Posts tagged brain
Articles and news from the latest research reports.
Medical illustrators and neurological imaging experts at Johns Hopkins have figured out how night-hunting owls can almost fully rotate their heads - by as much as 270 degrees in either direction - without damaging the delicate blood vessels in their necks and heads, and without cutting off blood supply to their brains.
In what may be the first use of angiography, CT scans and medical illustrations to examine the anatomy of a dozen of the big-eyed birds, the Johns Hopkins team, led by medical illustrator Fabian de Kok-Mercado, M.A., a recent graduate student in the Department of Art as Applied to Medicine, found four major biological adaptations designed to prevent injury from rotational head movements. The variations are all to the strigid animals’ bone structure and vascular network needed to support its top-heavy head. The team’s findings are acknowledged in the Feb.1 issue of the journal Science, as first-place prize winners in the posters and graphics category of the National Science Foundation’s 2012 International Science & Engineering Visualization Challenge.
Genome-wide Atlas of Gene Enhancers in the Brain On-line
Future research into the underlying causes of neurological disorders such as autism, epilepsy and schizophrenia, should greatly benefit from a first-of-its-kind atlas of gene-enhancers in the cerebrum (telencephalon). This new atlas, developed by a team led by researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) is a publicly accessible Web-based collection of data that identifies and locates thousands of gene-regulating elements in a region of the brain that is of critical importance for cognition, motor functions and emotion.
“Understanding how the brain develops and functions, and how it malfunctions in neurological disorders, remains one of the most daunting challenges in contemporary science,” says Axel Visel, a geneticist with Berkeley Lab’s Genomics Division. “We’ve created a genome-wide digital atlas of gene enhancers in the human brain – the switches that tell genes when and where they need to be switched on or off. This enhancer atlas will enable other scientists to study in more detail how individual genes are regulated during development of the brain, and how genetic mutations may impact human neurological disorders.”
Visel is the corresponding author of a paper in the journal Cell that describes this work. The paper is titled “A High-Resolution Enhancer Atlas of the Developing Telencephalon.”
In-brain monitoring shows memory network
Working with patients with electrodes implanted in their brains, researchers at the University of California, Davis, and The University of Texas Health Science Center at Houston (UTHealth) have shown for the first time that areas of the brain work together at the same time to recall memories. The unique approach promises new insights into how we remember details of time and place.
"Previous work has focused on one region of the brain at a time," said Arne Ekstrom, assistant professor at the UC Davis Center for Neuroscience. "Our results show that memory recall involves simultaneous activity across brain regions." Ekstrom is senior author of a paper describing the work published Jan. 27 in the journal Nature Neuroscience.
Ekstrom and UC Davis graduate student Andrew Watrous worked with patients being treated for a severe seizure condition by neurosurgeon Dr. Nitin Tandon and his UTHealth colleagues.
To pinpoint the origin of the seizures in these patients, Tandon and his team place electrodes on the patient’s brain inside the skull. The electrodes remain in place for one to two weeks for monitoring.
Six such patients volunteered for Ekstrom and Watrous’ study while the electrodes were in place. Using a laptop computer, the patients learned to navigate a route through a virtual streetscape, picking up passengers and taking them to specific places. Later, they were asked to recall the routes from memory.
Correct memory recall was associated with increased activity across multiple connected brain regions at the same time, Ekstrom said, rather than activity in one region followed by another.
However, the analysis did show that the medial temporal lobe is an important hub of the memory network, confirming earlier studies, he said.
Intriguingly, memories of time and of place were associated with different frequencies of brain activity across the network. For example, recalling, “What shop is next to the donut shop?” set off a different frequency of activity from recalling “Where was I at 11 a.m.?”
Using different frequencies could explain how the brain codes and recalls elements of past events such as time and location at the same time, Ekstrom said.
"Just as cell phones and wireless devices work at different radio frequencies for different information, the brain resonates at different frequencies for spatial and temporal information," he said.
The researchers hope to explore further how the brain codes information in future work.
The neuroscientists analyzed their results with graph theory, a new technique that is being used for studying networks, ranging from social media connections to airline schedules.
"Previously, we didn’t have enough data from different brain regions to use graph theory. This combination of multiple readings during memory retrieval and graph theory is unique," Ekstrom said.
Placing electrodes inside the skull provides clearer resolution of electrical signals than external electrodes, making the data invaluable for the study of cognitive functions, Tandon said. “This work has yielded important insights into the normal mechanisms underpinning recall, and provides us with a framework for the study of memory dysfunction in the future.”
Research Institute Study Shows How Brain Cells Shape Temperature Preferences
While the wooly musk ox may like it cold, fruit flies definitely do not. They like it hot, or at least warm. In fact, their preferred optimum temperature is very similar to that of humans—76 degrees F.
Scientists have known that a type of brain cell circuit helps regulate a variety of innate and learned behavior in animals, including their temperature preferences. What has been a mystery is whether or not this behavior stems from a specific set of neurons (brain cells) or overlapping sets.
