Friday, March 26, 2010

EXPLORING STATUS QUO BIAS IN THE HUMAN BRAIN

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The more difficult the decision we face, the more likely we are not to act, according to new research by UCL scientists that examines the neural pathways involved in 'status quo bias' in the human brain.

The study, published in Proceedings of the National Academy of Sciences (PNAS), looked at the decision-making of participants taking part in a tennis 'line judgement' game while their brains were scanned using functional MRI (fMRI).

First author Stephen Fleming, Wellcome Trust Centre for Neuroimaging at UCL, said: "When faced with a complex decision people tend to accept the status quo, hence the old saying 'When in doubt, do nothing.'

"Whether it's moving house or changing TV channel, there is a considerable tendency to stick with the current situation and choose not to act, and we wanted to explore this bias towards inaction in our study and examine the regions of the brain involved."

The 16 study participants were asked to look at a cross between two tramlines on a screen while holding down a 'default' key. They then saw a ball land in the court and had to make a decision as to whether it was in or out. On each trial, the computer signalled which was the current default option – 'in' or 'out'. The participants continued to hold down the key to accept the default and had to release it and change to another key to reject the default.

The results showed a consistent bias towards the default, which led to errors. As the task became more difficult, the bias became even more pronounced. The fMRI scans showed that a region of the brain known as the subthalamic nucleus (STN) was more active in the cases when the default was rejected. Also, greater flow of information was seen from a separate region sensitive to difficulty (the prefrontal cortex) to the STN. This indicates that the STN plays a key role in overcoming status quo bias when the decision is difficult.

Stephen added: "Interestingly, current treatments of Parkinson's disease like deep-brain stimulation (DBS) work by disrupting the subthalamic nucleus to alleviate impaired initiation of action. This is one example of how knowing about disease mechanisms can inform our knowledge of normal decision making, and vice-versa.

"This study looked at a very simple perceptual decision and there are obviously other powerful factors, such as desires and goals that influence decisions about whether or not to act. So, it would be of interest to investigate how these regions respond when values and needs come into play."

University College London

THE FORMULA FOR MAKING TEETH WILL SOON BE FOUND

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Each cusp of our teeth is regulated by genes which carefully control the development. A similar genetic puzzle also regulates the differentiation of our other organs and of all living organisms. A team of researchers at the Institute of Biotechnology of the University of Helsinki has developed a computer model reproducing population-level variation in complex structures like teeth and organs. The research takes a step towards the growing of correctly shaped teeth and other organs. The results were published in Nature, the esteemed science journal.

Academy Professor Jukka Jernvall and his team investigate the evolutionary development of mammal teeth. After over 15 years of work, the team has compiled so much data that the main aspects of a formula for making teeth are beginning to be clear. The model shows that regulation of tooth development is already well known. Teeth are a kind of "model species" for Jernvall's team, which means that the study results also tell about the development of other organs.

According to a mathematical computer model, a rather simple basic formula seems to be behind the complex gene puzzle resulting in tooth formations; the jungle of gene networks has a 'patterning kernel' regulating the variation of teeth among individuals in the same population. Also the variation of human teeth from the incisors to the molar teeth may result from a single factor regulating cell division.

The researchers tested their theoretical model, which is based on mouse tooth development, by investigating seal teeth. The Ladoga ringed seal collection of the Finnish Museum of Natural History at the University of Helsinki provided an ideal population sample for the research because dentitions are highly variable.

The mathematical model proposed by the research team may give new kind of understanding on the formation of organisms' three-dimensional shapes: How do different levels of ontogeny function together? What factors guide the emergence of specific external features? The new research results may promote medical research, such as growing new organs.

Jernvall is known as an international pioneer in cross-disciplinary evolutionary development biology. A few years ago, the science journal Nature chose a teeth evolution work conducted by Jernvall and two post-doc researchers as one of the 15 educational topics in the field of evolutionary biology. The research published now was conducted with Jernvall's third post-doc researcher, Isaac Salazar-Ciudad. Salazar-Ciudad currently works at the Autonomous University of Barcelona in Spain.

University of Helsinki

TIMING IS (ALMOST) EVERYTHING

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What determines whether a scene is remembered or forgotten? According to a study published in the open access journal PLoS Biology, memory for visual scenes may not depend on attention level or what a scene contains, but when the scene is presented. The study, presented by researchers at the University of Washington, shows how visual scenes are encoded into memory at behaviorally relevant points in time.

The ability to remember a briefly presented scene depends on a number of factors, such as its saliency, novelty, degree of threat, or behavioral relevance to a task. Generally, attention is thought to be key, in that people can only remember part of a visual scene when paying attention to it at any given moment.

