Neuroscience  

Using an MRI technique that is sensitive to certain byproducts of cell metabolism, for the first time for a psychiatric condition, researchers have discovered previously unrecognized differences in the brains of patients with bipolar disorder.

Using a different type of MRI imaging, researchers at the University of Iowa have discovered previously unrecognized differences in the brains of patients with bipolar disorder. In particular, the study, published in the journal Molecular Psychiatry, revealed differences in the white matter of patients' brains and in the cerebellum, an area of the brain not previously linked with the disorder. Interestingly, the cerebellar differences were not present in patients taking lithium, the most commonly used treatment for bipolar disorder.

"This imaging technique appears to be sensitive to things that just have not been imaged effectively before. So it's really providing a new picture and new insight into the composition and function of the brain."

"This imaging technique appears to be sensitive to things that just have not been imaged effectively before. So it's really providing a new picture and new insight into the composition and function of the brain [in bipolar disease]," says John Wemmie, MD, PhD, UI professor of psychiatry and senior study author.

Bipolar disorder affects about one percent of the population. Despite being relatively common, scientists do not have a good understanding of what causes this psychiatric condition, which is characterized by sudden mood shifts from normal to depressed or to an abnormally elevated or "manic" mood state.

The study examined 15 patients with bipolar disorder and 25 control subjects matched for age and gender. The bipolar patients were all in normal (euthymic) mood state during the study.

The research team imaged the participants' brains using an MRI approach known as quantitative high-resolution T1 rho mapping, which is sensitive to certain byproducts of cell metabolism, including levels of glucose and acidity in the brain. Compared to the brains of people without bipolar disorder, the researchers found that the MRI signal was elevated in the cerebral white matter and the cerebellar region of patients affected by bipolar disorder. The elevated signal may be due to either a reduction in pH or a reduction in glucose concentration -- both factors influenced by cell metabolism.

Related articles Brain Imaging Study Reveals Deeper Understanding of Schizophrenia  New Dye Helps Show Brain Structures In Incredible Detail  Personalized Brain Mapping Helps Preserves Function Following Brain Surgery

Previous research has suggested that abnormal cell metabolism may play a role in bipolar disorder. However, investigating metabolic abnormalities in the brain has been hindered by lack of a good imaging tools. Available methods are slow, low-resolution, and require researchers to identify the region of interest at the beginning of the study.

In contrast, the new imaging approach can rapidly acquire a high-resolution image of the whole brain. The study is the first time this MRI technique has been used to investigate a psychiatric disease.

One reason researchers didn't know that the cerebellum might be important in bipolar disorder, is because no one chose to look there, says Casey Johnson, PhD, UI postdoctoral researcher and first author on the study.

"Our study was essentially exploratory. We didn't know what we would find," he adds. "The majority of bipolar disorder research has found differences in the frontal region of the brain. We found focal differences in the cerebellum, which is a region that hasn't really been highlighted in the bipolar literature before."

Spurred on by the finding, Johnson and Wemmie conducted an extensive search of the scientific literature on bipolar disorder and began to find pieces of evidence that suggested that the cerebellum may function abnormally in bipolar disorder and that lithium might potentially target the cerebellum and alter glucose levels in this brain region.

"Our paper, with this new technique, starts to bring all these pieces of evidence together for the first time," Johnson says.

Wemmie hopes that the new insights provided by the T1 rho imaging might help refine understanding of the abnormalities that underlie bipolar disease and lead to better ways to diagnose and treat this problem.

While lithium can be an effective mood stabilizer for people with bipolar disorder, it causes numerous unpleasant side effects for patients.

Bipolar Disorder Infographic — Healthline

SOURCE  University of Iowa Health Care

By 33rd Square

Embed

 Neuroplasticity  

Neuroscientists have long believed that older people have less of the neural flexibility (plasticity) required to learn new things. Now, a study shows that older people learned a visual task just as well as younger ones, but the seniors who showed a strong degree of learning exhibited plasticity in a different part of the brain than younger learners did.

Awidely presumed problem of aging is that the brain becomes less flexible — less plastic — and that learning may therefore become more difficult. A new study led by Brown University researchers contradicts that notion with a finding that plasticity did occur in seniors who learned a task well, but it occurred in a different part of the brain than in younger people.

When many older subjects learned a new visual task, the researchers found, they unexpectedly showed a significantly associated change in the white matter of the brain. White matter is the the brain’s “wiring,” or axons, sheathed in a material called myelin that can make transmission of signals more efficient. Younger learners, meanwhile, showed plasticity in the cortex, where neuroscientists expected to see it.

