Posts tagged science

March 30, 2012

(HealthDay) — Electrocorticography (ECoG) signals from patients with chronic motor dysfunction represent motor information that may be useful for controlling prosthetic arms, according to a study published in the March issue of the Annals of Neurology.

To investigate whether ECoG signals recorded from chronically paralyzed patients and whether those signals can be applied to control a prosthetic, Takufumi Yanagisawa, M.D., Ph.D., of the Osaka University Medical School in Japan, and colleagues recorded ECoG signals from sensorimotor cortices of 12 patients while they attempted to carry out three to five simple hand and elbow movements. Sensorimotor function was normal in five patients, moderately impaired due to central nervous system lesions sparing the cortex in four patients, and severely impaired due to peripheral nervous system lesion or amputation in three patients.

The researchers found that the high gamma power (80 to 150 Hz) of the ECoG signals during movements was responsive to different types of movement and provided the best information for movement classification. In all patients, the classification performance was significantly better than chance, although for patients with severely impaired motor function the differences between ECoG power modulations during different types of movement were significantly fewer. Cortical representations tended to overlap each other in impaired patients. One moderately impaired patient and three non-paralyzed patients successfully controlled a prosthetic arm using the classification method in real time.

"ECoG signals appear useful for prosthetic arm control and may provide clinically feasible motor restoration for patients with paralysis but no injury of the sensorimotor cortex," the authors write.

Abstract

Source: medicalxpress.com

March 30, 2012

An estimated 2.2 million people in the United States live with epilepsy, a complex brain disorder characterized by sudden and often unpredictable seizures. The highest rate of onset occurs in children and older adults, and it affects people of all ethnicities and socio-economic backgrounds, yet this common disorder is widely misunderstood. Epilepsy refers to a spectrum of disorders with seizures that vary in type, cause, severity, and frequency. Many people do not know the causes of epilepsy or what measures to take if they witness a seizure. A new report from the Institute of Medicine highlights numerous gaps in the knowledge and management of epilepsy and recommends actions for improving the lives of those with epilepsy and their families and promoting better understanding of the disorder.

Effective treatments for epilepsy are available but access to treatment and timely referrals to specialized care are often lacking, the report’s expert committee found. Reaching rural and underserved populations, as well as providing state-of-the art care for people with persistent seizures, is particularly crucial. The report’s recommendations for expanding access to patient-centered health care include early identification and treatment of epilepsy and associated health conditions, implementing measures that assess quality of care, and establishing accreditation criteria and processes for specialized epilepsy centers. In addition, the wide variety of health professionals who care for those with epilepsy need improved knowledge and skills to provide the highest quality health care.

Some causes of epilepsy, such as traumatic brain injury, infection, and stroke, are preventable. Prevention efforts should continue for these established risk factors, as well as for recurring seizures in people with epilepsy and depression, and for epilepsy-related causes of death, the report says.

People with epilepsy need additional education and skills to optimally manage their disorder. Consistent delivery of accurate, clearly communicated health information from sources that include health care professionals and epilepsy organizations can better prepare those with epilepsy and their families to cope with the disorder and its consequences, the report says. Accurate, current data on the extent and consequences of epilepsy and its associated health conditions are especially needed to inform policymakers and identify opportunities for reducing the burden of epilepsy.

Living with epilepsy can affect employment, driving ability, and many other aspects of quality of life. The report stresses the importance of improved access to a range of community services, including vocational, educational, transportation, transitional care, and independent living assistance as well as support groups. The committee urged collaboration among federal agencies, state health departments, and relevant epilepsy organizations to improve and integrate these services and programs, particularly at state and local levels.

Misperceptions about epilepsy persist and a focus on raising public awareness and knowledge is needed, the report adds. Educating community members such as teachers, employers, and others on how to manage seizures could help improve public understanding of epilepsy. The report suggests several strategies for stakeholders to improve public knowledge of the disorder, including forming partnerships with the media, establishing advisory councils, and engaging people with epilepsy and their families to serve as advocates and educators within their communities.

Provided by National Academy of Sciences

Source: medicalxpress.com

March 30, 2012

Researchers want to help the Army better camouflage its soldiers and break the enemy’s efforts to hide.

