Green tea is said to have many putative positive effects on health.
Now, researchers at the University of Basel are reporting first evidence that green tea extract enhances the cognitive functions, in particular the working memory. The Swiss findings suggest promising clinical implications for the treatment of cognitive impairments in psychiatric disorders such as dementia. The academic journalPsychopharmacology has published their results.
In the past the main ingredients of green tea have been thoroughly studied in cancer research. Recently, scientists have also been inquiring into the beverage’s positive impact on the human brain. Different studies were able to link green tea to beneficial effects on the cognitive performance. However, the neural mechanisms underlying this cognitive enhancing effect of green tea remained unknown.
In a new study, the researcher teams of Prof. Christoph Beglinger from the University Hospital of Basel and Prof. Stefan Borgwardt from the Psychiatric University Clinics found that green tea extract increases the brain’s effective connectivity, meaning the causal influence that one brain area exerts over another. This effect on connectivity also led to improvement in actual cognitive performance: Subjects tested significantly better for working memory tasks after the admission of green tea extract.
For the study healthy male volunteers received a soft drink containing several grams of green tea extract before they solved working memory tasks. The scientists then analyzed how this affected the brain activity of the men using magnetic resonance imaging (MRI). The MRI showed increased connectivity between the parietal and the frontal cortex of the brain. These neuronal findings correlated positively with improvement in task performance of the participants. «Our findings suggest that green tea might increase the short-term synaptic plasticity of the brain», says Borgwardt.
The research results suggest promising clinical implications: Modeling effective connectivity among frontal and parietal brain regions during working memory processing might help to assess the efficacy of green tea for the treatment of cognitive impairments in neuropsychiatric disorders such as dementia.
When individuals engage in risky business transactions with each other, they may end up being disappointed.
This is why they’d rather leave the decision on how to divvy up jointly-owned monies to a computer than to their business partner. This subconscious strategy seems to help them avoid the negative emotions associated with any breaches of trust. This is the result of a study by scientists from the University of Bonn and US peers. They are presenting their findings in the scientific journal “Proceedings of the Royal Society B.”
Trust is an essential basis for business relationships. However, this basis can be shaken if one business partner exhibits dishonest behavior. “Everyone knows that trust can be shattered in risky businesses,” explained Prof. Dr. Bernd Weber from the Center for Economics and Neuroscience (CENs) at the University of Bonn. “As a result, people are not all that eager to put their trust in others.” Scientists call this attitude “betrayal aversion” – people try to avoid being disappointed by potential breaches of trust.
In a current study, Prof. Weber and his US colleagues, Prof. Dr. Jason A. Aimone from Baylor University and Prof. Dr. Daniel Houser from George Mason University examined in experiments the effects betrayal aversion has on simple financial decisions. A total of 30 subjects played a computer game at George Mason University in Arlington, VA (USA) that promised real monies to the winners. At the Life & Brain Zentrum of the University of Bonn, the same number of subjects then made their decisions based on the results of the earlier experiment. And while the Bonn subjects were responding to their gaming partners’ decisions made earlier in Arlington, their brain activity was measured by means of MRI scans.
Sharing fairly or making a profit at the other person’s expense?
In this experiment, the test subjects in Bonn were able to select whether they and their US partners would get one euro each only, or whether they wanted to have a higher amount – i.e., 6 euros – divided up. However, the latter variant came with a risk. So, for example, the other player might get as much as 5.60 euros while the Bonn player would be left with only 40 Cents. The actual dividing of the amount, which came in a second step, could be left either to one’s partner or to the computer. However, the computer gave out exactly the same decisions as the real test subjects. “So, from the point of view of winnings, there was no difference whether the other player or the machine divided the amount,” explained Prof. Weber. “And the subjects had explicitly been told so from the very start.”
Even though the winnings were exactly the same in the end, more subjects put their trust into the computer. When the money was divided by the computer, 63 percent of subjects trusted the process and only 37 percent preferred taking just the one euro. But if the arrangement was that the human partners would make the decision, only 49 percent of test subjects trusted them – 51 percent would rather take the more secure, small amount. “These results show that more subjects prefer to leave risky decisions in which they may be betrayed to an impersonal device, thus avoiding the negative feeling that comes from having wrongly trusted a human,” said Prof. Weber, adding that obviously a breach of trust committed by an impersonal computer was less emotionally stressful than if had been a private business partner.
The brain’s frontal insula was especially active
The University of Bonn’s subjects also showed interesting brain activities as measured in MRI scans. In the process of making financial decisions, the frontal insula was especially active when it was another player who made the decision on how to divide the amount. “This area of the brain is always involved when negative emotions such as pain, disappointment or fear are activated,” explained Prof. Weber. He added that the fact that the frontal insula was activated is a clear indication that negative emotions played an important role in these situations.
Financial decisions are very complex. “This is a very contrary phenomenon. Many studies show that the anonymity of business partners on the Internet results in a loss of trust,” said Prof. Weber. “But our results indicate that this anonymity can also help avoid negative feelings.” He added that these decision processes in financial transactions would yet have to be studied in more detail.
