Posts tagged gray matter
Articles and news from the latest research reports.
Brain scans reveal ‘grey matter’ differences in media multitaskers
Simultaneously using mobile phones, laptops and other media devices could be changing the structure of our brains, according to new University of Sussex research.
A study published today (24 September) in PLOS ONE reveals that people who frequently use several media devices at the same time have lower grey-matter density in one particular region of the brain compared to those who use just one device occasionally.
The research supports earlier studies showing connections between high media-multitasking activity and poor attention in the face of distractions, along with emotional problems such as depression and anxiety.
But neuroscientists Kep Kee Loh and Dr Ryota Kanai point out that their study reveals a link rather than causality and that a long-term study needs to be carried out to understand whether high concurrent media usage leads to changes in the brain structure, or whether those with less-dense grey matter are more attracted to media multitasking.
The researchers at the University of Sussex’s Sackler Centre for Consciousness Science used functional magnetic resonance imaging (fMRI) to look at the brain structures of 75 adults, who had all answered a questionnaire regarding their use and consumption of media devices, including mobile phones and computers, as well as television and print media.
They found that, independent of individual personality traits, people who used a higher number of media devices concurrently also had smaller grey matter density in the part of the brain known as the anterior cingulate cortex (ACC), the region notably responsible for cognitive and emotional control functions.
Kep Kee Loh says: “Media multitasking is becoming more prevalent in our lives today and there is increasing concern about its impacts on our cognition and social-emotional well-being. Our study was the first to reveal links between media multitasking and brain structure.”
Scientists have previously demonstrated that brain structure can be altered upon prolonged exposure to novel environments and experience. The neural pathways and synapses can change based on our behaviours, environment, emotions, and can happen at the cellular level (in the case of learning and memory) or cortical re-mapping, which is how specific functions of a damaged brain region could be re-mapped to a remaining intact region.
Other studies have shown that training (such as learning to juggle, or taxi drivers learning the map of London) can increase grey-matter densities in certain parts of the brain.
“The exact mechanisms of these changes are still unclear,” says Kep Kee Loh. “Although it is conceivable that individuals with small ACC are more susceptible to multitasking situations due to weaker ability in cognitive control or socio-emotional regulation, it is equally plausible that higher levels of exposure to multitasking situations leads to structural changes in the ACC. A longitudinal study is required to unambiguously determine the direction of causation.”
(Source: sussex.ac.uk)
Grey matter matters when measuring our tolerance of risk
There is a link between our brain structure and our tolerance of risk, new research suggests.
Dr Agnieszka Tymula, an economist at the University of Sydney, is one of the lead authors of a new study that identifies what might be considered the first stable ‘biomarker’ for financial risk-attitudes.
Using a whole-brain analysis, Dr Tymula and international collaborators found that the grey matter volume of a region in the right posterior parietal cortex was significantly predictive of individual risk attitudes. Men and women with higher grey matter volume in this region exhibited less risk aversion.
"Individual risk attitudes are correlated with the grey matter volume in the posterior parietal cortex suggesting existence of an anatomical biomarker for financial risk-attitude," said Dr Tymula.
This means tolerance of risk “could potentially be measured in billions of existing medical brain scans.”
But she has cautioned against making a causal link between brain structure and behaviour. More research will be needed to establish whether structural changes in the brain lead to changes in risk attitude or whether that individual’s risky choices alter his or her brain structure - or both.
"The findings fit nicely with our previous findings on risk attitude and ageing. In our Proceedings of the National Academy of Sciences 2013 paper we found that as people age they become more risk averse,” she said.
"From other work we know that cortex thins substantially as we age. It is possible that changes in risk attitude over lifespan are caused by thinning of the cortex."
The findings are published in the September 10 issue of The Journal of Neuroscience.
(Image caption: Example axial sections of a three-dimensional MPF map (A) obtained from a 63-year old woman with SPMS disease course and results of brain tissue segmentation (B-D). Segmentation masks corresponding to white matter (WM) (B), gray matter (GM) (C), and lesi)
MRI Shows Gray Matter Myelin Loss Strongly Related to MS Disability
People with multiple sclerosis (MS) lose myelin in the gray matter of their brains and the loss is closely correlated with the severity of the disease, according to a new magnetic resonance imaging (MRI) study. Researchers said the findings could have important applications in clinical trials and treatment monitoring. The study appears online in the journal Radiology.
