Monday, September 21, 2009

MEMORIES EXIST EVEN WHEN FORGOTTEN

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A woman looks familiar, but you can't remember her name or where you met her. New research by UC Irvine neuroscientists suggests the memory exists – you simply can't retrieve it.

Using advanced brain imaging techniques, the scientists discovered that a person's brain activity while remembering an event is very similar to when it was first experienced, even if specifics can't be recalled.

"If the details are still there, hopefully we can find a way to access them," said Jeff Johnson, postdoctoral researcher at UCI's Center for the Neurobiology of Learning & Memory and lead author of the study, appearing Sept. 10 in the journal Neuron.

"By understanding how this works in young, healthy adults, we can potentially gain insight into situations where our memories fail more noticeably, such as when we get older," he said. "It also might shed light on the fate of vivid memories of traumatic events that we may want to forget."

In collaboration with scientists at Princeton University, Johnson and colleague Michael Rugg, CNLM director, used functional magnetic resonance imaging to study the brain activity of students.

Inside an fMRI scanner, the students were shown words and asked to perform various tasks: imagine how an artist would draw the object named by the word, think about how the object is used, or pronounce the word backward in their minds. The scanner captured images of their brain activity during these exercises.

About 20 minutes later, the students viewed the words a second time and were asked to remember any details linked to them. Again, brain activity was recorded.

Utilizing a mathematical method called pattern analysis, the scientists associated the different tasks with distinct patterns of brain activity. When a student had a strong recollection of a word from a particular task, the pattern was very similar to the one generated during the task. When recollection was weak or nonexistent, the pattern was not as prominent but still recognizable as belonging to that particular task.

"The pattern analyzer could accurately identify tasks based on the patterns generated, regardless of whether the subject remembered specific details," Johnson said. "This tells us the brain knew something about what had occurred, even though the subject was not aware of the information."

(Photo: Daniel A. Anderson / University Communications)

UC Irvine

MORE OXYGEN - COLDER CLIMATE

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Outer space offers a new perspective for measuring economic growth, according to new research by three Brown University economists. In a National Bureau of Economic Research working paper, J. Vernon Henderson, Adam Storeygard, and David N. Weil suggest a new framework for estimating a country or region’s gross domestic product (GDP) by using satellite images of the area’s nighttime lights.

Using a completely new method, researchers have shown that high atmospheric and oceanic oxygen content makes the climate colder. In prehistoric times, the earth experienced two periods of large increases and fluctuations in the oxygen level of the atmosphere and oceans. These fluctuations also lead to an explosion of multicellular organisms in the oceans, which are the predecessors for life as we know it today. The results are now being published in Nature.

Everybody talks about CO2 and other greenhouse gases as causes of global warming and the large climate changes we are currently experiencing. But what about the atmospheric and oceanic oxygen content? Which role does oxygen content play in global warming?

This question has become extremely relevant now that Professor Robert Frei from the Department of Geography and Geology at the University of Copenhagen, in collaboration with colleagues from Departamento de Geología, Facultad de Ciencias in Uruguay, Newcastle University and the University of Southern Denmark, has established that there is a historical correlation between oxygen and temperature fluctuations towards global cooling.

The team of researchers reached their conclusions via analyses of iron-rich stones, so called banded iron formations, from different locations around the globe and covering a time span of more than 3,000 million years. Their discovery was made possible by a new analytical method which the research team developed. This method is based on analysis of chrome isotopes – different chemical variants of the element chrome. It turned out that the chrome isotopes in the iron rich stones reflect the oxygen content of the atmosphere. The method is a unique tool, which makes it possible to examine historical changes in the atmospheric oxygen content and thereby possible climate changes.

“But we can simply conclude that high oxygen content in seawater enables a lot of life in the oceans “consuming” the greenhouse gas CO2, and which subsequently leads to a cooling of the earth’s surface. Throughout history our climate has been dependent on balance between CO2 and atmospheric oxygen. The more CO2 and other greenhouse gases, the warmer the climate has been. But we still don’t know much about the process which drives the earth from a period with a warmer climate towards an “ice age” with colder temperatures – other than that oxygen content plays an important role. It would therefore be interesting to consider atmospheric and oceanic oxygen contents much more in research aiming at understanding and tackling the causes of the current climate change,” says Professor Robert Frei.

The results Professor Frei and his international research team have obtained indicate that there have been two periods in the earth’s 4.5 billion year history where a significant change in the atmospheric and oceanic oxygen content has occurred. The first large increase took place in between 2.45 billion years and 2.2 billion years ago. The second “boost” occurred for only 800 to 542 million years ago and lead to an oxidisation of the deep oceans and thereby the possibility for life to exist at those depths.

