Posts Tagged Magnetic resonance imaging

Alcoholism Affects Men’s and Women’s Brains Differently


Alcoholism Affects Men's and Women's Brains DifferentlyNew research has demonstrated that the effects on white matter brain volume from long-term alcohol abuse are different for men and women.

Researchers from Boston University School of Medicine (BUSM) and Veterans Affairs (VA) Boston Healthcare System also suggest that when they stop drinking, women recover their white matter brain volume more quickly than men.

Previous research has linked alcoholism with white matter reduction, according to the researchers, who explain that white matter forms the connections between neurons, allowing communication between different areas of the brain.

In this latest study, a research team, led by Susan Mosher Ruiz, Ph.D., a postdoctoral research scientist in the Laboratory for Neuropsychology at BUSM and research scientist at the VA Boston Healthcare System, and Marlene Oscar Berman, Ph.D., professor of psychiatry, neurology and anatomy and neurobiology at BUSM and research career scientist at the VA Boston Healthcare System, employed structural magnetic resonance imaging (MRI) to determine the effects of drinking history and gender on white matter volume.

They examined brain images from 42 abstinent alcoholic men and women who drank heavily for more than five years and 42 nonalcoholic men and women. The researchers found that a greater number of years of alcohol abuse was associated with smaller white matter volumes in the alcoholic men and women. In the men, the decrease was observed in the corpus callosum, while in women this effect was observed in cortical white matter regions.

“We believe that many of the cognitive and emotional deficits observed in people with chronic alcoholism, including memory problems and flat affect, are related to disconnections that result from a loss of white matter,” said Mosher Ruiz.

The researchers also found that the number of daily drinks had a strong impact on alcoholic women, with the volume loss 1.5 to 2 percent for each additional drink. Additionally, there was an 8 to 10 percent increase in the size of the brain ventricles, which are areas filled with cerebrospinal fluid (CSF) that play a protective role in the brain. When white matter dies, CSF produced in the ventricles fills the ventricular space.

The researchers also found that in men, white matter brain volume in the corpus callosum recovered at a rate of 1 percent per year for each year of abstinence. For people who abstained less than a year, the researchers found evidence of increased white matter volume and decreased ventricular volume in women, but not in men. However, for people in recovery for more than a year, those signs of recovery disappeared in women and became apparent in men.

“These findings preliminarily suggest that restoration and recovery of the brain’s white matter among alcoholics occurs later in abstinence for men than for women,” said Mosher Ruiz. “We hope that additional research in this area can help lead to improved treatment methods that include educating both alcoholic men and women about the harmful effects of excessive drinking and the potential for recovery with sustained abstinence.”

The research was published online in Alcoholism: Clinical and Experimental Research.

Source: Boston University Medical Center

Brain scan photo by shutterstock.

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Brain Abnormalities in Schizophrenia Due to Disease, Not Genetics


Brain Abnormalities in Schizophrenia Due to Disease, Not GeneticsThe brain differences found in people with schizophrenia are mainly the result of the disease itself or its treatment, as opposed to being caused by genetic factors, according to a Dutch study.

Schizophrenia is a mental disorder that significantly affects cognition and usually contributes to chronic problems with behavior and emotion. Along with a breakdown of thought processes, the disorder is also characterized by poor emotional responsiveness, paranoia, auditory hallucinations and delusions.

People with schizophrenia are likely to have additional conditions, including major depression and anxiety.

The strong familial link of schizophrenia is thought to be as high as 81 percent, and researchers have suggested that schizophrenia-related brain abnormalities may be present in unaffected relatives, a notion that has been supported by several studies.

For the current study, Heleen Boos and a team from University Medical Center Utrecht performed structural magnetic resonance imaging (MRI) whole-brain scans on 155 patients with schizophrenia, 186 of their non-psychotic siblings, and 122 healthy controls (including 25 sibling pairs).

Researchers used the images to measure volume, cortical thickness and to map the brain anatomy in order to evaluate group differences.

Compared with healthy controls, participants with schizophrenia had strong reductions in total brain, gray matter, and white matter volumes, and significant increases in lateral and third ventricle volumes after taking into account age, gender, intracranial volume, and left or right handedness.

However, there were no significant differences in brain volume between unaffected siblings and healthy controls.