Loss of myelin, the fatty protective sheath around nerve fibers, is a characteristic of MS, an inflammatory disease of the central nervous system that can lead to a variety of serious neurological symptoms and disability. MS is typically considered a disease of the brain’s signal-conducting white matter, where myelin is most abundant, but myelin is also present in smaller amounts in gray matter, the brain’s information processing center that is made up primarily of nerve cell bodies. Though the myelin content in gray matter is small, it is still extremely important to proper function, as it enables protection of thin nerve fibers connecting neighboring areas of the brain cortex, according to Vasily L. Yarnykh, Ph.D., associate professor in the Department of Radiology at University of Washington in Seattle.
“The fact that MS patients lose myelin not only in white but also in gray matter has been proven by earlier post-mortem pathological studies,” he said. “However, the clinical significance of the myelin loss, or demyelination, in gray matter has not been established because of the absence of appropriate imaging methods.”
To learn more about associations between MS and demyelination in both white and gray matter, Dr. Yarnykh and colleagues used a refined MRI technique that provides information on the content of biological macromolecules – molecules present in tissues and composed of a large number of atoms, such as proteins, lipids and carbohydrates. The new method, known as macromolecular proton fraction (MPF) mapping, has been hampered in the past because of the length of time required for data collection, but improvements now allow much faster generation of whole-brain maps that reflect the macromolecular content in tissues.
“The method utilizes a standard MRI scanner and doesn’t require any special hardware—only some software modifications,” Dr. Yarnykh said. “MPF mapping allows quantitative assessment of microscopic demyelination in brain tissues that look normal on clinical images, and is the only existing method able to evaluate the myelin content in gray matter.”
The researchers looked at 30 MS patients, including 18 with relapsing-remitting MS (RRMS), the most common type of MS initially diagnosed, and 12 with the more advanced type of disease known as secondary progressive MS (SPMS). Fourteen healthy control participants were also included in the study. Each participant underwent MRI on a 3-Tesla imager, and the researchers reconstructed 3-D whole-brain MPF maps to look at normal-appearing white matter, gray matter and MS lesions. The researchers further compared the results of their imaging technique with clinical tests characterizing neurological dysfunction in MS patients.
The results showed that MPF was significantly lower in both white and gray matter in RRMS patients compared with healthy controls, and was also significantly reduced in both normal-appearing brain tissues and lesions of SPMS patients compared to RRMS patients with the largest relative decrease in gray matter. MPF in brain tissues of MS patients significantly correlated with clinical disability and the strongest associations were found for gray matter.
“The major finding of the study is that the loss of myelin in gray matter caused by MS in its relative amount is comparable to or even larger than that in white matter,” said Dr. Yarnykh. “Furthermore, gray matter demyelination is much more advanced in patients with secondary-progressive MS, and it is very strongly related to patients’ disability. As such, we believe that information about gray matter myelin damage in MS is of primary clinical relevance.”
The improved technique has potentially important applications for MS treatments targeted to protect and restore myelin.
“First, this method may provide an objective measure of the disease progression and treatment success in clinical trials,” Dr. Yarnykh said. “And second, assessment of both gray and white matter damage with this method may become an individual patient management tool in the future.”
Dr. Yarnykh and colleagues are currently conducting additional research on the new method with the support of the National Multiple Sclerosis Society and the National Institutes of Health.
“This study was done on the participants at a single point in time,” he said. “Now we want to compare MS patients with control participants to see how myelin content will evolve over time. We further plan to extend our method to the spinal cord imaging and test whether the combined assessment of demyelination in the brain and spinal cord could better explain disability progression as compared to brain demyelination alone.”
Neural Anatomy of Primary Visual Cortex Limits Visual Working Memory
Despite the immense processing power of the human brain, working memory storage is severely limited, and the neuroanatomical basis of these limitations has remained elusive. Here, we show that the stable storage limits of visual working memory for over 9 s are bound by the precise gray matter volume of primary visual cortex (V1), defined by fMRI retinotopic mapping. Individuals with a bigger V1 tended to have greater visual working memory storage. This relationship was present independently for both surface size and thickness of V1 but absent in V2, V3 and for non-visual working memory measures. Additional whole-brain analyses confirmed the specificity of the relationship to V1. Our findings indicate that the size of primary visual cortex plays a critical role in limiting what we can hold in mind, acting like a gatekeeper in constraining the richness of working mental function.
