Posts tagged brain
Articles and news from the latest research reports.
Human cognition depends upon slow-firing neurons
Good mental health and clear thinking depend upon our ability to store and manipulate thoughts on a sort of “mental sketch pad.” In a new study, Yale School of Medicine researchers describe the molecular basis of this ability — the hallmark of human cognition — and describe how a breakdown of the system contributes to diseases such as schizophrenia and Alzheimer’s disease.
“Insults to these highly evolved cortical circuits impair the ability to create and maintain our mental representations of the world, which is the basis of higher cognition,” said Amy Arnsten, professor of neurobiology and senior author of the paper published in the Feb. 20 issue of the journal Neuron.
High-order thinking depends upon our ability to generate mental representations in our brains without any sensory stimulation from the environment. These cognitive abilities arise from highly evolved circuits in the prefrontal cortex. Mathematical models by former Yale neurobiologist Xiao-Jing Wang, now of New York University, predicted that in order to maintain these visual representations the prefrontal cortex must rely on a family of receptors that allow for slow, steady firing of neurons. The Yale scientists show that NMDA-NR2B receptors involved in glutamate signaling regulate this neuronal firing. These receptors, studied at Yale for more than a decade, are responsible for activity of highly evolved brain circuits found especially in primates.
Earlier studies have shown these types of NMDA receptors are often altered in patients with schizophrenia. The Neuron study suggests that those suffering from the disease may be unable to hold onto a stable view of the world. Also, these receptors seem to be altered in Alzheimer’s patients, which may contribute to the cognitive deficits of dementia.
The lab of Dr. John Krystal, chair of the department of psychiatry at Yale, has found that the anesthetic ketamine, abused as a street drug, blocks NMDA receptors and can mimic some of the symptoms of schizophrenia. The current study in Neuron shows that ketamine may reduce the firing of the same higher-order neural circuits that are decimated in schizophrenia.
“Identifying the receptor needed for higher cognition may help us to understand why certain genetic insults lead to cognitive impairment and will help us to develop strategies for treating these debilitating disorders,” Arnsten said.
Engineering control theory helps create dynamic brain models
Models of the human brain, patterned on engineering control theory, may some day help researchers control such neurological diseases as epilepsy, Parkinson’s and migraines, according to a Penn State researcher who is using mathematical models of neuron networks from which more complex brain models emerge.
"The dual concepts of observability and controlability have been considered one of the most important developments in mathematics of the 20th century," said Steven J. Schiff, the Brush Chair Professor of Engineering and director of the Penn State Center for Neural Engineering. "Observability and controlability theorems essentially state that if you can observe and reconstruct a system’s variables, you may be able to optimally control it. Incredibly, these theoretical concepts have been largely absent in the observation and control of complex biological systems."
Those engineering concepts were originally designed for simple linear phenomena, but were later revised to apply to non-linear systems. Such things as robotic navigation, automated aircraft landings, climate models and the human brain all require non-linear models and methods.
"If you want to observe anything that is at all complicated — having more than one part — in nature, you typically only observe one of the parts or a small subset of the many parts," said Schiff, who is also professor of neurosurgery, engineering science and mechanics, and physics, and a faculty member of the Huck Institutes of the Life Sciences. "The best way of doing that is make a model. Not a replica, but a mathematical representation that uses strategies to reconstruct from measurements of one part to the many that we cannot observe."
This type of model-based observability makes it possible today to create weather predictions of unprecedented accuracy and to automatically land an airliner without pilot intervention.
"Brains are much harder than the weather," said Schiff. "In comparison, the weather is a breeze."
There are seven equations that govern weather, but the number of equations for the brain is uncountable, according to Schiff. One of the problems with modeling the brain is that neural networks in the brain are not connected from neighbor to neighbor. Too many pathways exist.
"We make and we have been making models of the brain’s networks for 60 years," Schiff said at the recent annual meeting of the American Association for the Advancement of Science in Boston. “We do that for small pieces of the brain. How retina takes in an image and how the brain decodes that image, or how we generate simple movements are examples of how we try now to embody the equations of motion of those limited pieces. But we never used the control engineer’s trick of fusing those models with our measurements from the brain. This is the key — a good model will synchronize with the system it is coupled to.”
