Posts tagged white matter
Articles and news from the latest research reports.
(Image caption: The complex shape of individual oligodendrocytes (OLs) and myelin in adult mice injected with tamoxifen. Credit: Sarah Jolly)
Myelin vital for learning new practical skills
New evidence of myelin’s essential role in learning and retaining new practical skills, such as playing a musical instrument, has been uncovered by UCL research. Myelin is a fatty substance that insulates the brain’s wiring and is a major constituent of ‘white matter’. It is produced by the brain and spinal cord into early adulthood as it is needed for many developmental processes, and although earlier studies of human white matter hinted at its involvement in skill learning, this is the first time it has been confirmed experimentally.
The study in mice, published in Science today, shows that new myelin must be made each time a skill is learned later in life and the structure of the brain’s white matter changes during new practical activities by increasing the number of myelin-producing cells. Furthermore, the team say once a new skill has been learnt, it is retained even after myelin production stops. These discoveries could prove important in finding ways to stimulate and improve learning, and in understanding myelin’s involvement in other brain processes, such as in cognition.
For a child to learn to walk or an adult to master a new skill such as juggling, new brain circuit activity is needed and new connections are made across large distances and at high speeds between different parts of the brain and spinal cord. For this, electrical signals fire between neurons connected by “axons” – thread-like extensions of their outer surfaces which can be viewed as the ‘wire’ in the electric circuit. When new signals fire repeatedly along axons, the connections between the neurons strengthen, making them easier to fire in the same pattern in future. Neighbouring myelin-producing cells called oligodendrocytes (OLs) recognise the repeating signal and wrap myelin around the active circuit wiring. It is this activity-driven insulation that the team identified as essential for learning.
The team demonstrated that young adult mice need to make myelin to learn new motor skills but that new myelin does not need to be produced to recall and perform a pre-learned skill. They tested the ability of mice to learn to run on a complex wheel with irregularly spaced rungs. The study looked at thirty-six normal mice and thirty-two mice with a drug-controlled genetic switch to prevent new OLs and myelin from being made. They found the mice that were prevented from producing new myelin could not master the complex wheel, whereas those that could produce myelin did learn, with differences between the two groups’ abilities seen after only two hours of practice.
A second experiment looked at mice that were first allowed to learn to run on the complex wheel before being treated with the drug to prevent further myelin production. When the mice were later re-introduced to the complex wheel, they were immediately able to run at top speed without having to spend time re-learning. This shows that the inability to make new myelin did not affect the mouse’s running ability and that new myelin is not required to remember and perform a skill once learned; it is required only during the initial learning phase.
Lead researcher, Professor Bill Richardson, Director of the UCL Wolfson Institute for Biomedical Research, said: “From earlier studies of human white matter using advanced MRI technology, we thought OLs and myelin might be involved in some way in skill learning, so we decided to attack this idea experimentally. We were surprised how quickly we saw differences in the ability of mice from each group to learn how to run on complex wheel, which shows just how fast the brain can respond to wrap newly-activated circuits in myelin and how this improves learning. This rapid response suggests that a number of alternative axon pathways might already exist in the brain that could be used to drive a particular sequence of movements, but it quickly works out which of those circuits is most efficient and both selects and protects its chosen route with myelin.
“We think these findings are really exciting as they open up opportunities to investigate the role of OLs and myelin in other brain processes, such as cognitive activities (like navigating through a maze), to see if the requirement for new myelin is general or specific to motor activity. I’m keen to find out the precise sequence of changes to OLs and myelin during learning and whether these changes are needed more in some parts of the brain than others, which might shed light on some of the mysteries still surrounding how the brain adapts and learns throughout life.”
Cooling of Dialysis Fluids Protects Against Brain Damage
While dialysis can cause blood pressure changes that damage the brain, cooling dialysis fluids can protect against such effects. The findings come from a study appearing in an upcoming issue of the Journal of the American Society of Nephrology (JASN). The cooling intervention can be delivered without additional cost and is simple to perform.
While dialysis is an essential treatment for many patients with kidney disease, it can cause damage to multiple organs, including the brain and heart, due to the sudden removal of bodily fluids.
To characterize dialysis-induced brain injury and to see whether cooled dialysis fluids (called dialysate) might help reduce such injury, Christopher McIntyre, DM, and his colleagues randomized 73 new dialysis patients to dialyze with body temperature dialysate or dialysate cooled to 0.5◦C below body temperature for 1 year.