”To understand the future, we have to understand the past. The two large increases in the oxygen content show, at the very least, that the temperature decreased. We hope that these results can contribute to our understanding of the complexity of climate change. I don’t believe that humans have a lot of influence on the major process of oxygen formation on a large scale or on the inevitable ice ages or variations in temperature that the Earth’s history is full of. But that doesn’t mean that we cannot do anything to slow down the current global warming trend. For example by increased forestry and other initiatives that help to increase atmospheric and oceanic oxygen levels,” explains Professor Robert Frei, who, along with his research team, has worked on the project for three years so far.

University of Copenhagen

YOU CAN BELIEVE YOUR EYES: NEW INSIGHTS INTO MEMORY WITHOUT CONSCIOUS AWARENESS

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The hippocampus is a brain region that is critical for conscious recollection of past events but the precise role of this area in memory remains controversial. According to one theory, even if explicit retrieval fails, the hippocampus might still support expressions of relational memory (e.g., memory for the co-occurrence of items in the context of some scene or event) when sensitive, indirect testing methods are used.

To test this theory, Drs. Deborah Hannula and Charan Ranganath, both from the Center for Neuroscience at the University of California, Davis, used functional magnetic resonance imaging to examine participants' brain activity while they attempted to remember previously studied face-scene pairings. During scanning, participants were shown a previously studied scene along with three previously studied faces and were asked to identify the face that had been paired with that scene earlier. Eye movements were also monitored during the task and provided an indirect measure of memory.

During each test trial, participants frequently spent more time viewing the face that had been previously paired with the scene—an eye-movement-based memory effect. What is more surprising is that hippocampal activity was closely tied to participants' tendency to view the associated face, even when they failed to identify it. Activity in the prefrontal cortex, an area required for decision making, was sensitive to whether or not participants had responded correctly and communication between the prefrontal cortex and the hippocampus was increased during correct, but not incorrect, trials.

The findings may shed light on the role of the hippocampus in memory and awareness, as they suggest that even when people fail to recollect a past event, the hippocampus might still support an expression of memory through eye movements. Furthermore, the results suggest that even when the hippocampus is doing its job, conscious memory may depend on interactions between the hippocampus and the prefrontal cortex.

One implication of the results is that eye movements might be used to indirectly assess memory and hippocampal function in cognitively impaired patients, children, or others who might have difficulty with conventional memory tests. More intriguing is the possibility that these measures might also track memory in uncooperative individuals. "It is conceivable that eye-tracking could be used to obtain information about past events from participants who are unaware or attempting to withhold information," offers Dr. Hannula. "In other words, there may be circumstances in which eye movements provide a more robust account of past events or experiences than behavioral reports alone."

Cell Press

MACHINES CAN'T REPLICATE HUMAN IMAGE RECOGNITION, YET

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While computers can replicate many aspects of human behavior, they do not possess our ability to recognize distorted images, according to a team of Penn State researchers.

"Our goal is to seek a better understanding of the fundamental differences between humans and machines and utilize this in developing automated methods for distinguishing humans and robotic programs," said James Z. Wang, associate professor in Penn State's College of Information Sciences and Technology.

Wang, along with Ritendra Datta, a Penn State Ph.D. recipient, and Jia Li, associate professor of statistics at Penn State, explored the difference in human and machine recognition of visual concepts under various image distortions.

The researchers used those differences to design image-based CAPTCHAs (Completely Automated Public Turing Test to Tell Computers and Humans Apart), visual devices used to prevent automated network attacks.

Many e-commerce web sites use CAPTCHAs, which are randomly generated sets of words that a user types in a box provided in order to complete a registration or purchasing process. This is done to verify that the user is human and not a robotic program.

In Wang's study, a demonstration program with an image-based CAPTCHA called IMAGINATION was presented on imagination.alipr.com. Both humans and robotic programs were observed using the CAPTCHA.

Although the scope of the human users was limited, the results, presented in the September issue of IEEE Transactions on Information Forensics and Security, proved that robotic programs were not able to recognize distorted images. In other words, a computer recognition program had to rely on an accurate picture, while humans were able to tell what the picture was even though it was distorted.

Wang said he hopes to work with developers in the future to make IMAGINATION a CAPTCHA program that Web sites can use to strengthen the prevention of automated network attacks.

Even though machine recognizability does not exceed human recognizability at this time, Wang says that there is a possibility that it will in the future.

"We are seeing more intelligently designed computer programs that can harness a large volume of online data, much more than a typical human can experience in a lifetime, for knowledge generation and automatic recognition," said Wang. "If certain obstacles, which many believe to be insurmountable, such as scalability and image representation, can be overcome, it is possible that one day machine recognizability can reach that of humans."

The Pennsylvania State University

BABY BOOMERS' BOON? LED LIGHT AND GREEN TEA CREAM TO SMOOTH FACIAL WRINKLES

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Scientists in Germany are reporting a major improvement in their potential new treatment for facial wrinkles that could emerge as an alternative to Botox and cosmetic surgery. The non-invasive technique combines high-intensity light from light-emitting diodes (LEDs) and a lotion made of green tea extract. It works ten times faster than a similar anti-wrinkle treatment that uses LEDs alone, the researchers say. Their study is scheduled for the Oct. 7 issue of ACS' Crystal Growth & Design, a bi-monthly journal.