Researchers Jay Hegde and Xing Chen are using functional MRI to look at the brains of study participants learning how to break camouflage in order to help identify soldiers who will be good at it and identify better ways to teach it. Credit: Phil Jones, GHSU Photographer

"We want to make our camouflage unbreakable and we want to break the camouflage of the enemy," said Dr. Jay Hegde, neuroscientist in the Medical College of Georgia at Georgia Health Sciences University.

Hegde and GHSU Postdoctoral Fellow Dr. Xing Chen are using a relatively simple technique they developed to teach civilian volunteers to break camouflage. They flash a series of camouflage pictures on a computer screen, providing about a half second after each to spot, for instance, a face in a sea of mushrooms. A green light signals a correct answer and a red light signals an incorrect answer. The computer-generated images include distractions to make the difficult task even more challenging.

They are finding that an hour of daily training in as little as two weeks results in proficiency for 60 percent of the mostly college and graduate school students who have signed up for their training. The Army’s current approach is taking soldiers into battlefield situations to hone these skills.

As part of a three-year grant from the Office of Army Research, the researchers want to determine which parts of the brain light up when trained snipers break camouflage.

"We need to figure out how the expert camouflage-breakers do it," Hegde said. "We want to figure out what parts of the brain are most responsive when people break camouflage and, a related experiment is what part of the brain changes its response when people learn to break camouflage." Their techniques include functional magnetic resonance imaging to measure blood flow activity as an indicator of brain cell activity.

Figuring out which parts of the brain are involved could give the Army and others a better way to identify future first-rate snipers and objectively assess instructional efforts.

"If you are the Dean of the Army Sniper Corps and want to develop top-notch snipers, you don’t want to spend a year training them before giving up on half of them," Hegde said. A brain scan could help signal whose relevant areas are well developed and, consequently, have natural skill. 

Early evidence points toward two regions of the temporal lobe, found on either side of the brain and known to have a role in speech and vision. A region called the fusiform gyrus – which plays a role in facial recognition and lights up when people become experts at recognizing various objects, such as a particular bird species – may be important in breaking camouflage as well.

Hegde suspects that expertise at breaking camouflage stems from the fusiform gyrus in combination with some other area(s) of the brain. And, because good recognition skills don’t typically translate from one area to another, he also suspects that the parts of the brain involved vary with the object of their attention. For example, the ability to easily recognize the make and model of a car doesn’t guarantee skill at breaking camouflage and Hegde notes that some military snipers aren’t good at game-hunting.

Vision happens when light enters the retina where photoreceptor cells turn it into signals that are interpreted by the brain. “If there is a whole lot of light falling on them, they send a lot of signals, beep, beep, beep,” he said in rapid succession. “If there is a little bit of light they fire slowly.” The brain connects the dots to form a familiar face or landscape. Camouflage complicates the task – the difference between recognizing a mountain goat against a clear blue sky and finding a moth among a pile of fall leaves.

"Here is the beautiful thing that we are finding out: if you know what you are looking for, the next time you can break the camouflage of the moth. Without knowing what you are looking for, the picture also is ambiguous," Hegde said.

Provided by Georgia Health Sciences University

Source: medicalxpress.com

ScienceDaily (Mar. 30, 2012) — Human attention to a particular portion of an image alters the way the brain processes visual cortex responses to that image.

A schematic diagram of the contrast discrimination task, showing the focal cue trial (top row) and the distributed cue trial (bottom row). The contrast within the top right circle increases from the first interval (second column) to the second interval (fourth column). The third column is the interstimulus interval. (Credit: Copyright 2011 Elsevier Inc.)

Our ability to ignore some, but not other stimuli, allows us to focus our attention and improve our performance on a specific task. The ability to respond to visual stimuli during a visual task hinges on altered brain processing of responses within the visual cortex at the back of the brain, where visual information is first received from the eyes. How this occurs was recently demonstrated by an international team of researchers led by Justin Gardner at the RIKEN Brain Science Institute in Wako.