Research that could lead to new medical imaging methods and better treatments for stroke and other brain conditions
A technique Stanford Linear Accelerator Center (SLAC) scientists invented for scanning ancient manuscripts is now being used to probe the human brain, in research that could lead to new medical imaging methods and better treatments for stroke and other brain conditions.
The studies, taking place at SLAC’s Stanford Synchrotron Radiation Lightsource, are led by cell biologist Helen Nichol, of the University of Saskatchewan, with $2.5 million in funding from the Canadian government and the Heart and Stroke Foundation of Canada.
Her team, which includes a Stanford neurosurgeon and stem cell expert, other medical doctors and experts in stroke research and medical imaging, reflects the broad ambitions of this research: to give doctors a better understanding of what they’re seeing in MRI scans of stroke patients; to improve diagnosis and guide treatments; and maybe even to develop new ways to peer inside the living brain. What all these goals have in common is that they depend on the ability to track movements and deposits of tiny traces of metal in human tissue. That’s a job the SSRL technique, known as rapid-scanning XRF, is exquisitely suited to do.
At a synchrotron equipped with this technology, “you can see a large sample of brain, and you have the high resolution the technique offers to actually zoom in on your single cells,” said Dr. Raphael Guzman, a pediatric neurosurgeon and stem cell expert at Stanford University Medical Center who is leading part of the study.
Regular XRF, or X-ray fluorescence imaging, uses the SSRL’s powerful X-ray beam to knock electrons out of the inner shells of atoms in a sample. As more electrons fall in to fill the gaps, they give off light—fluoresce—and the color of that light reveals which chemical elements are present.
In the mid-2000s, SLAC scientists had a chance to use this technique to examine a priceless manuscript—the Archimedes palimpsest, a 10th century parchment containing copies of works by the ancient Greek mathematician that had been erased by monks and recycled as a prayer book. But they soon realized that to examine something this big in a reasonable amount of time, they would have to make the scanning go much faster.
Led by physicist Uwe Bergmann, they developed a way to move the beam continually over the sample, rather than imaging one spot at a time. This allowed them to proceed 300 times faster—a scan that used to take 12 days could now be done in an hour—and opened up the possibility of examining much bigger samples, from art objects and cultural artifacts to fossils of early birds. In 2006, Bergmann and an international team of researchers used rapid-scanning XRF to reveal the words of Archimedes, including passages that had been lost for centuries, beneath the prayer writings on the old parchment.
When she read about this research, Nichol said, “It just grabbed me. I thought, if he could map something as big as a sheet of paper, we could map a brain.”
She and her colleagues began using rapid-scanning XRF at the SSRL to look at metals in the preserved brains of people who had died with Alzheimer’s disease, Parkinson’s disease or multiple sclerosis. The healthy brain needs metals like iron, zinc, manganese and copper to work properly, and some studies had indicated that in people with neurodegenerative diseases, the normal distribution of these metals was out of whack. But did these changes cause the disease, or were they a result of it? And were they consistent enough to offer a tool for diagnosis?
To the team’s disappointment, scans of brain slices from eight people with Parkinson’s disease found no clear pattern—nothing that could help doctors diagnose their brain conditions or understand how they came about. “What we found is that the changes you see in Parkinson’s and Alzheimer’s are sort of variations on normal,” Nichol said.
She decided that beam time on the SSRL was better spent studying a disorder that caused clear, obvious damage in the brain. Stroke fit the bill.
When a stroke blocks the flow of blood to the brain, it produces striking lesions, almost like bruises, caused by bleeding and tissue death. Blood contains iron, which is part of the hemoglobin that carries oxygen in red blood cells. When bleeding occurs, the iron leaks out in a form that can damage surrounding cells, so the body quickly tucks the iron away in various chemical compounds for safe storage.
Standard MRI scans can image and identify those iron compounds and show doctors where bleeding has taken place. But they may not catch the very smallest bleeds, Nichol said, or identify other elements that may be disrupted during a stroke.
That’s where RS-XRF comes in. As the first practical tool for imaging a number of different metals in all of their chemical forms at the same time—and over a large section of the brain—it “opens up a lot of doors to things you can’t see with medical imaging,” Nichol said. It also can tell one form of iron from another; the spectrum of iron in hemoglobin will look different than free-floating iron or the iron compounds produced by bleeding, for instance.
The idea behind the study is that iron in its varied forms can be used as a marker to reveal changes in molecules and cells that follow a stroke, evaluate stroke damage and follow the migration of stem cells that are injected into patients in experimental stroke treatments. The scientists will also look at sulfur compounds that are thought to play a role in protecting the brain from damage, and evaluate the effects of the few stroke treatments available, such as chilling the brain, on the distribution of iron and sulfur.
Members of the team come to the SSRL about three weeks per year to scan brain tissue from rats, including some that have been bred to make them unusually susceptible to stroke, as well as human brain tissue from the National Institutes of Health brain bank. Additional experiments are being done at the Canadian Light Source at the University of Saskatchewan.
While they are not putting live patients in a synchrotron, the scientists hope their findings will someday result in the ability to scan live patients with methods that are much more sensitive to damage from tiny strokes that now go unnoticed.