Schizophrenia patients also showed cortical thinning compared with healthy controls, and had decreased gray matter density. Again, this was not found in unaffected siblings and healthy controls.

“Our study did not find structural brain abnormalities in nonpsychotic siblings of patients with schizophrenia compared with healthy control subjects, using multiple imaging methods,” the team says.

“This suggests that the structural brain abnormalities found in patients are most likely related to the illness itself.”

Source:  University Medical Center Utrecht 

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Increased Dopamine Can Reduce Impulsivity


Increased Dopamine Can Reduce ImpulsivityResearchers have discovered that elevating the level of the neurotransmitter dopamine in the frontal lobe of the brain can significantly decrease impulsivity in healthy adults.

The finding is important as impulsiveness is a risk factor for substance abuse.

“Impulsivity is a risk factor for addiction to many substances, and it has been suggested that people with lower dopamine levels in the frontal cortex tend to be more impulsive,” said lead author Andrew Kayser, Ph.D.

Researchers from the Ernest Gallo Clinic and Research Center at the University of California, San Francisco performed a double-blinded placebo study. The study has been published in the Journal of Neuroscience.

In the research, 23 adult research participants were given either tolcapone, a medication approved by the Food and Drug Administration (FDA) that inhibits a dopamine-degrading enzyme, or a placebo.

Investigators then gave the participants a task that measured impulsivity, asking them to make a hypothetical choice between receiving a smaller amount of money immediately (“smaller sooner”) or a larger amount at a later time (“larger later”).

Each participant was tested twice, once with tolcapone and once with placebo.

More impulse (at baseline) participants were more likely to choose the less impulsive “larger later” option after taking tolcapone than they were after taking the placebo.

Magnetic resonance imaging conducted while the participants were taking the test confirmed that regions of the frontal cortex associated with decision-making were more active in the presence of tolcapone than in the presence of placebo.

“To our knowledge, this is the first study to use tolcapone to look for an effect on impulsivity,” said Kayser.

The study is a proof-in-concept investigation and was not designed to investigate the reasons that reduced dopamine is linked with impulsivity.

However, explained Kayser, scientists believe that impulsivity is associated with an imbalance in dopamine between the frontal cortex, which governs executive functions such as cognitive control and self-regulation, and the striatum, which is thought to be involved in the planning and modification of more habitual behaviors.

“Most, if not all, drugs of abuse, such as cocaine and amphetamine, directly or indirectly involve the dopamine system,” said Kayser.

“They tend to increase dopamine in the striatum, which in turn may reward impulsive behavior. In a very simplistic fashion, the striatum is saying ‘go,’ and the frontal cortex is saying ‘stop.’ If you take cocaine, you’re increasing the ‘go’ signal, and the ‘stop’ signal is not adequate to counteract it.”

Kayser and his research team plan a follow-up study of the effects of tolcapone on drinking behavior.

“Once we determine whether drinkers can safely tolerate this medication, we will see if it has any effect on how much they drink while they’re taking it,” said Kayser.

Currently, Tolcapone is approved as a medication for Parkinson’s disease — a disease in which a chronic deficit of dopamine inhibits movement.

Source: University of California – San Francisco

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Memory Connections Change from Childhood to Adulthood


Memory Connections Change from Childhood to AdulthoodIn a new area of study, researchers explore how brain mechanisms for memory retrieval differ between adults and children.

Neuroscientists from Wayne State University and the Massachusetts Institute of Technology have discovered that while the memory systems are the same in many ways, the aging process appears to impart important differences in how we learn and respond to education.

Noa Ofen, Ph.D., an assistant professor in WSU’s Institute of Gerontology and Department of Pediatrics, says that cognitive ability, including the ability to learn and remember new information, dramatically changes between childhood and adulthood.

This ability parallels with dramatic changes that occur in the structure and function of the brain during these periods.

In the study, Ofen and her collaborative team tested the development of neural foundations of memory from childhood to young adulthood.

Researchers did this by exposing participants to pictures of scenes and then showing them the same scenes mixed with new ones. They then and asked them to judge whether each picture was presented earlier.

Participants made retrieval judgments while researchers collected images of their brains with magnetic resonance imaging (MRI).