In a contrast discrimination task, the researchers showed three observers a stimulus of a group of four circles, each containing grey and white bars that created stripes of different contrasts. After a short pause, the researchers showed the circles again, but the contrast within one of the circles was different. The observers were instructed to choose which group of circles contained the higher contrast.

In ‘focal cue trials’, an arrow directed the observers’ attention to a particular circle. In ‘distributed cue’ trials’, four arrows directed their attention diffusely, across all four circles. Gardner and colleagues found that the observers’ performance was better in the focal cue trials.

Using a magnetic resonance imaging (MRI) scanner, the research team was able to map the precise location within the visual cortex that was activated by the visual information within each of the four circles. During the contrast discrimination task, Gardner and colleagues could therefore measure the observers’ visual cortex activity elicited by the stimuli. In this way, they could correlate brain activity in the visual cortex with the observers’ attention and their choice of contrasting circles.

Visual cortex responses tended to be largest when the observers were paying attention to a particular target circle, and smallest when they were ignoring a circle. The researchers determined that the largest visual cortex responses to the stimuli guided the eventual choice of each observer, leading to enhanced performance on the visual task.

"We used computational modeling to test various hypotheses about how attention affects brain processing of visual information to improve behavioral performance," explains Gardner. "We concluded that the observers’ attention causes their brains to select the largest cortical response to guide contrast choice, since we found that an ‘efficient selection’ model best explained the behavioral and fMRI data," he says.

If the findings extend to other senses, such as hearing, researchers may begin to understand how humans make sense of a perceptually cluttered world.

Source: Science Daily

ScienceDaily (Mar. 29, 2012) — A type of cell plentiful in the brain, long considered mainly the stuff that holds the brain together and oft-overlooked by scientists more interested in flashier cells known as neurons, wields more power in the brain than has been realized, according to new research published March 29 in Science Signaling.

Human astrocytes. (Credit: Image courtesy of University of Rochester Medical Center)

Neuroscientists at the University of Rochester Medical Center report that astrocytes are crucial for creating the proper environment for our brains to work. The team found that the cells play a key role in reducing or stopping the electrical signals that are considered brain activity, playing an active role in determining when cells called neurons fire and when they don’t.

That is a big step forward from what scientists have long considered the role of astrocytes — to nurture neurons and keep them healthy.

"Astrocytes have long been called housekeeping cells — tending to neurons, nurturing them, and cleaning up after them," said Maiken Nedergaard, M.D., D.M.Sc., professor of Neurosurgery and leader of the study. "It turns out that they can influence the actions of neurons in ways that have not been realized."

Proper brain function relies on billions of electrical signals — tiny molecular explosions, really — happening remarkably in sync. Recalling the face of a loved one, swinging a baseball bat, walking down the street — all those actions rely on electrical signals passed instantly along our nerves like a molecular hot potato from one brain cell to another.

For that to happen, the molecular brew of chemicals like sodium, calcium and potassium that brain cells reside in must be just right — and astrocytes help to maintain that balanced environment. For instance, when a neuron sends an impulse, or fires, levels of potassium surrounding the cell jump dramatically, and those levels must come down immediately for the brain to work properly. Scientists have long known that that’s a job for astrocytes — sopping up excess potassium, ending the nerve pulse, and restoring the cells so they can fire again immediately.

In the paper in Science Signaling, Nedergaard’s team discovered an expanded role for astrocytes. The team learned that in addition to simply absorbing excess potassium, astrocytes themselves can cause potassium levels around the neuron to drop, putting neuronal signaling to a stop.

"Far from only playing a passive role, astrocytes can initiate the uptake of potassium in a way that affects neuronal activity," said Nedergaard. "It’s a simple, yet powerful mechanism for astrocytes to rapidly modulate neuronal activity."

Nedergaard has investigated the secret lives of astrocytes for more than two decades. She has shown how the cells communicate using calcium to signal. Nearly 20 years ago in a paper in Science, she pioneered the idea that glial cells like astrocytes communicate with neurons and affect them. Since then, has been a lot of speculation by other scientists that chemicals call gliotransmitters, such as glutamate and ATP, are key to this process.