Now, a new study from The Scripps Research Institute (TSRI) shows that a complex set of overlapping neuronal circuits work in concert to drive temperature preferences in the fruit fly Drosophila by affecting a single target, a heavy bundle of neurons within the fly brain known as the mushroom body. These nerve bundles, which get their name from their bulbous shape, play critical roles in learning and memory.
The study, published in the January 30, 2013 edition of the Journal of Neuroscience, shows that dopaminergic circuits—brain cells that synthesize dopamine, a common neurotransmitter—within the mushroom body do not encode a single signal, but rather perform a more complex computation of environmental conditions.
“We found that dopamine neurons process multiple inputs to generate multiple outputs—the same set of nerves process sensory information and reward-avoidance learning,” said TSRI Assistant Professor Seth Tomchik. “This discovery helps lay the groundwork to better understand how information is processed in the brain. A similar set of neurons is involved in behavior preferences in humans—from basic rewards to more complex learning and memory.”
Using imaging techniques that allow scientists to visualize neuron activity in real time, the study illuminated the response of dopaminergic neurons to changes in temperature. The behavioral roles were then examined by silencing various subsets of these neurons. Flies were tested using a temperature gradient plate; the flies moved from one place to another to express their temperature preferences.
As it turns out, genetic silencing of dopaminergic neurons innervating the mushroom body substantially reduces cold avoidance behavior. “If you give the fly a choice, it will pick San Diego weather every time,” Tomchik said, “but if you shut down those nerves, they suddenly don’t mind being in Minnesota.”
The study also showed dopaminergic neurons respond to cooling with sudden a burst of activity at the onset of a drop in temperature, before settling down to a lower steady-state level. This initial burst of dopamine could function to increase neuronal plasticity—the ability to adapt—during periods of environmental change when the organism needs to acquire new associative memories or update previous associations with temperature changes.
(Image: ALAMY)
In the 19th century, a speechless patient wasted away in the Bicetre Hospital in France for 21 years. He was known as ‘Tan’ for the only word he could say, and for 150 years, his identity has remained a mystery. In 1861, as Tan lay dying, the famous physician Paul Broca encountered the patient. When the ill-fated patient died, Broca autopsied his brain. Broca noticed a lesion in a part of the brain tucked up behind the eyes. He concluded that the brain region was responsible for language processing. But despite Tan becoming one of the most famous medical patients in history, he was never identified until now.
A 2007 study in the journal Brain revealed the extent of the lesion using MRI imaging. A recent study identified the patient as a Monsieur Louis Leborgne, a craftsman who had suffered from epilepsy his whole life.
Tests conducted on Israel’s Ariel Sharon reveal significant brain activity
A team of American and Israeli brain scientists tested former Israeli Prime Minister Ariel Sharon to assess his brain responses, using functional magnetic resonance imaging (fMRI). Surprisingly, Sharon showed significant brain activity.
The team consisted of Martin Monti, an assistant professor of psychology and neurosurgery at UCLA, professors Alon Friedman, Galia Avidan and Tzvi Ganel of the Zlotowski Center for Neuroscience at Israel’s Ben-Gurion University of the Negev, and Dr. Ilan Shelef, head of medical imaging at Israel’s Soroka University Medical Center.
The 84-year-old Sharon, presumed to be in a vegetative state since suffering a brain hemorrhage in 2006, was scanned last week to assess the extent and quality of his brain processing, using methods recently developed by Monti and his colleagues. The test lasted approximately two hours.
The scientists showed Sharon pictures of his family, had him listen to his son’s voice and used tactile stimulation to assess the extent to which his brain responded to external stimuli.
To their surprise, significant brain activity was observed in each test, in specific brain regions, indicating appropriate processing of these stimulations, Monti said.
The scientists conducted three tests to assess Sharon’s level of consciousness. They asked him to imagine he was hitting a tennis ball and to imagine he was walking through the rooms of his home. They also showed him a photograph of a face superimposed on a photo of a house, asking him to focus first on the face and then on the house. The scientists found encouraging, but subtle, signs of consciousness.
"Information from the external world is being transferred to the appropriate parts of Mr. Sharon’s brain. However, the evidence does not as clearly indicate whether Mr. Sharon is consciously perceiving this information," Monti said. "We found faint brain activity indicating that he was complying with the tasks. He may be minimally conscious, but the results were weak and should be interpreted with caution."
Tzvi Ganel, who initiated the project, stressed that Sharon’s family wished to employ these new techniques not only for the benefit of the former prime minister but also for other families in a similar situation.
When food porn holds no allure: the science behind satiety
New research from the University of British Columbia is shedding light on why enticing pictures of food affect us less when we’re full.
“We’ve known that insulin plays a role in telling us we’re satiated after eating, but the mechanism by which this happens is unclear,” says Stephanie Borgland, an assistant professor in UBC’s Dept. of Anesthesiology, Pharmacology and Therapeutics and the study’s senior author.