(Image: Photograph by Anne Keiser, National Geographic; model by Yeorgos Lampathakis)
Momentum builds in quest to find cure for childhood brain disease
Rasmussen Encephalitis strikes healthy kids; only known treatment removing half the brain.
How do you find a cure for a devastating pediatric brain disease so rare that it can take decades to build a meaningful research base?
In 2010, the parents of a patient created the Rasmussen Encephalitis (RE) Children’s Project to help solve this problem. In a short amount of time, the foundation has raised funds to establish a consortium of top researchers, build a collection of samples of the disease from around the world and support projects to study the disease tissue and search for genetic links. The goal is to find a cure.
Researchers at the David Geffen School of Medicine at UCLA have played a vital role in the ongoing research, and the foundation recently provided a second round of funding to continue their work. The gift of $125,000 builds on the organization’s donation of $111,000 made in 2011.
"We are still in the early stages of research, but our momentum is building," said Seth H. Wohlberg, founder of the RE Children’s Project, and father of Grace, 15, who was stricken by the disease when she was 10 years old. "One of our key accomplishments has been to create an international system so that we can coordinate and transfer RE brain tissue and DNA material from the patients and parents. Collecting these samples is vital to advancing the research."
With the additional funding, UCLA researchers will apply cutting-edge DNA sequencing technology to determine whether a virus, or some other infectious agent, causes RE. They also plan to develop an animal model of the disease using cells obtained from the RE samples.
The researchers include Dr. Gary Mathern, professor of pediatric neurosurgery and director of the UCLA Pediatric Epilepsy Program at Mattel Children’s Hospital; Carol Kruse, professor of neurosurgery; and Geoffrey Owens, visiting assistant researcher in neurosurgery.
"I am grateful to collaborate with a devoted father who has taken on the enormous task of advancing research for RE," said Mathern. "Thanks to his leadership, we now have the network to collect the tissue and DNA needed to study the brain, immunologic cells and genetics to unlock what causes this disease and develop new treatments or a cure. The RE Children’s Project has truly helped accelerate our research, bringing new information and resources that could have taken 10 more years to develop to the forefront today."
Rasmussen Encephalitis is a neurological disease that causes intractable seizures, cognitive deficits and paralysis of half of the body. It is very rare and only a few hundred cases have been reported worldwide. RE typically affects previously normal children between the ages of two and ten years old. The disease process can run its course over a one to two year period during which time one half of the body is rendered useless and epileptic seizures continue unabated.
An unusual feature of the disease is that it is usually confined to one hemisphere of the brain and is resistant to standard anti-seizure medicines. Currently the only known “cure” is radical- the surgical removal or disconnection of the affected side of the brain known as a hemispherectomy.
In the summer of 2008, the Wohlberg’s 10-year-old daughter Grace started to experience epileptic seizures. After months of testing, her parents learned that she had the extremely rare neurological disorder. Grace underwent an initial hemispherectomy surgery in February 2009. However, her seizures recurred so her parents then brought Grace to UCLA to complete the hemispherectomy which was performed by Mathern in March 2010.
Today, Grace attends high school with the assistance of a full-time aide. While the surgery has stopped the seizures, Grace faces lifelong disabilities including partial blindness, cognitive issues and learning how to walk again. She is also active in helping her father promote the RE Children’s Project.
"It’s really supportive to let people know our story," said Grace. "Every year, my dad does a fundraiser and a lot of people come out to support it. It’s fun to be there and see all the people who care and want to help."
(Image: Wikimedia Commons)
New study shows how seals sleep with only half their brain at a time
A new study led by an international team of biologists has identified some of the brain chemicals that allow seals to sleep with half of their brain at a time.
The study was published this month in the Journal of Neuroscience and was headed by scientists at UCLA and the University of Toronto. It identified the chemical cues that allow the seal brain to remain half awake and asleep. Findings from this study may explain the biological mechanisms that enable the brain to remain alert during waking hours and go off-line during sleep.