In contrast, in the latest research Nedergaard’s team found that another signaling system involving potassium is at work. By sucking up potassium, astrocytes quell the firing of neurons, increasing what scientists call “synaptic fidelity.” Important brain signals are crisper and clearer because there is less unwanted activity or “chatter” among neurons that should not be firing. Such errant neuronal activity is linked to a plethora of disorders, including epilepsy, schizophrenia, and attention-deficit disorder.

"This gives us a new target for a disease like epilepsy, where signaling among brain cells is not as controlled as it should be," said Nedergaard, whose team is based in the Division of Glia Disease and Therapeutics of the Center for Translational Neuromedicine. of the Department of Neurosurgery

The first authors of the paper are Fushun Wang, Ph.D., research assistant professor of Neurosurgery; and graduate student Nathan Anthony Smith. They did much of the work by using a sophisticated laser-based system to monitor the activity of astrocytes in the living brain of rats and mice. The work by Smith, a graduate student in the University’s neuroscience program, was supported by a Kirschstein National Research Service Award from the National Institute of Neurological Disorders and Stroke (NINDS).

Other authors from Rochester include Takumi Fujita, Ph.D., post-doctoral associate; Takahiro Takano, Ph.D., assistant professor; Qiwu Xu, technical associate; and Lane Bekar, Ph.D., formerly research assistant professor, now at the University of Saskatchewan. Also contributing were Akemichi Baba of Hyogo University of Health Sciences in Japan, and Toshio Matsuda of Osaka University in Japan.

Nedergaard notes that the complexity and size of our astrocytes is one of few characteristics that differentiate our brains from rodents. Our astrocytes are bigger, faster, and much more complex in both structure and function. She has found that astrocytes contribute to conditions like stroke, Alzheimer’s, epilepsy, and spinal cord injury.

"Astrocytes are integral to the most sophisticated brain processes," she added.

Source: Science Daily

ScienceDaily (Mar. 29, 2012) — Certain genes and proteins that promote growth and development of embryos also play a surprising role in sending chemical signals that help adults learn, remember, forget and perhaps become addicted, University of Utah biologists have discovered.

This is a microscope image of the roundworm or nematode C. elegans with its nervous system glowing green due to labeling with a green jellyfish protein. (Credit: Penelope Brockie, University of Utah.)

"We found that these molecules and signaling pathways [named Wnt] do not retire after development of the organism, but have a new and surprising role in the adult. They are called back to action to change the properties of the nervous system in response to experience," says biology Professor Andres Villu Maricq, senior author of the new study in the March 30 issue of the journal Cell.

The study was performed in C. elegans — the millimeter-long roundworm or nematode — which has a nervous system that serves as a model for those of vertebrate animals, including humans.

Because other Wnt pathways in worms are known to work in humans too, the researchers believe that Wnt genes, the Wnt proteins they produce and so-called “Wnt signaling” also are involved in human learning, memory and forgetting.

"Almost certainly what we have discovered is going on in our brain as well," Maricq says. And because a worm nerve-signal "receptor" in the study is analogous to a human nicotine receptor involved in addiction, schizophrenia and some other mental disorders, some of the genes identified in the worm study "represent possible new targets for treatment of schizophrenia and perhaps addiction," he adds.

Wnt genes and their proteins already were known to “pattern the development and distribution of organs in the body” during embryo development, and to be responsible for various cancers and developmental defects when mutated, he says.

Maricq conducted the study with these Utah biologists: doctoral students Michael Jensen and Dane Maxfield; postdoctoral researchers Michael M. Francis, Frederic Hoerndli and Rui Wang; undergraduate Erica Johnson; Penelope Brockie, a research associate professor; and David M. Madsen, a senior research specialist.

Read more …

March 29, 2012

(Medical Xpress) — Brain stimulation can markedly improve people’s ability to solve highly complex problems, a recent University of Sydney study suggests.

(L-R) Professor Allan Snyder and Richard Chi found brain stimulation helped people solve a puzzle.

The findings by Professor Allan Snyder and Richard Chi, from the University of Sydney, are published in Neuroscience Letters.

"The results suggest non-invasive brain stimulation could assist people in solving tasks that appear straightforward but are inherently difficult," said Professor Snyder.

