The birds are killed by the 84,000 communication towers that dot North America and can rise nearly 2,000 feet into the sky, according to the authors of "An Estimate of Avian Mortality at Communication Towers in the United States and Canada."

Placing that figure in context, the Exxon Valdez oil spill killed 250,000 birds and the Empire State building is 1,250 feet high.

"This is a tragedy that does not have to be," said lead author Travis Longcore, associate professor in the USC Spatial Sciences Institute at the USC Dornsife College of Letters, Arts and Sciences.

The taller the tower the greater the threat, the study found. The 1,000 or so towers above 900 feet accounted for only 1.6 percent of the total number of towers. Yet these skyscraper towers killed 70 percent of the birds, about 4.5 million a year, Longcore said.

Most of the birds spent winter in places like the Bahamas and summer in Canada. With names like the Common Yellowthroat and the Tennessee Warbler, they could fit in the palm of one's hand.

"These birds eat insects and keep our forests healthy," Longcore said. "They are quite beautiful. We have a long history of appreciating birds. Millions of people watch birds."

However, the birds are not generally killed by running into the tower itself but the dozens of cables, known as guy wires, that prop up the thin, freestanding structure, Longcore said.

During bad weather, the birds were pushed down by cloud cover and flew at lower altitudes. The clouds also removed navigation cues, such as stars, leaving only the blinking or static red lights of towers.

The blinking did not fool the birds, but towers with a static red light resulted in more dead birds.

"In the presence of the solid red lights, the birds are unable to get out of their spell," Longcore said. "They circle the tower and run into the big cables holding it up."

Longcore estimated that changing the steady-burning lights on the 4,500 towers greater than 490 feet tall (about 6 percent of the total) could reduce mortality about 45 percent, or about 2.5 million birds. The study also recommended that businesses share towers to reduce their number and build more freestanding towers to reduce the need for guy wires.

In 2005, Longcore and his colleagues started collecting and analyzing data from field studies that counted the number of bird kills at communication towers across the United States. The team only used findings that documented bird kills for at least a year and in some cases for several decades.

The numbers were scrutinized to find the average bird mortality based on height, the guy wires and the types of lights affixed to the tower.

The team then matched up tower types, sizes and attributes of 38 tower studies, applying those findings to the 84,000 towers across Canada and the United States in preparation for the new publication, which also was submitted to the Federal Communications Commission.

"One of the things this country has been great about is saying we care about not losing species on our watch," Longcore said. "With these towers, we are killing birds in an unnatural way. This is senseless."

The study, which does not include shorter towers that typically are used for mobile telephone transmission, focused on towers taller than 180 feet, which typically provide TV and radio frequencies.

The study's authors included Catherine Rich and Beau MacDonald of The Urban Wildlands Group, Pierre Mineau, Daniel G. Bert and Erin Mutrie of Environment Canada, Lauren M. Sullivan of UCLA, Sidney A. Gauthreaux of Clemson University, Michael Avery of the U.S. Department of Agriculture/Wildlife Services, Albert M. Manville of U.S. Fish and Wildlife Service, Emilie Travis and David Drake of the University of Wisconsin and independent scholar Robert L. Crawford.

The study was funded in part by The Urban Wildlands Group, Environment Canada, the American Bird Conservancy and Defenders of Wildlife.


Story Source:
The above story is reprinted from materials provided by University of Southern California. The original article was written by Eddie North-Hager.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Longcore T, Rich C, Mineau P, MacDonald B, Bert DG, et al. An Estimate of Avian Mortality at Communication Towers in the United States and Canada. PLoS ONE, 2012; 7(4): e34025 DOI: 10.1371/journal.pone.0034025

776. The Environmental Cost of China's Economic Growth


A Chinese industrial park

ScienceDaily, April 27, 2012 

China's economic growth will continue to be energy-intensive and highly polluting for the foreseeable future with emissions and efficiency far below capital growth on the agenda, according to a study published in the International Journal of Global Energy Issues.

Economist Yanqing Xia of Dongbei University of Finance and Economics and the Northeast Branch of the Chinese Academy of Sciences in Liaoning has looked at almost a decade's worth of data from 30 Chinese provinces to build a comprehensive model of pollution, energy consumption and economic growth. The model offers an empirical look at the balance between economic growth, energy consumption and pollution and gives a positive outlook for average gross domestic product (GDP) but paints a rather bleak medium-term view regarding a lack of sustainability and environmental targets.