“We think that the degree of plasticity in the cortex gets more and more limited with older people,” said Takeo Watanabe, the Fred M. Seed Professor at Brown University and a co-author of the study published in Nature Communications. “However, they keep the ability to learn, visually at least, by changing white matter structure.”

Related articles Personalized Brain Mapping Helps Preserves Function Following Brain Surgery  Brain Epigenome Found To Change Dramatically From Infancy to Adolescence  Neural Dust May Provide Brain-Machine Interface Solution

The study’s lead authors are Yuko Yotsumoto of the University of Tokyo and Li-Hung Chang of Brown University and National Yang Ming University in Taiwan. The corresponding author is Yuka Sasaki, associate professor (research) of cognitive, linguistic, and psychological sciences at Brown University.

"We think that the degree of plasticity in the cortex gets more and more limited with older people. However, they keep the ability to learn, visually at least, by changing white matter structure."

The team’s study enrolled 18 volunteers aged 65 to 80 and 21 volunteers aged 19 to 32 to learn and perform an abstract visual perception task in the lab over the course of about a week. They saw screens showing a background texture of lines oriented in a particular direction. Sometimes a small patch of the screen would quickly show lines pointing in one of two different directions against that background. Subjects simply had to push a button indicating they saw a patch with a particular orientation.

Individuals varied, but older subjects were just as likely on average as younger ones to make substantial progress in discriminating the small patch’s different texture. But the researchers weren’t just interested in whether learning occurred. They also scanned the brains of the volunteers at the beginning and the end of the week using magnetic resonance imaging, which can indicate plasticity in the cortex, and using diffusion tensor imaging, which can indicate changes in white matter.

The scans focused on the section of the brain responsible for visual learning, the early visual cortex (gray matter), and on the white matter beneath it. Moreover, the researchers strategically positioned the texture patch in the same part of the subject’s visual field. That was to ensure that a specific part of the visual cortex (and white matter beneath) that handles signals for that section of the visual field would be trained, while other sections would not.

In analyzing the scan results and the learning performance results together, the researchers found several important associations:

• -For changes in the cortex, younger learners showed significantly more than older learners. For changes in white matter, older learners showed significantly more than younger learners.
• -In volunteers of both age groups, brain changes occurred only in the sections corresponding with the specific part of the visual field where the patches occurred.

The study produced another curious finding. In looking more deeply at the association between white matter changes and learning performance in the older subjects, the researchers found that they separated into two clearly distinct groups: “good learners” and “poor learners.” In the group that learned very well (their accuracy in discriminating the patch increased by more than 20 percent), members showed a positive association between white matter changes and their improved learning. But among the “poor learner” group (which had a less than 20 percent improvement), the trend was that learning improvement decreased with greater white matter change.

The study doesn’t explain what accounted for why older subjects fell into one group or the other.

The results also don’t definitively explain why white matter plasticity would enable good learners to learn well, although improved signal transmission efficiency is one hypothesis.

But for many seniors, it may be encouraging to learn that plasticity doesn’t necessarily decline with age, it may just shift with the whitening of hair to the brain’s white matter.


SOURCE  Brown University

By 33rd Square

Embed

 Neuroscience  

For the first time, neuroscientists have systematically mapped the white matter "scaffold" of the human brain, the critical communications network that supports brain function.

For the first time, neuroscientists have systematically identified the white matter "scaffold" of the human brain, the critical communications network that supports brain function.

Their work, published in the open-source journal Frontiers in Human Neuroscience, has major implications for understanding brain injury and disease. By detailing the connections that have the greatest influence over all other connections, the researchers offer not only a landmark first map of core white matter pathways, but also show which connections may be most vulnerable to damage.

"We coined the term white matter 'scaffold' because this network defines the information architecture which supports brain function," said senior author John Darrell Van Horn of the USC Institute for Neuroimaging and Informatics and the Laboratory of Neuro Imaging at USC.

"While all connections in the brain have their importance, there are particular links which are the major players," Van Horn said.

Graphical representation of human brain connectivity scaffold.
Image Source -  USC Institute for Neuroimaging and Informatics

Using MRI data from a large sample of 110 individuals, lead author Andrei Irimia, also of the USC Institute for Neuroimaging and Informatics, and Van Horn systematically simulated the effects of damaging each white matter pathway.

Related articles Breakthrough Technique Gives Unprecedented View Inside The Brain  Brain Surgeons Find The Neurological Basis of Human Speech  Researchers Demonstrate Matrix-Style Learning

They found that the most important areas of white and gray matter don't always overlap. Gray matter is the outermost portion of the brain containing the neurons where information is processed and stored. Past research has identified the areas of gray matter that are disproportionately affected by injury.

