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【计时一】
Empathy Represses Analytic Thought, and Vice Versa: Brain Physiology Limits Simultaneous Use of Both Networks
ScienceDaily (Oct. 30, 2012) — New research shows a simple reason why even the most intelligent, complex brains can be taken by a swindler's story -- one that upon a second look offers clues it was false. [attachimg=300,449]109182[/attachimg]
When the brain fires up the network of neurons that allows us to empathize, it suppresses the network used for analysis, a pivotal study led by a Case Western Reserve University researcher shows. How could a CEO be so blind to the public relations fiasco his cost-cutting decision has made? When the analytic network is engaged, our ability to appreciate the human cost of our action is repressed. At rest, our brains cycle between the social and analytical networks. But when presented with a task, healthy adults engage the appropriate neural pathway, the researchers found. The study shows for the first time that we have a built-in neural constraint on our ability to be both empathetic and analytic at the same time The work suggests that established theories about two competing networks within the brain must be revised. More, it provides insights into the operation of a healthy mind versus those of the mentally ill or developmentally disabled. "This is the cognitive structure we've evolved," said Anthony Jack, an assistant professor of cognitive science at Case Western Reserve and lead author of the new study. "Empathetic and analytic thinking are, at least to some extent, mutually exclusive in the brain." The research is published in the current online issue of NeuroImage. A number of earlier studies showed that two large scale brain networks are in tension in the brain, one which is known as the default mode network and a second known as the task positive network. But other researchers have suggested that different mechanisms drive this tension: One theory says that we have one network for engaging in goal directed tasks. This theory posits that our second network allows the mind to wander. The other theory says that one network is for external attention, and the second network is for internal attention. The new study shows that adults presented with social or analytical problems -- all external stimuli -- consistently engaged the appropriate neural pathway to solve the problem, while repressing the other pathway. The see-sawing brain activity was recorded using functional magnetic resonance imaging. 【397】
【计时二】
Jack worked with former Case Western Reserve undergraduates Abigail Dawson, now a graduate student at the University of Otago in Dunedin, New Zealand; Katelyn Begany, now a graduate student at the University of California, Berkeley; and Kevin P. Barry, now a graduate student at Rensselaer Polytechnic Institute. Other co-authors are, from Case Western Reserve: former research assistant, Regina L. Leckie and Angela H. Ciccia, an assistant professor of psychological sciences; and Abraham Z. Snyder, MD, a professor of radiology at Washington University in St. Louis. Jack said that a philosophical question inspired the study design: "The most persistent question in the philosophy of mind is the problem of consciousness. Why can we describe the workings of a brain, but that doesn't tell us what it's like to be that person?" "The disconnect between experiential understanding and scientific understanding is known as the explanatory gap," Jack said. "In 2006, the philosopher Philip Robbins and I got together and we came up with a pretty crazy, bold hypothesis: that the explanatory gap is driven by our neural structure. I was genuinely surprised to see how powerfully these findings fit that theory." Philip Robbins is an associate professor of philosophy at the University of Missouri. These findings suggest the same neural phenomenon drives the explanatory gap as occurs when we look at a visual illusion such as the duck-rabbit, he continued. The drawing of the head of the animal can be seen as a duck facing one direction or a rabbit facing the other, but you can't see both at once. "That is called perceptual rivalry, and it occurs because of neural inhibition between the two representations," Jack said. "What we see in this study is similar, but much more wide-scale. We see neural inhibition between the entire brain network we use to socially, emotionally and morally engage with others, and the entire network we use for scientific, mathematical and logical reasoning. "This shows scientific accounts really do leave something out -- the human touch. A major challenge for the science of the mind is how we can better translate between the cold and distant mechanical descriptions that neuroscience produces, and the emotionally engaged intuitive understanding which allows us to relate to one another as people." The researchers recruited 45 healthy college students, and asked each to take five 10-minute turns inside a magnetic resonance imager. Meanwhile, the researchers randomly presented them with 20 written and 20 video problems that required them to think about how others might feel and with 20 written and 20 video problems that required physics to solve. 【429】
【计时三】