Economic growth in China is heavily invested in the development of manufacturing and heavy industries, export and fixed asset investment, and energy consumption is thus growing rapidly. In one sense, energy consumption underlies economic growth. Unfortunately, this rapid increase in energy consumption and the rise in pollution and carbon emissions reflects rapid economic growth but is adding to environmental harm on a global scale and having a tremendous impact on ecological systems.

Xia points out that the data show that energy consumption has a greater impact on output compared with conventional factors of production such as labor (human capital), while pollution has relatively little effect on output. "China's economic growth is still powered by physical capital expansion and substantial energy consumption, she says. Energy consumption and pollution still increase with China's economic growth.

China is a rapidly developing nation but Xia suggests that economic growth and environmental protection must now be bound together. "China must implement effective environmental regulations so that firms and consumers can be properly encouraged to reduce pollution and energy consumption," she asserts. Economic growth may continue unhindered for many years in China but the environmental payback may stymie opportunities to reap the rewards of that growth because of the harm that ignoring environmental urgency may cause.

Story Source:
The above story is reprinted from materials provided by Inderscience Publishers, via EurekAlert!, a service of AAAS.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Yanqing Xia. An empirical research on the interactions of China's energy consumption, pollution emissions and economic growth. International Journal of Global Energy Issues, 2012, 35, 411-425

775. Evolutionary Theory: Darwinian Selection Continues to Influence Human Evolution


ScienceDaily, April 30, 2012 
A Finnish family featured in the research.
(Credit: Image courtesy of University of Sheffield)

New evidence proves humans are continuing to evolve and that significant natural and sexual selection is still taking place in our species in the modern world.

Despite advancements in medicine and technology, as well as an increased prevalence of monogamy, research reveals humans are continuing to evolve just like other species.

Scientists in an international collaboration, which includes the University of Sheffield, analysed church records of about 6,000 Finnish people born between 1760-1849 to determine whether the demographic, cultural and technological changes of the agricultural revolution affected natural and sexual selection in our species.

Project leader Dr Virpi Lummaa, of the University's Department of Animal and Plant Sciences, said: "We have shown advances have not challenged the fact that our species is still evolving, just like all the other species 'in the wild'. It is a common misunderstanding that evolution took place a long time ago, and that to understand ourselves we must look back to the hunter-gatherer days of humans."
Dr Lummaa added: "We have shown significant selection has been taking place in very recent populations, and likely still occurs, so humans continue to be affected by both natural and sexual selection. Although the specific pressures, the factors making some individuals able to survive better, or have better success at finding partners and produce more kids, have changed across time and differ in different populations."

As for most animal species, the authors found that men and women are not equal concerning Darwinian selection.

Principal investigator Dr Alexandre Courtiol, of the Wissenschftskolleg zu Berlin, added: "Characteristics increasing the mating success of men are likely to evolve faster than those increasing the mating success of women. This is because mating with more partners was shown to increase reproductive success more in men than in women. Surprisingly, however, selection affected wealthy and poor people in the society to the same extent."

The experts needed detailed information on large numbers of study subjects to be able to study selection over the entire life cycle of individuals: survival to adulthood, mate access, mating success, and fertility per mate.

Genealogy is very popular in Finland and the country has some of the best available data for such research thanks to detailed church records of births, deaths, marriages and wealth status which were kept for tax purposes. Movement in the country was also very limited until the 20th century.

"Studying evolution requires large sample sizes with individual-based data covering the entire lifespan of each born person," said Dr Lummaa. "We need unbiased datasets that report the life events for everyone born. Because natural and sexual selection acts differently on different classes of individuals and across the life cycle, we needed to study selection with respect to these characteristics in order to understand how our species evolves."

The project was funded by the European Research Council and the Kone Foundation (Finland) and was carried out with Wissenschftskolleg zu Berlin and the Leibniz Institute for Zoo and Wildlife Research in Germany, University of Turku in Finland, University of Helsinki in Finland, and the Population Research Institute in Finland.