In this study, participants performed an attention-demanding "target detection task at fixation," while also viewing a rapid sequence of full-field photographs of urban and natural scenes. Participants were then tested on whether they recognized a specific scene from the sequence they had been shown or not. "Usually, the addition of a secondary task decreases performance on the first task. However, in this particular case, adding a second task (letter identification) actually enhanced performance in the first task (scene memory) when targets were accurately detected in the second letter identification task," says Jeffrey Lin, the lead author of the study.

This study adds to our understanding of how selective attention can influence the ability to remember specific features of our environment. The results point to a brain mechanism that automatically encodes certain visual features into memory at behaviorally relevant points in time, regardless of the spatial focus of attention. Timing may not be everything, but it's more important than you realize.

PLoS Biology

SCIENTISTS AT UCSB DISCOVER 600-MILLION-YEAR-OLD ORIGINS OF VISION

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By studying the hydra, a member of an ancient group of sea creatures that is still flourishing, scientists at UC Santa Barbara have made a discovery in understanding the origins of human vision.

The finding is published in Proceedings of the Royal Society B, a British journal of biology.

Hydra are simple animals that, along with jellyfish, belong to the phylum cnidaria. Cnidarians first emerged 600 million years ago.

"We determined which genetic 'gateway,' or ion channel, in the hydra is involved in light sensitivity," said senior author Todd H. Oakley, assistant professor in UCSB's Department of Ecology, Evolution and Marine Biology. "This is the same gateway that is used in human vision."

Oakley explained that there are many genes involved in vision, and that there is an ion channel gene responsible for starting the neural impulse of vision. This gene controls the entrance and exit of ions; i.e., it acts as a gateway.

The gene, called opsin, is present in vision among vertebrate animals, and is responsible for a different way of seeing than that of animals like flies. The vision of insects emerged later than the visual machinery found in hydra and vertebrate animals.

"This work picks up on earlier studies of the hydra in my lab, and continues to challenge the misunderstanding that evolution represents a ladder-like march of progress, with humans at the pinnacle," said Oakley. "Instead, it illustrates how all organisms –– humans included –– are a complex mix of ancient and new characteristics."

(Photo: Todd Oakley, UCSB)

UC Santa Barbara

CAN WE DETECT QUANTUM BEHAVIOR IN VIRUSES?

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The weird world of quantum mechanics describes the strange, often contradictory, behaviour of small inanimate objects such as atoms. Researchers have now started looking for ways to detect quantum properties in more complex and larger entities, possibly even living organisms.

German-Spanish research group, split between the Max Planck Institute for Quantum Optics in Garching and the Institute of Photonic Sciences (ICFO), is using the principles of an iconic quantum mechanics thought experiment - Schrödinger's superpositioned cat – to test for quantum properties in objects composed of as many as one billion atoms, possibly including the flu virus.

New research published Thursday 11 March, in New Journal of Physics (co-owned by the Institute of Physics and German Physical Society), describes the construction of an experiment to test for superposition states in these larger objects.

Quantum optics is a field well-rehearsed in the process of detecting quantum properties in single atoms and some small molecules but the scale that these researchers wish to work at is unprecedented.

When physicists try to fathom exactly how the tiniest constituents of matter and energy behave, confusing patterns of their ability to do two things at once (referred to as being in a superposition state), and of their 'spooky' connection (referred to as entanglement) to their physically distant sub-atomic brethren, emerge.

It is the ability of these tiny objects to do two things at once that Oriol Romero-Isart and his co-workers are preparing to probe.

With this new technique, the researchers suggest that viruses are one type of object that could be probed. Albeit speculatively, the researchers hope that their technique might offer a route to experimentally address questions such as the role of life and consciousness in quantum mechanics.

In order to test for superposition states, the experiment involves finely tuning lasers to capture larger objects such as viruses in an 'optical cavity' (a very tiny space), another laser to slow the object down (and put it into what quantum mechanics call a 'ground state') and then adding a photon (the basic element of light) in a specific quantum state to the laser to provoke it into a superposition.

The researchers say, "We hope that this system, apart from providing new quantum technology, will allow us to test quantum mechanics at larger scales, by preparing macroscopic superpositions of objects at the nano and micro scale. This could then enable us to use more complex microorganisms, and thus test the quantum superposition principle with living organisms by performing quantum optics experiments with them."

IOP Science

EARLY TERRESTRIAL AMPHIBIAN DESCRIBED BY CARNEGIE MUSEUM OF NATURAL HISTORY SCIENTISTS

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A team of researchers from Carnegie Museum of Natural History has described a new genus and species of carnivorous amphibian from western Pennsylvania. The fossil skull, found in 2004 near Pittsburgh International Airport, was recovered from rocks deposited approximately 300 million years ago during the Late Pennsylvanian Period.