After reading the text or viewing the video, the students had to provide an answer to a yes-no question within seven seconds. Each student's session in the MRI included twenty 27-second rest periods, as well as variable delays between trials lasting 1, 3 or 5 seconds. Students were told to look at a red cross on the screen in front of them and relax during the rests. The MRI images showed that social problems deactivated brain regions associated with analysis, and activated the social network. This finding held true whether the questions came via video or print. Meanwhile, the physics questions deactivated the brain regions associated with empathizing and activated the analytical network. "When subjects are lying in a scanner with nothing to do, which we call the resting state, they naturally cycle between the two networks," Jack said. "This tells us that it's the structure of the adult brain that is driving this, that it's a physiological constraint on cognition." The finding has bearings on a variety of neuropsychiatric disorders, from anxiety, depression and ADHD to schizophrenia -- all of which are characterized by social dysfunction of some sort, Jack said. "Treatment needs to target a balance between these two networks. At present most rehabilitation, and more broadly most educational efforts of any sort, focus on tuning up the analytic network. Yet, we found more cortex dedicated to the social network." Perhaps most clearly, the theory makes sense in regards to developmental disabilities such as autism and Williams syndrome. Autism is often characterized by a strong ability to solve visuospatial problems, such as mentally manipulating two and three-dimensional figures, but poor social skills. People with Williams syndrome are very warm and friendly, but perform poorly on visuospatial tests. But, even healthy adults can rely too much on one network, Jack said. A look at newspaper business pages offers some examples. "You want the CEO of a company to be highly analytical in order to run a company efficiently, otherwise it will go out of business," he said. "But, you can lose your moral compass if you get stuck in an analytic way of thinking." "You'll never get by without both networks," Jack continued. "You don't want to favor one, but cycle efficiently between them, and employ the right network at the right time." The researchers continue to test the theory, studying whether brains will shift from the social network to the analytical when students in the MRI see people depicted in a dehumanizing way, that is, as animals or objects. The group is also studying whether disgust and social stereotyping confound our moral compass by recruiting the analytical network and depressing social network activity. 【445】
【计时四】
Mars Like Hawaii? NASA Rover's First Soil Studies Help Fingerprint Martian Minerals
ScienceDaily (Oct. 30, 2012) — NASA's Mars rover Curiosity has completed initial experiments showing the mineralogy of Martian soil is similar to weathered basaltic soils of volcanic origin in Hawaii. [attachimg=582,600]109183[/attachimg]
The minerals were identified in the first sample of Martian soil ingested recently by the rover. Curiosity used its Chemistry and Mineralogy instrument (CheMin) to obtain the results, which are filling gaps and adding confidence to earlier estimates of the mineralogical makeup of the dust and fine soil widespread on the Red Planet. "We had many previous inferences and discussions about the mineralogy of Martian soil," said David Blake of NASA Ames Research Center in Moffett Field, Calif., who is the principal investigator for CheMin. "Our quantitative results provide refined and in some cases new identifications of the minerals in this first X-ray diffraction analysis on Mars." The identification of minerals in rocks and soil is crucial for the mission's goal to assess past environmental conditions. Each mineral records the conditions under which it formed. The chemical composition of a rock provides only ambiguous mineralogical information, as in the textbook example of the minerals diamond and graphite, which have the same chemical composition, but strikingly different structures and properties. CheMin uses X-ray diffraction, the standard practice for geologists on Earth using much larger laboratory instruments. This method provides more accurate identifications of minerals than any method previously used on Mars. X-ray diffraction reads minerals' internal structure by recording how their crystals distinctively interact with X-rays. Innovations from Ames led to an X-ray diffraction instrument compact enough to fit inside the rover. These NASA technological advances have resulted in other applications on Earth, including compact and portable X-ray diffraction equipment for oil and gas exploration, analysis of archaeological objects and screening of counterfeit pharmaceuticals, among other uses. "Our team is elated with these first results from our instrument," said Blake. "They heighten our anticipation for future CheMin analyses in the months and miles ahead for Curiosity." The specific sample for CheMin's first analysis was soil Curiosity scooped up at a patch of dust and sand that the team named Rocknest. The sample was processed through a sieve to exclude particles larger than 0.006 inch (150 micrometers), roughly the width of a human hair. The sample has at least two components: dust distributed globally in dust storms and fine sand originating more locally. Unlike conglomerate rocks Curiosity investigated a few weeks ago, which are several billion years old and indicative of flowing water, the soil material CheMin has analyzed is more representative of modern processes on Mars. 【436】