Andrei P. Sommer and Dan Zhu point out that researchers have used light-therapy, or phototherapy, for more than 40 years to help heal wounds. Recently the scientists showed that use of high-intensity LEDs, similar to those used in automotive tail lights and computers, could help reduce skin wrinkles when applied daily for several months. But exposure to intense LED light is also involved in generating high levels of reactive oxygen species as byproducts that can potentially damage cells. To combat that effect, the researchers combined the LED with a potent antioxidant in green tea extract called epigallocatechin gallate.

They applied a daily combination of LED light and green tea extract to the facial wrinkles of a human volunteer one month. The combination treatment resulted in smoother skin, including "less pronounced wrinkle levels, shorter wrinkle valleys, and juvenile complexion," the scientists say. The treatment showed promising results in only one-tenth of the time it took for LED therapy alone to reduce wrinkles. The study could form the basis of "an effective facial rejuvenation program," and lead to a new understanding of the effect reactive oxygen species on cellular aging, they note.

(Photo: Crystal Growth & Design)

American Chemical Society

NEW RESEARCH CONFIRMS POTENTIAL DEADLY NATURE OF EMERGING NEW MONKEY MALARIA SPECIES IN HUMANS

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Researchers in Malaysia have identified key laboratory and clinical features of an emerging new form of malaria infection. The research, funded by the Wellcome Trust, confirms the potentially deadly nature of the disease.

Malaria kills more than a million people each year. It is caused by malaria parasites, which are injected into the bloodstream by infected mosquitoes. Of the four species of malaria that commonly cause disease in humans, Plasmodium falciparum, found most commonly in Africa, is the most deadly. P. malariae, found in tropical and sub-tropical regions across the globe, has symptoms that are usually less serious.

Recently, researchers at the University Malaysia Sarawak, led by Professors Balbir Singh and Janet Cox-Singh, showed that P. knowlesi, a malaria parasite previously thought to mainly infect only monkeys – in particular long-tailed and pig-tailed macaques found in the rainforests of Southeast Asia – was widespread amongst humans in Malaysia. Subsequent reports in neighbouring Southeast Asian countries have led to the recognition of P. knowlesi as the fifth cause of malaria in humans.

Now, in a study published in the journal Clinical Infectious Diseases, Professors Singh and Cox-Singh, together with colleagues from University Malaysia Sarawak, Kapit Hospital and the University of Western Australia, have published the first detailed prospective study of the clinical and laboratory features of human P. knowlesi infections.

"P. knowlesi malaria can easily be confused with P. malariae since these two parasites look similar by microscopy, but the latter causes a benign form of malaria," says Professor Singh. "In fact, because the P. knowlesi parasites reproduce every twenty four hours in the blood, the disease can be potentially fatal, so early diagnosis and appropriate treatment is essential. Understanding the most common features of the disease will be important in helping make this diagnosis and in planning appropriate clinical management."

The researchers initially recruited over 150 patients admitted to Kapit Hospital in Sarawak, Malaysian Borneo, between July 2006 and January 2008 who had tested positive with a blood film slide for Plasmodium species. Using molecular detection methods, P. knowlesi was found to be by far the most common infection amongst these patients, accounting for over two-thirds of all cases.

As with other types of malaria in humans, P. knowlesi infections resulted in a wide spectrum of disease. Most cases of infection were uncomplicated and easily treated with chloroquine and primaquine, two commonly used anti-malarial drugs. However, around one in ten patients had developed complications and two died. Complications included breathing difficulties and kidney problems (including kidney failure in a small number of cases), which are also common in severe P. falciparum cases. Although the researchers saw a case fatality rate of just under 2%, which makes P. knowlesi malaria as deadly as P. falciparum malaria, they stress that an accurate fatality rate is hard to determine given the relatively small number of cases studied so far.

All of the P. knowlesi patients – including those with uncomplicated malaria – had a low blood platelet count. In other human forms of malaria, this would only be expected in less than eight out of ten cases. In addition, the P. knowlesi platelet counts tended to be significantly lower than for other malarias. However, even though blood platelets are essential for blood clotting, no cases of excessive bleeding or problems with clotting were identified. The researchers believe the low blood platelet count could be used as a potential feature for diagnosis of P. knowlesi infections.

Recently, there have been cases of European travellers to Malaysia and an American traveller to the Philippines being admitted into hospital with knowlesi malaria following their return home.

"The increase in tourism in Southeast Asia may mean that more cases are detected in the future, including in Western countries," says Professor Singh. "Clinicians assessing a patient who has visited an area with known or possible P. knowlesi transmission should be aware of the diagnosis, clinical manifestations, and rapid and potentially serious course of P. knowlesi malaria."

(Photo: Andy Lawson on Flickr)

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