But the current study shows that the most vulnerable white matter pathways – the core "scaffolding" – are not necessarily just the connections among the most vulnerable areas of gray matter, helping explain why seemingly small brain injuries may have such devastating effects.

"Sometimes people experience a head injury which seems severe but from which they are able to recover. On the other hand, some people have a seemingly small injury which has very serious clinical effects," says Van Horn, associate professor of neurology at the Keck School of Medicine of USC. "This research helps us to better address clinical challenges such as traumatic brain injury and to determine what makes certain white matter pathways particularly vulnerable and important."

The researchers compare their brain imaging analysis to models used for understanding social networks. To get a sense of how the brain works, Irimia and Van Horn did not focus only on the most prominent gray matter nodes – which are akin to the individuals within a social network. Nor did they merely look at how connected those nodes are.

Image Source -  USC Institute for Neuroimaging and Informatics

Rather, they also examined the strength of these white matter connections, i.e. which connections seemed to be particularly sensitive or to cause the greatest repercussions across the network when removed. Those connections which created the greatest changes form the network "scaffold."

"Just as when you remove the internet connection to your computer you won't get your email anymore, there are white matter pathways which result in large scale communication failures in the brain when damaged," Van Horn said.

When white matter pathways are damaged, brain areas served by those connections may wither or have their functions taken over by other brain regions, the researchers explain. Irimia and Van Horn's research on core white matter connections is part of a worldwide scientific effort to map the 100 billion neurons and 1,000 trillion connections in the living human brain, led by the Human Connectome Project and the Laboratory of Neuro Imaging at USC.

Irimia notes that, "these new findings on the brain's network scaffold help inform clinicians about the neurological impacts of brain diseases such as multiple sclerosis, Alzheimer's disease, as well as major brain injury. Sports organizations, the military and the US government have considerable interest in understanding brain disorders, and our work contributes to that of other scientists in this exciting era for brain research."


SOURCE  University of Southern California

By 33rd Square

Subscribe to 33rd Square

 Neuroscience  

Patients with the most common form of focal epilepsy have widespread, abnormal connections in their brains that could provide clues toward diagnosis and treatment, according to a new study.

P atients with the most common form of focal epilepsy have widespread, abnormal connections in their brains that could provide clues toward diagnosis and treatment, according to a new study published online in the journal Radiology.

Temporal lobe epilepsy is characterized by seizures emanating from the temporal lobes, which sit on each side of the brain just above the ear. Previously, experts believed that the condition was related to isolated injuries of structures within the temporal lobe, like the hippocampus. But recent research has implicated the default mode network (DMN), the set of brain regions activated during task-free introspection and deactivated during goal-directed behavior. The DMN consists of several hubs that are more active during the resting state.

To learn more, researchers performed diffusion tensor imaging, a type of MRI that tracks the movement, or diffusion, of water in the brain's white matter, the nerve fibers that transmit signals throughout the brain. The study group consisted of 24 patients with left temporal lobe epilepsy who were slated for surgery to remove the site from where their seizures emanated. The researchers compared them with 24 healthy controls using an MRI protocol dedicated to finding white matter tracts with diffusion imaging at high resolution. The data was analyzed with a new technique that identifies and quantifies structural connections in the brain.

Related articles Brain Imaging Study Reveals Deeper Understanding of Schizophrenia  Glial Cells Found To Power Neurons In The Brain  Human Memory Implants May Soon Be Tested

Patients with left temporal lobe epilepsy exhibited a decrease in long-range connectivity of 22 percent to 45 percent among areas of the DMN when compared with the healthy controls.

"Using diffusion MRI, we found alterations in the structural connectivity beyond the medial temporal lobe, especially in the default mode network," said Steven M. Stufflebeam, M.D., from the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital in Boston.

In addition to reduced long-range connectivity, the epileptic patients had an 85 percent to 270 percent increase in local connectivity within and beyond the DMN. The researchers believe this may be an adaptation to the loss of the long-range connections.

"The increase in local connections could represent a maladaptive mechanism by which overall neural connectivity is maintained despite the loss of connections through important hub areas," Dr. Stufflebeam said.

The results are supported by prior functional MRI studies that have shown decreased functional connectivity in DMN areas in temporal lobe epilepsy. Researchers are not certain if the structural changes cause the functional changes, or vice versa.

"It's probably a breakdown of myelin, which is the insulation of neurons, causing a slowdown in the propagation of information, but we don't know for sure," Dr. Stufflebeam said.

Dr. Stufflebeam and colleagues plan to continue their research, using structural and functional MRI with electroencephalography and magnetoencephalography to track diffusion changes and look at real-time brain activity.


SOURCE  MedicalXpress

By 33rd Square

Subscribe to 33rd Square