【剩余部分】
"Much of Mars is covered with dust, and we had an incomplete understanding of its mineralogy," said David Bish, CheMin co-investigator with Indiana University in Bloomington. "We now know it is mineralogically similar to basaltic material, with significant amounts of feldspar, pyroxene and olivine, which was not unexpected. Roughly half the soil is non-crystalline material, such as volcanic glass or products from weathering of the glass. " Bish said, "So far, the materials Curiosity has analyzed are consistent with our initial ideas of the deposits in Gale Crater recording a transition through time from a wet to dry environment. The ancient rocks, such as the conglomerates, suggest flowing water, while the minerals in the younger soil are consistent with limited interaction with water." During the two-year prime mission of the Mars Science Laboratory Project, researchers are using Curiosity's 10 instruments to investigate whether areas in Gale Crater ever offered environmental conditions favorable for microbial life. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the project for NASA's Science Mission Directorate, Washington, and built Curiosity and CheMin. 【179】
【计时五】
Researchers Engineer Cartilage from Pluripotent Stem Cells
ScienceDaily (Oct. 30, 2012) — A team of Duke Medicine researchers has engineered cartilage from induced pluripotent stem cells that were successfully grown and sorted for use in tissue repair and studies into cartilage injury and osteoarthritis. The finding is reported online in the Proceedings of the National Academy of Sciences, and suggests that induced pluripotent stem cells, or iPSCs, may be a viable source of patient-specific articular cartilage tissue.
[attachimg=562,679]109184[/attachimg]
"This technique of creating induced pluripotent stem cells -- an achievement honored with this year's Nobel Prize in medicine for Shimya Yamanaka of Kyoto University -- is a way to take adult stem cells and convert them so they have the properties of embryonic stem cells," said Farshid Guilak, PhD, Laszlo Ormandy Professor of Orthopaedic Surgery at Duke and senior author of the study. "Adult stems cells are limited in what they can do, and embryonic stem cells have ethical issues," Guilak said. "What this research shows in a mouse model is the ability to create an unlimited supply of stem cells that can turn into any type of tissue -- in this case cartilage, which has no ability to regenerate by itself." Articular cartilage is the shock absorber tissue in joints that makes it possible to walk, climb stairs, jump and perform daily activities without pain. But ordinary wear-and-tear or an injury can diminish its effectiveness and progress to osteoarthritis. Because articular cartilage has a poor capacity for repair, damage and osteoarthritis are leading causes of impairment in older people and often requires joint replacement. In their study, the Duke researchers, led by Brian O. Diekman, PhD, a post-doctoral associate in orthopaedic surgery, aimed to apply recent technologies that have made iPSCs a promising alternative to other tissue engineering techniques, which use adult stem cells derived from the bone marrow or fat tissue. One challenge the researchers sought to overcome was developing a uniformly differentiated population of chondrocytes, cells that produce collagen and maintain cartilage, while culling other types of cells that the powerful iPSCs could form. 【344】
【剩余部分】
To achieve that, the researchers induced chondrocyte differentiation in iPSCs derived from adult mouse fibroblasts by treating cultures with a growth medium. They also tailored the cells to express green fluorescent protein only when the cells successfully became chondrocytes. As the iPSCs differentiated, the chondrocyte cells that glowed with the green fluorescent protein were easily identified and sorted from the undesired cells. The tailored cells also produced greater amounts of cartilage components, including collagen, and showed the characteristic stiffness of native cartilage, suggesting they would work well repairing cartilage defects in the body. "This was a multi-step approach, with the initial differentiation, then sorting, and then proceeding to make the tissue," Diekman said. "What this shows is that iPSCs can be used to make high quality cartilage, either for replacement tissue or as a way to study disease and potential treatments." Diekman and Guilak said the next phase of the research will be to use human iPSCs to test the cartilage-growing technique. "The advantage of this technique is that we can grow a continuous supply of cartilage in a dish," Guilak said. "In addition to cell-based therapies, iPSC technology can also provide patient-specific cell and tissue models that could be used to screen for drugs to treat osteoarthritis, which right now does not have a cure or an effective therapy to inhibit cartilage loss." 【224】
【越障】
Mass Extinction Study Provides Lessons for Modern World
ScienceDaily (Oct. 29, 2012) — The Cretaceous Period of Earth history ended with a mass extinction that wiped out numerous species, most famously the dinosaurs. A new study now finds that the structure of North American ecosystems made the extinction worse than it might have been. Researchers at the University of Chicago, the California Academy of Sciences and the Field Museum of Natural History will publish their findings Oct. 29 online in the Proceedings of the National Academy of Sciences.