Our minds have evolved to solve certain problems effortlessly, yet we struggle to solve others that appear simple but require us to apply an unfamiliar paradigm, to ‘think outside the box’.

The famous ‘nine dots puzzle’. Can you join them using only four straight lines without taking your pen off the page?

"As an example we have taken the famous nine dots problem, where you are asked to join all the dots with four straight lines without taking the pen off the page," Professor Snyder said.

"Surprisingly, investigations over the last century show that almost no one can do this."

Now the researchers have shown that more than 40 percent of the people they tested were able to solve the nine dots problem after receiving 10 minutes of safe, non-invasive brain stimulation.

Specifically the left anterior temporal lobe of the brain is inhibited while simultaneously the right anterior temporal lobe is excited, employing a technique known as transcranial direct current stimulation.

Using the same procedure the researchers have previously reported success in amplifying insight and memory.

Chi and Snyder suggest that their unique brain stimulation protocol could ultimately enable people to “escape the tricks our minds impose on us,” as Professor Snyder describes it, and solve tasks that appear deceptively simple.

Provided by University of Sydney

Source: medicalxpress.com

March 29, 2012

The first atlas of the surface of the human brain based upon genetic information has been produced by a national team of scientists, led by researchers at the University of California, San Diego School of Medicine and the VA San Diego Healthcare System. The work is published in the March 30 issue of the journal Science.

This is a genetic clustering map of the brain, left lateral view. Credit: UC San Diego School of Medicine

The atlas reveals that the cerebral cortex – the sheet of neural tissue enveloping the brain – is roughly divided into genetic divisions that differ from other brain maps based on physiology or function. The genetic atlas provides scientists with a new tool for studying and explaining how the brain works, particularly the involvement of genes.

"Genetics are important to understanding all kinds of biological phenomena," said William S. Kremen, PhD, professor of psychiatry at the UC San Diego School of Medicine and co-senior author with Anders M. Dale, PhD, professor of radiology, neurosciences, and psychiatry, also at the UC San Diego School of Medicine.

According to Chi-Hua Chen, PhD, first author and a postdoctoral fellow in the UC San Diego Department of Psychiatry, “If we can understand the genetic underpinnings of the brain, we can get a better idea of how it develops and works, information we can then use to ultimately improve treatments for diseases and disorders.”

The human cerebral cortex, characterized by distinctive twisting folds and fissures called sulci, is just 0.08 to 0.16 inches thick, but contains multiple layers of interconnected neurons with key roles in memory, attention, language, cognition and consciousness.

Other atlases have mapped the brain by cytoarchitecture – differences in tissues or function. The new map is based entirely upon genetic information derived from magnetic resonance imaging (MRI) of 406 adult twins participating in the Vietnam Era Twin Registry (VETSA), an ongoing longitudinal study of cognitive aging supported in part by grants from the National Institutes of Health (NIH). It follows a related study published last year by Kremen, Dale and colleagues that affirmed the human cortical regionalization is similar to and consistent with patterns found in other mammals, evidence of a common conservation mechanism in evolution.

"We are excited by the development of this new atlas, which we hope will help us understand aging-related changes in brain structure and cognitive function now occurring in the VETSA participants," said Jonathan W. King, PhD, of the National Institute on Aging, part of the NIH.

The atlas plots genetic correlations between different points on the cortical surface of the twins’ brains. The correlations represent shared genetic influences and reveal that genetic brain divisions do not map one-to-one with traditional brain divisions that are based on structure and function. “Yet, the pattern of this genetic map still suggests that it is neuroanatomically meaningful,” said Kremen.

Kremen said the genetic brain atlas may be especially useful for scientists who employ genome-wide association studies, a relatively new tool that looks for common genetic variants in people that may be associated with a particular trait, condition or disease.

Provided by University of California - San Diego

Source: medicalxpress.com

March 29, 2012

The brain appears to be wired more like the checkerboard streets of New York City than the curvy lanes of Columbia, Md., suggests a new brain imaging study. The most detailed images, to date, reveal a pervasive 3D grid structure with no diagonals, say scientists funded by the National Institutes of Health.