In the new study published online this week in Nature Neuroscience, Borgland and colleagues found that insulin – prompted by a sweetened, high-fat meal – affects the ventral tegmental area (VTA) of the brain, which is responsible for reward-seeking behaviour. When insulin was applied to the VTA in mice, they no longer gravitated towards environments where food had been offered.
“Insulin dulls the synapses in this region of the brain and decreases our interest in seeking out food,” says Borgland, “which in turn causes us to pay less attention to food-related cues.”
“There has been a lot of discussion around the environmental factors of the obesity epidemic,” Borgland adds, pointing to fast food advertising bans in Quebec, Norway, the U.K., Greece and Sweden. “This study helps explain why pictures or other cues of food affect us less when we’re satiated – and may help inform strategies to reduce environmental triggers of overeating.”
The VTA has also been shown to be associated with addictive behaviours, including illicit drug use. Borgland says better understanding of the mechanism in this region of the brain could, in the long run, inform diagnosis and treatment.
(Image: Shutterstock)
Mediterranean diet may not protect brain
Hopes that a Mediterranean diet would be as good for the head as it is for the heart may have been dampened by a French study that found little benefit for aging brains from the diet rich in fruit, vegetables, whole grains, nuts, wine and olive oil.
The study, published in the American Journal of Clinical Nutrition, looked at the participants’ dietary patterns in middle age and measured their cognitive performance at around age 65, but found no connection between Mediterranean eating and mental performance.
"Our study does not support the hypothesis of a significant neuroprotective effect of a (Mediterranean diet) on cognitive function," writes study leader Emmanuelle Kesse-Guyot at the nutritional epidemiology research centre of the French national health research agency INSERM.
It’s been suggested that the “good” fats in the Mediterranean diet might benefit the brain directly, or that low saturated fats and high fiber in the diet could help stave off cognitive decline indirectly by keeping blood vessels healthy.
Previous research has seemed to uphold that premise.
One large study in the US Midwest, for example, found that people in their 60s and older who ate a mostly Mediterranean diet were less prone to mental decline as they aged. Another study of residents of Manhattan linked a Mediterranean-style diet to a 40 per cent lower risk of Alzheimer’s disease.
No significant difference
Researchers in the French study used data on 3083 people who were followed from the mid-1990s, when they were at least 45 years old.
At the beginning of the study, participants recorded what they ate over one 24-hour period every two months, for a total of six dietary record samples per year. Then, between 2007 and 2009 when the participants were about 65 years old, their memory and other mental abilities were measured.
Researchers then separated participants into three categories depending on how closely they adhered to a Mediterranean-style diet, and compared their mental ability test scores.
Overall, they found that people who ate a diet closest to the Mediterranean ideal performed about the same as those who ate a non-restricted diet.
Associate Professor Nikos Scarmeas, of New York’s Columbia University Medical Center, was not involved with the study but has researched the effects of food on brain health. He says it’s important to note that the new study had some limitations.
For instance, researchers only tested the participants’ mental abilities once, making it impossible to track whether they got better or worse over time, adds Scarmeas.
"We don’t have the strong evidence to go and tell people, ‘Listen, if you follow this diet, it will improve cognition’," he says.
(Image: mediterraneandiet.com)
BrainBow is a technique where cells are made to express several fluorescent proteins, in essentially random amounts. The randomness derives from feedback loops in gene expression. Mixing of fluorescence wavelengths yields a remarkable colour contrast on the single-neuron level.
The method was originally developed by Jeff W. Lichtman and Joshua R. Sanes at the Department of Neurobiology, Harvard Medical School.
Read more about BrainBow on Wikipedia or an introduction at the Harvard Gazette.
Lightning May Trigger Migraine Headaches
Migraine sufferers know that a variety of influences—everything from stress to hunger to a shift in the weather—can trigger a dreaded headache. A new study published in the journal Cephalalgia, though, suggests that another migraine trigger could be an unexpected atmospheric condition—a bolt of lightning.
As part of the study, Geoffrey Martin of the University of Cincinnati and colleagues from elsewhere asked 90 chronic migraine sufferers in Ohio and Missouri to keep detailed daily diaries documenting when they experienced headaches for three to six months. Afterward, they looked back over this period and analyzed how well the occurrence of headaches correlated with lightning strikes within 25 miles of the participants’ houses, along with other weather factors such as temperature and barometric pressure.
Their analysis found that there was a 28 precent increased chance of a migraine and a 31 precent chance of a non-migraine (i.e. less severe) headache on days when lightning struck nearby. Since lightning usually occurs during thunderstorms, which bring a host of other weather events—notable changes in barometric pressure—they used mathematical models to parse the related factors and found that even in the absence of other thunderstorm-related elements, lightning alone caused a 19 percent increased chance of headaches.
Despite these results, it’s probably a bit premature to argue that lightning is a definitive trigger of migraines. For one, a number of previous studies have explored the links between weather and migraine headaches, and the results have been unclear. Some have suggested that high pressure increases the risk of headaches, while others have indicated that low pressure increases the risk as well. Other previous studies, in fact, have failed to find a link between migraines and lightening, in particular.