Story Source:
The above story is reprinted from materials provided by University of Sheffield.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Alexandre Courtiol, Jenni E. Pettay, Markus Jokela, Anna Rotkirch, and Virpi Lummaa. Natural and sexual selection in a monogamous historical human population. PNAS, April 30, 2012 DOI: 10.1073/pnas.1118174109


774. Humans Discover that Rats Recall the Past to Make Daily Decisions


 ScienceDaily, May 3, 2012

Brain patterns through which the rats see rapid replays
 of past experiences are fundamental to their ability
 to make decisions. Disturbing those particular brain patterns
 impaired the animals' ability to learn rules based on memories
 of things that had happened in the past.
(Credit: © Oleg Kozlov / Fotolia)
UCSF scientists have identified patterns of brain activity in the rat brain that play a role in the formation and recall of memories and decision-making. The discovery, which builds on the team's previous findings, offers a path for studying learning, decision-making and post-traumatic stress syndrome.

The researchers previously identified patterns of brain activity in the rat hippocampus, a brain region critical for memory storage. The patterns sometimes represented where an animal was in space, and, at other times, represented fast-motion replays of places the animal had been, but no one knew whether these patterns indicated the process of memory formation and recollection.

In the journal Science this week (online May 3, 2012), the UCSF researchers demonstrated that the brain activity is critical for memory formation and recall. Moreover, they showed that the brain patterns through which the rats see rapid replays of past experiences are fundamental to their ability to make decisions. Disturbing those particular brain patterns impaired the animals' ability to learn rules based on memories of things that had happened in the past.

"We think these memory-replay events are central to understanding how the brain retrieves past experiences and uses them to make decisions," said neuroscientist Loren Frank, PhD, a associate professor of physiology and a member of the Keck Center for Integrative Neuroscience at UCSF, who led the research with Shantanu Jadhav, PhD, a post-doctoral fellow. "They offer insight into how a past experience can have such a profound effect on how we think and feel."

The finding gives scientists a new way to investigate fundamental processes like learning and decision-making in animals and in people. It also may help shed light on memory disorders like post-traumatic stress disorder (PTSD), which is characterized by strong, disturbing and uncontrolled memories.

Without Links to the Past, Rats Face Indecision
Seeking to understand how the recall of specific memories in the brain guides our thinking, Frank and his colleagues built a system for detecting the underlying patterns of neuronal activity in rats. They fitted the animals with electrodes and built a system that enabled them to detect a specific pattern, called a sharp-wave ripple, in the hippocampus. Whenever they detected a ripple, they would send a small amount of electricity into another set of electrodes that would immediately interrupt the ripple event, in effect turning off all memory replay activity without otherwise affecting the brain.

The UCSF researchers knew that these sharp-wave ripples would be activated when the animals had to make choices about which direction to turn as they wended their way toward their reward: a few drops of sweetened condensed milk. These signals seem to be flashes of memory recall, said Frank, a rat's past knowledge flooding back to inform it on what had happened in the past and where it might go in the future. Squashing the sharp-wave ripples, the UCSF team found, disrupted the recall and subverted the rat's ability to correctly navigate the maze.

This shows, said Frank, that the sharp-wave ripples are critical for this type of memory recall. Through these brain waves, the rat reprocesses and replays old experiences in a fleeting instant -- lessons from the past essential for shaping their perception of the present.

"We think these memory replay events are a fundamental constituent of memory retrieval and play a key role in human perspective and decision-making as well," he said. "These same events have been seen in memory tasks in humans, and now we know they are critical for memory in rats. We think that these fast-forward replays make up the individual elements of our own memories, which jump rapidly from event to event."

Next, the team wants to tease out information about how the rats actually use these memory replay events to make decisions and how amplifying or blocking specific replay events will change the way an animal learns and remembers. They also think that these events could be important for understanding memory problems, as when stressful memories intrude into daily life.

Story Source:
The above story is reprinted from materials provided by University of California, San Francisco (UCSF), viaNewswise. The original article was written by Jason Bardi.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Shantanu P. Jadhav, Caleb Kemere, P. Walter German and Loren M. Frank. Awake Hippocampal Sharp-Wave Ripples Support Spatial Memory. Science, May 4, 2012 DOI: 10.1126/science.1217230