Curvature in this DSI image of a whole human brain turns out to be folding of 2-D sheets of parallel neuronal fibers that cross paths at right angles. This picture came from the new Connectom scanner. Credit: Van Wedeen, M.D., Martinos Center and Dept. of Radiology, Massachusetts General Hospital and Harvard University Medical School

"Far from being just a tangle of wires, the brain’s connections turn out to be more like ribbon cables — folding 2D sheets of parallel neuronal fibers that cross paths at right angles, like the warp and weft of a fabric," explained Van Wedeen, M.D., of Massachusetts General Hospital (MGH), A.A. Martinos Center for Biomedical Imaging and the Harvard Medical School. "This grid structure is continuous and consistent at all scales and across humans and other primate species."

Wedeen and colleagues report new evidence of the brain’s elegant simplicity March 30, 2012 in the journal Science. The study was funded, in part, by the NIH’s National Institute of Mental Health (NIMH), the Human Connectome Project of the NIH Blueprint for Neuroscience Research, and other NIH components.

"Getting a high resolution wiring diagram of our brains is a landmark in human neuroanatomy," said NIMH Director Thomas R. Insel, M.D. "This new technology may reveal individual differences in brain connections that could aid diagnosis and treatment of brain disorders."

Read more …

March 28, 2012 By Kimm Fesenmaier

(Medical Xpress) — When jurors sentencing convicted criminals are instructed to weigh not only facts but also tricky emotional factors, they rely on parts of the brain associated with sympathy and making moral judgments, according to a new paper by a team of neuroscientists. Using brain-imaging techniques, the researchers, including Caltech’s Colin Camerer, found that the most lenient jurors show heightened levels of activity in the insula, a brain region associated with discomfort and pain and with imagining the pain that others feel.

The findings provide insight into the role that emotion plays in jurors’ decision-making processes, indicating a close relationship between sympathy and mitigation.

In the study, the researchers, led by Makiko Yamada of National Institute of Radiological Sciences in Japan, considered cases where juries were given the option to lessen the sentences for convicted murderers. In such cases with “mitigating circumstances,” jurors are instructed to consider factors, sometimes including emotional elements, that might cause them to have sympathy for the criminal and, therefore, shorten the sentence. An example would be a case in which a man killed his wife to spare her from a more painful death, say, from a terminal illness. 

"Finding out if jurors are weighing sympathy reasonably is difficult to do, objectively," says Colin Camerer, the Robert Kirby Professor of Behavioral Finance and Economics at Caltech. "Instead of asking the jurors, we asked their brains."

The researchers scanned the brains of citizens (potential jurors) while the participants read scenarios adapted from actual murder cases with mitigating circumstances. In some cases, the circumstances were sympathy-inducing; in others, where, for example, a man became enraged when an ex-girlfriend refused him, they were not. The scientists used functional magnetic resonance imaging (fMRI), a type of brain scanning that tracks increases in oxygenated blood flow, indicating heightened brain activity. The participants also had their brains scanned when they determined whether to lessen the sentences, and by how much.  

The team found that sympathy activated the dorsomedial prefrontal cortex, precuneus, and temporo-parietal junction—brain regions associated with moral conflict and thinking about the feelings of others. Similarly, the jurors had increased activity in these regions during sentencing when the mitigating circumstances earned their sympathy. In those cases, they also delivered shorter hypothetical sentences.

In addition to Camerer and Yamada, coauthors on the new paper, “Neural circuits in the brain that are activated when mitigating criminal sentences,” are Saori Fujie, Harumasa Takano, Hiroshi Ito, Tetsuya Suhara, and Hidehiko Takahashi of the National Institute of Radiological Sciences; Motoichiro Kato of the Keio University of Medicine; and Tetsuya Matsuda of Tamagawa University Brain Science Institute. Yamada is also affiliated with Tamagawa University Brain Science Institute and Kyoto University School of Medicine; she and Takahashi are additionally affiliated with the Japan Science and Technology Agency.

More information: Neural circuits in the brain that are activated when mitigating criminal sentences 

Provided by California Institute of Technology

Source: medicalxpress.com