(Image: Shutterstock)
Bioengineers Create Functional 3D Brain-like Tissue
Bioengineers have created three-dimensional brain-like tissue that functions like and has structural features similar to tissue in the rat brain and that can be kept alive in the lab for more than two months.
As a first demonstration of its potential, researchers used the brain-like tissue to study chemical and electrical changes that occur immediately following traumatic brain injury and, in a separate experiment, changes that occur in response to a drug. The tissue could provide a superior model for studying normal brain function as well as injury and disease, and could assist in the development of new treatments for brain dysfunction.
The brain-like tissue was developed at the Tissue Engineering Resource Center at Tufts University, Boston, which is funded by the National Institute of Biomedical Imaging and Bioengineering (NIBIB) to establish innovative biomaterials and tissue engineering models. David Kaplan, Ph.D., Stern Family Professor of Engineering at Tufts University is director of the center and led the research efforts to develop the tissue.
Currently, scientists grow neurons in petri dishes to study their behavior in a controllable environment. Yet neurons grown in two dimensions are unable to replicate the complex structural organization of brain tissue, which consists of segregated regions of grey and white matter. In the brain, grey matter is comprised primarily of neuron cell bodies, while white matter is made up of bundles of axons, which are the projections neurons send out to connect with one another. Because brain injuries and diseases often affect these areas differently, models are needed that exhibit grey and white matter compartmentalization.
Recently, tissue engineers have attempted to grow neurons in 3D gel environments, where they can freely establish connections in all directions. Yet these gel-based tissue models don’t live long and fail to yield robust, tissue-level function. This is because the extracellular environment is a complex matrix in which local signals establish different neighborhoods that encourage distinct cell growth and/or development and function. Simply providing the space for neurons to grow in three dimensions is not sufficient.
Now, in the Aug. 11th early online edition of the journal Proceedings of the National Academy of Sciences, a group of bioengineers report that they have successfully created functional 3D brain-like tissue that exhibits grey-white matter compartmentalization and can survive in the lab for more than two months.
“This work is an exceptional feat,” said Rosemarie Hunziker, Ph.D., program director of Tissue Engineering at NIBIB. “It combines a deep understand of brain physiology with a large and growing suite of bioengineering tools to create an environment that is both necessary and sufficient to mimic brain function.”
The key to generating the brain-like tissue was the creation of a novel composite structure that consisted of two biomaterials with different physical properties: a spongy scaffold made out of silk protein and a softer, collagen-based gel. The scaffold served as a structure onto which neurons could anchor themselves, and the gel encouraged axons to grow through it.
To achieve grey-white matter compartmentalization, the researchers cut the spongy scaffold into a donut shape and populated it with rat neurons. They then filled the middle of the donut with the collagen-based gel, which subsequently permeated the scaffold. In just a few days, the neurons formed functional networks around the pores of the scaffold, and sent longer axon projections through the center gel to connect with neurons on the opposite side of the donut. The result was a distinct white matter region (containing mostly cellular projections, the axons) formed in the center of the donut that was separate from the surrounding grey matter (where the cell bodies were concentrated).
Over a period of several weeks, the researchers conducted experiments to determine the health and function of the neurons growing in their 3D brain-like tissue and to compare them with neurons grown in a collagen gel-only environment or in a 2D dish. The researchers found that the neurons in the 3D brain-like tissues had higher expression of genes involved in neuron growth and function. In addition, the neurons grown in the 3D brain-like tissue maintained stable metabolic activity for up to five weeks, while the health of neurons grown in the gel-only environment began to deteriorate within 24 hours. In regard to function, neurons in the 3D brain-like tissue exhibited electrical activity and responsiveness that mimic signals seen in the intact brain, including a typical electrophysiological response pattern to a neurotoxin.
Because the 3D brain-like tissue displays physical properties similar to rodent brain tissue, the researchers sought to determine whether they could use it to study traumatic brain injury. To simulate a traumatic brain injury, a weight was dropped onto the brain-like tissue from varying heights. The researchers then recorded changes in the neurons’ electrical and chemical activity, which proved similar to what is ordinarily observed in animal studies of traumatic brain injury.
Kaplan says the ability to study traumatic injury in a tissue model offers advantages over animal studies, in which measurements are delayed while the brain is being dissected and prepared for experiments. “With the system we have, you can essentially track the tissue response to traumatic brain injury in real time,” said Kaplan. “Most importantly, you can also start to track repair and what happens over longer periods of time.”