Using this method, the researchers were able to see how the brain remembers. “Our results suggest that cortical regions related to attentional or strategic control show the greatest developmental changes for memory retrieval,” said Ofen.

This finding suggests that older participants use the cortical regions of the brain to retrieve past memories more so than younger participants.

“We were interested to see whether there are changes in the connectivity of regions in the brain that support memory retrieval,” Ofen added.

“We found changes in connectivity of memory-related regions. In particular, the developmental change in connectivity between regions was profound even without a developmental change in the recruitment of those regions, suggesting that functional brain connectivity is an important aspect of developmental changes in the brain.”

Researchers say this study is unique as it is the first time that the development of connectivity within memory systems in the brain has been tested.

Findings suggest the brain continues to rearrange connections to achieve adult-like performance during development.

Future studies by Ofen and her research team will focus on modeling brain network connectivity, and applying these methods to study abnormal brain development.

The team’s findings are published in the Journal of Neuroscience.

Source: Wayne State University

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Stress may delay brain development in early years


There has been a lot of work in animals linking both acute and chronic stress to changes in a part of the brain called the prefrontal cortex, which is involved in complex cognitive abilities like holding on to important information for quick recall and use,” says Jamie Hanson, a UW-Madison psychology graduate student. “We have now found similar associations in humans, and found that more exposure to stress is related to more issues with certain kinds of cognitive processes.”

Children who had experienced more intense and lasting stressful events in their lives posted lower scores on tests of what the researchers refer to as spatial working memory. They had more trouble navigating tests of short-term memory such as finding a token in a series of boxes, according to the study, which will be published in the June 6 issue of the Journal of Neuroscience.

Brain scans revealed that the anterior cingulate, a portion of the prefrontal cortex believed to play key roles in spatial working memory, takes up less space in children with greater exposure to very stressful situations.

“These are subtle differences, but differences related to important cognitive abilities” Hanson says.

But they maybe not irreversible differences.

“We’re not trying to argue that stress permanently scars your brain. We don’t know if and how it is that stress affects the brain,” Hanson says. “We only have a snapshot — one MRI scan of each subject — and at this point we don’t understand whether this is just a delay in development or a lasting difference. It could be that, because the brains is very plastic, very able to change, that children who have experienced a great deal of stress catch up in these areas.”

The researchers determined stress levels through interviews with children ages 9 to 14 and their parents. The research team, which included UW-Madison psychology professors Richard Davidson and Seth Pollak and their labs, collected expansive biographies of stressful events from slight to severe.

“Instead of focusing in on one specific type of stress, we tried to look at a range of stressors,” Hanson says. “We wanted to know as much as we could, and then use all this information to later to get an idea of how challenging and chronic and intense each experience was for the child.”

Interestingly, there was little correlation between cumulative life stress and age. That is, children who had several more years of life in which to experience stressful episodes were no more likely than their younger peers to have accumulated a length stress resume. Puberty, on the other hand, typically went hand-in-hand with heavier doses of stress.

The researchers, whose work was funded by the National Institutes of Health, also took note of changes in brain tissue known as white matter and gray matter. In the important brain areas that varied in volume with stress, the white and gray matter volumes were lower in tandem.

White matter, Hanson explained, is like the long-distance wiring of the brain. It connects separated parts of the brain so that they can share information. Gray matter “does the math,” Hanson says. “It takes care of the processing, using the information that gets shared along the white matter connections.”

Gray matter early in development appears to enable flexibility; children can play and excel at many different activities. But as kids age and specialize, gray matter thins. It begins to be “pruned” after puberty, while the amount of white matter grows into adulthood.

“For both gray and white matter, we actually see smaller volumes associated with high stress,” Hanson says. “Those kinds of effects across different kinds of tissue, those are the things we would like to study over longer periods of time. Understanding how these areas change can give you a better picture of whether this is just a delay in development or more lasting.”

More study could also show the researchers how to help children who have experienced an inordinate amount of stress.

“There are groups around the country doing working memory interventions to try to train or retrain people on this particular cognitive ability and improve performance,” Hanson says. “Understanding if and how stress affects these processes could help us know whether there may be similar interventions that could aid children living in stressful conditions, and how this may affect the brain.”

via Stress may delay brain development in early years.

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