Named Fedexia striegeli, it is one of only a very few relatively large amphibian fossils to display evidence of a predominantly terrestrial (land-based) life history so early in geologic time. The rocks where Fedexia was found are nearly 20 million years older than the localities of its fossil relatives, suggesting that the expansion and diversification of this group occurred much earlier than had been recognized previously.

Fedexia was described on the basis of a remarkably well-preserved fossil skull. Unlike similar discoveries, the five-inch-long (11.5 cm) fossil skull remained three-dimensional over time because it was never crushed by rocks that were deposited above it. Fedexia striegeli was named for FedEx, the corporation that owns the land on which the fossil was found, and for amateur discoverer Mr. Adam Striegel, who originally found the specimen on a geology field trip while a senior at the University of Pittsburgh.

Fedexia represents an extinct group of amphibians called Trematopidae that lived about 70 million years before the first dinosaurs appeared. Unlike almost all other Pennsylvanian Period amphibians, which did not often venture out of the water, this rare, diverse group lived mostly on land, returning to the water perhaps only to mate or lay eggs. The trematopids also provide evidence of the earliest vertebrate life in North America adapted to a mostly terrestrial existence. Their success may have been a result of a long-term, global trend toward drier, warmer conditions that reached its climax near the end of the Pennsylvanian Period.

At the time of Fedexia’s preservation, the earth’s climate was in a period of transition. Immense glaciers in Earth’s southern polar region produced rapidly fluctuating global climates. Western Pennsylvania, which was near the equator at that time, experienced tremendous amounts of rain. Swamps which would later develop into coal developed, and amphibians—which are dependent on moist conditions—flourished; in fact, the Pennsylvanian Period is known as the “Age of Amphibians.”

Gradually, however, as an increasing amount of the planet’s water became locked up in polar ice, the sea level dropped and more land was exposed. Vast regions of the earth became drier and warmer, including the region that would become western Pennsylvania. The coal swamps and lakes dried up, and many of the coal-forming plants became extinct. It was at this time that amphibian populations in what would become the Pittsburgh region shifted from mainly aquatic to mainly terrestrial, paralleling the change in climate from tropical to semi-arid. Vertebrates that had already begun adapting to terrestrial life—including amphibians closely related to Fedexia striegeli—became far more abundant, widespread, and diverse than their relatives who were still dependent upon cooler, moist environments.

The large number of trematopid amphibians appearing in the fossil record in the Permian Period suggests that climate change was a major factor in the diversification of terrestrial amphibians. The appearance of Fedexia during the Pennsylvanian Period—20 million years earlier than the Permian—was an early indicator of the diversification that was to come. Co-author David Brezinski states, “The one-to-one correspondence between this early appearance of trematopids in the fossil record and the preservation of dry climate indicators in the surrounding rock units suggests that this is a climatically driven immigration and/or origination event.”

Although the appearance of Fedexia and other highly terrestrial vertebrates in the fossil record seems sudden, this is undoubtedly misleading. They or their close relatives had probably already existed for a few million years, occupying upland regions where conditions for fossil preservation were not optimal. However, the climatic change to drier, warmer conditions led to an explosive dispersal of terrestrial vertebrates to coastal regions and lowlands—including western Pennsylvania—where accumulating sediments increased the chances for fossil preservation. Because western Pennsylvania is the “type stratigraphic sequence”—or best record—of sediments deposited during the Pennsylvanian geologic period, this region offers exceptional opportunities for future discoveries of terrestrial vertebrate fossils of this age.

Fedexia striegeli was described on the basis of a remarkably well-preserved fossil skull. Unlike many other fossil finds, the fossil skull remained three-dimensional and did not suffer post-mortem crushing over time by the compaction of rock formations above it. The preservation of the skull is so precise that even the middle-ear bone, known as the stapes, remains perfectly intact and in its correct position, a very rare discovery in fossils. Owing to the remarkable preservation of the skull, Fedexia was easily identified as a trematopid, mainly by the hallmark feature of the group, a greatly elongated external nasal opening that is partially subdivided into fore and aft portions. Some scientists speculate that the posterior division held a gland—similar to that in some modern-day reptiles and marine birds—that rid the body of excess salt, or perhaps enhanced the sense of smell; either function would have been an advantage for a terrestrial existence. Fedexia is the first trematopid to be found in Pennsylvania, and only the third in the world of Late Pennsylvanian age, the group’s earliest appearance.

Now that the immediate study of Fedexia striegeli is complete, the fossil has been permanently preserved for future research in the Carnegie Museum of Natural History vertebrate paleontology collection. Casts of the skull will be given to FedEx Corporation and to Mr. Striegel.

According to co-author David S Berman, “What is particularly amazing about this discovery is that it was made by an amateur who had no prior experience in recognizing vertebrate fossils in the rock, a talent that usually takes years to develop.”

Carnegie Museum of Natural History

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