“Seals do something biologically amazing — they sleep with half their brain at a time. The left side of their brain can sleep while the right side stays awake. Seals sleep this way while they’re in water, but they sleep like humans while on land. Our research may explain how this unique biological phenomenon happens” said Professor John Peever of the University of Toronto.
The study’s first author, University of Toronto PhD student Jennifer Lapierre, made this discovery by measuring how different chemicals change in the sleeping and waking sides of the brain. She found that acetylcholine – an important brain chemical – was at low levels on the sleeping side of the brain but at high levels on the waking side. This finding suggests that acetylcholine may drive brain alertness on the side that is awake.
But, the study also showed that another important brain chemical – serotonin – was present at the equal levels on both sides of the brain whether the seals were awake or asleep. This was a surprising finding because scientist long thought that serotonin was a chemical that causes brain arousal.
These findings have possible human health implications because “about 40% of North Americans suffer from sleep problems and understanding which brain chemicals function to keep us awake or asleep is a major scientific advance. It could help solve the mystery of how and why we sleep” says the study’s senior author Jerome Siegel of UCLA’s Brain Research Institute.
(Image: AFP)
Is there a link between childhood obesity and ADHD, learning disabilities?
A University of Illinois study has established a possible link between high-fat diets and such childhood brain-based conditions as attention deficit hyperactivity disorder (ADHD) and memory-dependent learning disabilities.
“We found that a high-fat diet rapidly affected dopamine metabolism in the brains of juvenile mice, triggering anxious behaviors and learning deficiencies. Interestingly, when methylphenidate (Ritalin) was administered, the learning and memory problems went away,” said Gregory Freund, a professor in the U of I College of Medicine and a member of the university’s Division of Nutritional Sciences.
The research was published in Psychoneuroendocrinology.
Freund said that altered dopamine signaling in the brain is common to both ADHD and the overweight or obese state. “And an increase in the number of dopamine metabolites is associated with anxiety behaviors in children,” he added.
Intrigued by the recent upsurge in both child obesity and adverse childhood psychological conditions, including impulsivity, depression, and ADHD, Freund’s team examined the short-term effects of a high-fat (60% calories from fat) versus a low-fat (10% calories from fat) diet on the behavior of two groups of four-week-old mice. A typical Western diet contains from 35 to 45 percent fat, he said.
“After only one week of the high-fat diet, even before we were able to see any weight gain, the behavior of the mice in the first group began to change,” he said.
Evidence of anxiety included increased burrowing and wheel running as well a reluctance to explore open spaces. The mice also developed learning and memory deficits, including decreased ability to negotiate a maze and impaired object recognition.
Switching mice from a high-fat to a low-fat diet restored memory in one week, he noted.
In mice that continued on the high-fat diet, impaired object recognition remained three weeks after the onset of symptoms. But Freund knows from other studies that brain biochemistry normalizes after 10 weeks as the body appears to compensate for the diet. At that point, brain dopamine has returned to normal, and mice have become obese and developed diabetes.
“Although the mice grow out of these anxious behaviors and learning deficiencies, the study suggests to me that a high-fat diet could trigger anxiety and memory disorders in a child who is genetically or environmentally susceptible to them,” he said.
Because the animals adapt to the high-fat fare, the scientists also hypothesized that abruptly removing fat from the diet might negatively affect anxiety, learning, and memory.
The researchers had expected that the high-fat diet would stimulate inflammation, which is associated with obesity, but they saw no evidence of an inflammatory response in the brain after one or three weeks on the high-fat regimen.
Instead, they saw evidence that a high-fat diet initiates chemical responses that are similar to the ones seen in addiction, with dopamine, the chemical important to the addict’s pleasurable experiences, increasing in the brain.
(Source: news.aces.illinois.edu)
Our primitive reflexes may be more sophisticated than they appear
Supposedly ‘primitive’ reflexes may involve more sophisticated brain function than previously thought, according to researchers at Imperial College London.