Kaplan emphasized the importance of the brain-like tissue’s longevity for studying other brain disorders. “The fact that we can maintain this tissue for months in the lab means we can start to look at neurological diseases in ways that you can’t otherwise because you need long timeframes to study some of the key brain diseases,” he said.
Hunziker added, “Good models enable solid hypotheses that can be thoroughly tested. The hope is that use of this model could lead to an acceleration of therapies for brain dysfunction as well as offer a better way to study normal brain physiology.”
Kaplan and his team are looking into how they can make their tissue model more brain-like. In this recent report, the researchers demonstrated that they can modify their donut scaffold so that it consists of six concentric rings, each able to be populated with different types of neurons. Such an arrangement would mimic the six layers of the human brain cortex, in which different types of neurons exist.
As part of the funding agreement for the Tissue Engineering Resource Center, NIBIB requires that new technologies generated at the center be shared with the greater biomedical research community.
“We look forward to building collaborations with other labs that want to build on this tissue model,” said Kaplan.
Eating Baked or Broiled Fish Weekly Boosts Brain Health
Eating baked or broiled fish once a week is good for the brain, regardless of how much omega-3 fatty acid it contains, according to researchers at the University of Pittsburgh School of Medicine. The findings, published online recently in the American Journal of Preventive Medicine, add to growing evidence that lifestyle factors contribute to brain health later in life.
Scientists estimate that more than 80 million people will have dementia by 2040, which could become a substantial burden to families and drive up health care costs, noted senior investigator James T. Becker, Ph.D., professor of psychiatry, Pitt School of Medicine. Some studies have predicted that lifestyle changes such as a reduction in rates of physical inactivity, smoking and obesity could lead to fewer cases of Alzheimer’s disease and other conditions of cognitive impairment in the elderly. The anti-oxidant effect of omega-3 fatty acids, which are found in high amounts in fish, seeds and nuts, and certain oils, also have been associated with improved health, particularly brain health.
“Our study shows that people who ate a diet that included baked or broiled, but not fried, fish have larger brain volumes in regions associated with memory and cognition,” Dr. Becker said. “We did not find a relationship between omega-3 levels and these brain changes, which surprised us a little. It led us to conclude that we were tapping into a more general set of lifestyle factors that were affecting brain health of which diet is just one part.”
Lead investigator Cyrus Raji, M.D., Ph.D., who now is in radiology residency training at UCLA, and the research team analyzed data from 260 people who provided information on their dietary intake, had high-resolution brain MRI scans, and were cognitively normal at two time points during their participation in the Cardiovascular Health Study (CHS), a 10-year multicenter effort that began in 1989 to identify risk factors for heart disease in people over 65.
“The subset of CHS participants answered questionnaires about their eating habits, such as how much fish did they eat and how was it prepared,” Dr. Raji said. “Baked or broiled fish contains higher levels of omega-3s than fried fish because the fatty acids are destroyed in the high heat of frying, so we took that into consideration when we examined their brain scans.”
People who ate baked or broiled fish at least once a week had greater grey matter brain volumes in areas of the brain responsible for memory (4.3 percent) and cognition (14 percent) and were more likely to have a college education than those who didn’t eat fish regularly, the researchers found. But no association was found between the brain differences and blood levels of omega-3s.
“This suggests that lifestyle factors, in this case eating fish, rather than biological factors contribute to structural changes in the brain,” Dr. Becker noted. “A confluence of lifestyle factors likely are responsible for better brain health, and this reserve might prevent or delay cognitive problems that can develop later in life.”
Creatures of habit: disorders of compulsivity share common pattern and brain structure
In a study published in the journal Molecular Psychiatry and primarily funded by the Wellcome Trust, researchers show that people who are affected by disorders of compulsivity have lower grey matter volumes (in other words, fewer nerve cells) in the brain regions involved in keeping track of goals and rewards.
In our daily lives, we make decisions based either on habit or aimed at achieving a specific goal. For example, when driving home from work, we tend to follow habitual choices – our ‘autopilot’ mode – as we know the route well; however, if we move to a nearby street, we will initially follow a ‘goal-directed’ choice to find our way home – unless we slip into autopilot and revert to driving back to our old home. However, we cannot always control the decision-making process and make repeat choices even when we know they are bad for us – in many cases this will be relatively benign, such as being tempted by a cake whilst slimming, but extreme cases it can lead to disorders of compulsivity.