[attachimg=400,342]109185[/attachimg]
The mountain-sized asteroid that left the now-buried Chicxulub impact crater on the coast of Mexico's Yucatan Peninsula is almost certainly the ultimate cause of the end-Cretaceous mass extinction, which occurred 65 million years ago. Nevertheless, "Our study suggests that the severity of the mass extinction in North America was greater because of the ecological structure of communities at the time," noted lead author Jonathan Mitchell, a Ph.D. student of UChicago's Committee on Evolutionary Biology.
Mitchell and his co-authors, Peter Roopnarine of the California Academy of Sciences and Kenneth Angielczyk of the Field Museum, reconstructed terrestrial food webs for 17 Cretaceous ecological communities. Seven of these food webs existed within two million years of the Chicxulub impact and 10 came from the preceding 13 million years.
The findings are based on a computer model showing how disturbances spread through the food web. Roopnarine developed the simulation to predict how many animal species would become extinct from a plant die-off, a likely consequence of the impact.
"Our analyses show that more species became extinct for a given plant die-off in the youngest communities," Mitchell said. "We can trace this difference in response to changes in a number of key ecological groups such as plant-eating dinosaurs like Triceratops and small mammals."
The results of Mitchell and his colleagues paint a picture of late Cretaceous North America in which pre-extinction changes to food webs -- likely driven by a combination of environmental and biological factors -- results in communities that were more fragile when faced with large disturbances.
"Besides shedding light on this ancient extinction, our findings imply that seemingly innocuous changes to ecosystems caused by humans might reduce the ecosystems' abilities to withstand unexpected disturbances," Roopnarine said.
The team's computer model describes all plausible diets for the animals under study. In one run, Tyrannosaurus might eat only Triceratops, while in another it eats only duck-billed dinosaurs, and in a third it might eat a more varied diet. This stems from the uncertainty regarding exactly what Cretaceous animals ate, but this uncertainty actually worked to the study's benefit.
"Using modern food webs as guides, what we have discovered is that this uncertainty is far less important to understanding ecosystem functioning than is our general knowledge of the diets and the number of different species that would have had a particular diet," Angielczyk said.
Data derived from modern food webs helped the simulations account for such phenomena as how specialized animals tend to be, or how body size relates to population size and thus their probability of extinction.
The researchers also selected for their study a large number of specific food webs from all the specific webs possible in their general framework and evaluated how this sample of webs respond to a perturbation, such as the death of plants. They used the same relationships and assumptions to create food webs across all of the different sites, which means the differences between sites just stem from differences in the data rather than from the simulation itself. This makes the simulation a fundamentally comparative method, Roopnarine noted.
"We aren't trying to say that a given ecosystem was fragile, but instead that a given ecosystem was more or less fragile than another," he said.
【623】
【剩余部分】
The computer models showed that if the asteroid hit during the 13 million years preceding the latest Cretaceous communities, there almost certainly would still have been a mass extinction, but one that likely would have been less severe in North America.
Most likely a combination of changing climate and other environmental factors caused some types of animals to become more or less diverse in the Cretaceous, the researchers concluded. In their paper they suggest that the drying up of a shallow sea that covered part of North America may have been one of the main factors leading to the observed changes in diversity.
The study provides no evidence that the latest Cretaceous communities were on the verge of collapse before the asteroid hit. "The ecosystems collapsed because of the asteroid impact, and nothing in our study suggests that they would not have otherwise continued on successfully," Mitchell said. "Unusual circumstances, such as the after-effects of the asteroid impact, were needed for the vulnerability of the communities to become important."
The study has implications for modern conservation efforts, Angielczyk observed.
"Our study shows that the robustness or fragility of an ecosystem under duress depends very much on both the number of species present, as well as the types of species," he said, referring to their ecological function. The study also shows that more is not necessarily better, because simply having many species does not insure against ecosystem collapse.
"What you have is also important," Angelczyk said. "It is therefore critical that conservation efforts pay attention to ecosystem functioning and the roles of species in their communities as we continue to degrade our modern ecosystems."
【273】
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