The vestibular-ocular reflex (or VOR), common to most vertebrates, is what allows us to keep our eyes focused on a fixed point even while our heads are moving. Up until now, scientists had assumed this reflex was controlled by the lower brainstem, which regulates eating, sleeping and other low-level tasks.
Researchers at Imperial’s Division of Brain Sciences conducted tests to examine this reflex in left- and right-handed subjects, revealing that handedness plays a key role in the way it operates. This suggests that higher-level functions in the cortex, which govern handedness, are involved in the control of primitive reflexes such as the VOR.
The research, published in the Journal of Neuroscience, involved seating volunteers in a motorised chair which was then spun around at a speed of one revolution every four seconds. This allowed the experimenters to study the VOR by measuring the time it took for the eyes to adjust to the spinning motion. The subjects were then presented with what are known as bistable visual phenomena, optical illusions which appear to flip between two images. Famous examples include the duck which resembles a rabbit, and the cube outline which appears to come out of and go into the page simultaneously.
Scientists already know that this bistable perception is controlled by a part of the cortex which governs more complex, decision-based tasks. Because of this, researcher Qadeer Arshad and his colleagues did not expect to find any link between the two processes.
They were surprised to find that processing bistable phenomena disrupted people’s ability to stabilise their gaze, following rightward rotation in right handers and leftward rotation in left handers. Arshad said “This is the first time that anything of this kind has been shown. Up until now, the vestibular-ocular reflex was considered a low-level reflex, not even approaching higher-order brain function. Now it seems that this primitive reflex was specialised into the cortex, the part of the brain which governs our sense of direction.”
This study could help scientists understand why some people become dizzy through experiencing purely visual stimuli, such as flickering lights or busy supermarket aisles. Professor Adolfo Bronstein, a co-author on the paper, said “Most causes of dizziness start with an inner ear - or vestibular - disorder but this initial phase tends to settle quite rapidly. In some patients, however, dizziness becomes a problematic long term problem and their dizziness becomes visually induced. The experimental set-up we used would be ideally suited to help us understand how visual stimuli could lead to long-term dizziness. In fact, we have already carried out research at Imperial around using complex visual stimuli to treat patients with long-term dizziness”
(Source: www3.imperial.ac.uk)
Shedding New Light on Infant Brain Development
A new study by Columbia Engineering researchers finds that the infant brain does not control its blood flow in the same way as the adult brain. The findings, which the scientists say could change the way researchers study brain development in infants and children, are published in the February 18 Early Online edition of Proceedings of the National Academy of Sciences (PNAS).
“The control of blood flow in the brain is very important,” says Elizabeth Hillman, associate professor of biomedical engineering and of radiology, who led the research study in her Laboratory for Functional Optical Imaging at Columbia. “Not only are regionally specific increases in blood flow necessary for normal brain function, but these blood-flow increases form the basis of signals measured in fMRI, a critical imaging tool used widely in adults and children to assess brain function. Many prior fMRI studies have overlooked the possibility that the infant brain controls blood flow differently.”
“Our results are fascinating,” says Mariel Kozberg, a neurobiology MD-PhD candidate who works under Hillman and is the lead author of the PNAS paper. “We found that the immature brain does not generate localized blood-flow increases in response to stimuli. By tracking changes in blood-flow control with increasing age, we observed the brain gradually developing its ability to increase local blood flow and, by adulthood, generate a large blood-flow response.”
The study results suggest that fMRI experiments in infants and children should be carefully designed to ensure that maturation of blood-flow control can be delineated from changes in neuronal development. “On the other hand,” says Hillman, “our findings also suggest that vascular development may be an important new factor to consider in normal and abnormal brain development, so our findings could represent new markers of normal and abnormal brain development that could potentially be related to a range of neurological or even psychological conditions.”
Scans reveal intricate brain wiring
Scientists are set to release the first batch of data from a project designed to create the first map of the human brain.
The project could help shed light on why some people are naturally scientific, musical or artistic.
Some of the first images were shown at the American Association for the Advancement of Science meeting in Boston.
I found out how researchers are developing new brain imaging techniques for the project by having my own brain scanned.