In order to understand what happens when our decision-making processes malfunction, a team of researchers led by the Department of Psychiatry at the University of Cambridge compared almost 150 individuals with disorders including methamphetamine dependence, obesity with binge eating and obsessive compulsive disorder, comparing them with healthy volunteers of the same age and gender.
Study participants first took part in a computerised task to test their ability to make choices aimed a receiving a reward over and above making compulsive choices. In a second study, the researchers compared brain scans taken using magnetic resonance imaging (MRI) in healthy individuals and a subset of obese individuals with or without binge eating disorder (a subtype of obesity in which the person binge eats large amounts of food rapidly).
The researchers demonstrated that all of the disorders were connected by a shift away from goal-directed behaviours towards automatic habitual choices. The MRI scans showed that obese subjects with binge eating disorder have lower grey matter volumes – a measure of the number of neurons – in the orbitofrontal cortex and striatum of the brain compared to those who do not binge eat; these brain regions are involved in keeping track of goals and rewards. Even in healthy volunteers, lower grey matter volumes were associated with a shift towards more habitual choices.
Dr Valerie Voon, principal investigator of the study, says: “Seemingly diverse choices – drug taking, eating quickly despite weight gain, and compulsive cleaning or checking – have an underlying common thread: rather that a person making a choice based on what they think will happen, their choice is automatic or habitual.
“Compulsive disorders can have a profoundly disabling effect of individuals. Now that we know what is going wrong with their decision making, we can look at developing treatments, for example using psychotherapy focused on forward planning or interventions such as medication which target the shift towards habitual choices.”
Does porn affect the brain? Scientists urge more study
Researchers found less grey matter in the brains of men who watched large amounts of sexually explicit material, according to a new study.
The research, which appeared Wednesday in the journal JAMA Psychiatry, could not determine if porn actually caused the brain to shrink however, and the authors called for additional study on the topic.
"Future studies should investigate the effects of pornography longitudinally or expose naive participants to pornography and investigate the causal effects over time," said researchers at the Max Planck Institute for Human Development in Berlin, Germany.
In Old Age, Lack of Emotion and Interest May Signal Your Brain Is Shrinking
Older people who have apathy but not depression may have smaller brain volumes than those without apathy, according to a new study published in the April 16, 2014, online issue of Neurology®, the medical journal of the American Academy of Neurology. Apathy is a lack of interest or emotion.
“Just as signs of memory loss may signal brain changes related to brain disease, apathy may indicate underlying changes,” said Lenore J. Launer, PhD, with the National Institute on Aging at the National Institutes of Health (NIH) in Bethesda, MD, and a member of the American Academy of Neurology. “Apathy symptoms are common in older people without dementia. And the fact that participants in our study had apathy without depression should turn our attention to how apathy alone could indicate brain disease.”
Launer’s team used brain volume as a measure of accelerated brain aging. Brain volume losses occur during normal aging, but in this study, larger amounts of brain volume loss could indicate brain diseases.
For the study, 4,354 people without dementia and with an average age of 76 underwent an MRI scan. They were also asked questions that measure apathy symptoms, which include lack of interest, lack of emotion, dropping activities and interests, preferring to stay at home and having a lack of energy.
The study found that people with two or more apathy symptoms had 1.4 percent smaller gray matter volume and 1.6 percent less white matter volume compared to those who had less than two symptoms of apathy. Excluding people with depression symptoms did not change the results.
Gray matter is where learning takes place and memories are stored in the brain. White matter acts as the communication cables that connect different parts of the brain.
“If these findings are confirmed, identifying people with apathy earlier may be one way to target an at-risk group,” Launer said.
Research sheds new light on impact of diabetes on the brain
The new findings published in the Diabetes Care journal reveal the extent of damage patients suffering with the disease can endure in areas of the brain called ‘grey matter’ – a key component of the central nervous system which is involved in touch and pain sensory perception.
During the study, which involved patients with Type 1 and Type 2 diabetes, researchers used recent advances in ground breaking brain imaging and analyses methods to take detailed nerve assessments of the brain using magnetic resonance imaging (MRI) techniques.
This revealed that the volume of certain brain regions in people with diabetic neuropathy was significantly lower compared to those without the disease. Previous studies have shown that the impact of the disease on the brain is limited and isolated to outside areas of the brain considered to be peripheral to core functions in the body.
The breakthrough could pave the way for better assessment and monitoring of the disease, which affects around a third of people with diabetes. This, in turn, could lead to better treatments for sufferers in the future.