Scientists at Massachusetts General Hospital are pushing brain imaging to its limit using a purpose built scanner. It is one of the most powerful scanners in the world.
The scanner’s magnets need 22MW of electricity - enough to power a nuclear submarine.
The researchers invited me to have my brain scanned. I was asked if I wanted “the 10-minute job or the 45-minute ‘full monty’” which would give one of the most detailed scans of the brain ever carried out. Only 50 such scans have ever been done.
I went for the full monty.
It was a pleasant experience enclosed in the scanner’s vast twin magnets. Powerful and rapidly changing magnetic fields were looking to see tiny particles of water travelling along the larger nerve fibres.
By following the droplets, the scientists in the adjoining cubicle are able to trace the major connections within my brain.
Obama Seeking to Boost Study of Human Brain
The Obama administration is planning a decade-long scientific effort to examine the workings of the human brain and build a comprehensive map of its activity, seeking to do for the brain what the Human Genome Project did for .
The project, which the administration has been looking to unveil as early as March, will include federal agencies, private foundations and teams of neuroscientists and nanoscientists in a concerted effort to advance the knowledge of the brain’s billions of neurons and gain greater insights into perception, actions and, ultimately, consciousness.
Scientists with the highest hopes for the project also see it as a way to develop the technology essential to understanding diseases like and , as well as to find new therapies for a variety of mental illnesses.
Moreover, the project holds the potential of paving the way for advances in artificial intelligence.
The project, which could ultimately cost billions of dollars, is expected to be part of the president’s budget proposal next month. And, four scientists and representatives of research institutions said they had participated in planning for what is being called the Brain Activity Map project.
The details are not final, and it is not clear how much federal money would be proposed or approved for the project in a time of fiscal constraint or how far the research would be able to get without significant federal financing.
In his State of the Union address, cited brain research as an example of how the government should “invest in the best ideas.”
“Every dollar we invested to map the human genome returned $140 to our economy — every dollar,” he said. “Today our scientists are mapping the human brain to unlock the answers to Alzheimer’s. They’re developing drugs to regenerate damaged organs, devising new materials to make batteries 10 times more powerful. Now is not the time to gut these job-creating investments in science and innovation.”
Blind brain receives “visual” cues for identifying object shape
A significant number of blind humans, not unlike bats and dolphins, can localize silent objects in their environment simply by making clicking sounds with their mouth and listening to the returning echoes. Some of these individuals have honed this skill to such a degree that they are not only able to localize an object, they are able to recognize the object’s size and shape – and even identify the material it is made from.
Researchers at Western University’s Brain and Mind Institute (BMI) used functional magnetic resonance imaging (fMRI) to study the brain of renowned blind echolocator Daniel Kish as he listened to recordings of his own mouth clicks and the echoes reflected back from different objects.
The results of this study, which was carried out in collaboration with colleagues based in Durham University in the U.K., the Rotman Research Institute at the Baycrest Hospital in Toronto, and World Access for the Blind, a not-for-profit organization based in California, appeared this week in the journal Neuropsychologia. In keeping with the previous research from this group, the researchers found that areas in Kish’s brain that were activated by the echoes corresponded to visual areas in the sighted brain.
But what has senior author and BMI Director Mel Goodale most excited about the new findings is that the particular areas in Kish’s brain that extract echo-based information about object shape are located in exactly the same brain regions that are activated by visual shape cues in the sighted brain.
"This work is shedding new light on just how plastic the human brain really is," says Goodale.
Lead author Stephen Arnott of Baycrest’s Rotman Research Institute explains, “This study implies that the processing of echoes for object shape in the blind brain can take advantage of the brain’s predisposition to process particular object features, such as shape, in particular brain regions – even though the sensory system conveying that information is very different.”
Kish lost both his eyes to cancer when he was only one-year old and taught himself to echolocate when he was a toddler. Interestingly, two other blind individuals who learned to echolocate much later in life do not show nearly the same level of brain activation in these ‘visual’ object areas as Kish.
(Source: communications.uwo.ca)