The study demonstrated that dialysis drives progressive white matter brain injury due to blood pressure instability; however, patients who dialyzed at 0.5◦C below body temperature were completely protected against such white matter changes.
“This study demonstrates that paying attention to improving the tolerability of dialysis treatment—in this case by the simple and safe intervention of reducing the temperature of dialysate—does not just make patients feel better, but also can completely protect the brain from progressive damage,” said Dr. McIntyre.
(Source: newswise.com)
Scientists track the rise and fall of brain volume throughout life
We can witness our bodies mature, then gradually grow wrinkled and weaker with age, but it is only recently that scientists have been able to track a similar progression in the nerve bundles of our brains. That tissue increases in volume until around age 40, then slowly shrinks. By the end of our lives the tissue is about the volume of a 7-year-old.
So finds a team of Stanford scientists who used a new magnetic resonance imaging technique to show, for the first time, how human brain tissue changes throughout life. Knowing what’s normal at different ages, doctors can now image a patient’s brain, compare it to this standard curve and be able to tell if a person is out of the normal range, much like the way a growth chart can help identify kids who have fallen below their growth curve. The researchers have already used the technique to identify previously overlooked changes in the brain of people with multiple sclerosis.
"This allows us to look at people who have come into the clinic, compare them to the norm and potentially diagnose or monitor abnormalities due to different diseases or changes due to medications," said Jason Yeatman, a graduate student in psychology and first author on a paper published today in Nature Communications. Aviv Mezer, a research associate, was senior author on the paper. Both collaborated with Brian Wandell, a professor of psychology, and his team.
For decades scientists have been able to image the brain using magnetic resonance imaging (MRI) and detect tumors, brain activity or abnormalities in people with some diseases, but those measurements were all subjective. A scientist measuring some aspect of the brain in one lab couldn’t directly compare findings with someone in another lab. And because no two scans could be compared, there was no way to look at a patient’s image and know whether it fell outside the normal range.
Limitation overcome
"A big problem in MRI is variation between instruments," Mezer said. Last year Mezer and Wandell led an interdisciplinary team to develop a technique that can be used to compare MRI scans quantitatively between labs, described in Nature Medicine. “Now with that method we found a way to measure the underlying tissue and not the instrumental bias. So that means that we can measure 100 subjects here and Jason can measure another 100 in Seattle (where he is now a postdoctoral fellow) and we can put them all in a database for the community.”
The technique the team had developed measures the amount of white matter tissue in the brain. That amount of white matter comes primarily from an insulating covering called myelin that allows nerves to fire most efficiently and is a hallmark of brain maturation, though the white matter can also be composed of other types of cells in the brain.
White matter plays a critical role in brain development and decline, and several diseases including schizophrenia and autism are associated with white matter abnormalities. Despite its importance in normal development and disease, no metric existed for determining whether any person’s white matter fell within a normal range, particularly if the people were imaged on different machines.
Mezer and Yeatman decided to use the newly developed quantitative technique to develop a normal curve for white matter levels throughout life. They imaged 24 regions within the brains of 102 people ages 7 to 85, and from that established a set of curves showing the increase and then eventual decrease in white matter in each of the 24 regions throughout life.
What they found is that the normal curve for brain composition is rainbow-shaped. It starts and ends with roughly the same amount of white matter and peaks between ages 30 and 50. But each of the 24 regions changes a different amount. Some parts of the brain, like those that control movement, are long, flat arcs, staying relatively stable throughout life.
Others, like the areas involved in thinking and learning, are steep arches, maturing dramatically and then falling off quickly. (The group did point out that their samples started at age 7 and a lot of brain development had already occurred.)
Continued collaboration
"Regions of the brain supporting high-level cognitive functions develop longer and have more degradation," Yeatman said. "Understanding how that relates to cognition will be really important and interesting." Yeatman is now a postdoctoral scholar at the University of Washington, and Mezer is now an assistant professor at the Hebrew University of Jerusalem. They plan to continue collaborating with each other and with other members of the Wandell lab, looking at how brain composition correlates with learning and how it could be used to diagnose diseases, learning disabilities or mental health issues.
The group has already shown that they can identify people with multiple sclerosis (MS) as falling outside the normal curve. People with MS develop what are known as lesions – regions in the brain or spinal cord where myelin is missing. In this paper, the team showed that they could identify people with MS as being off the normal curve throughout regions of the brain, including places where there are no visible lesions. This could provide an alternate method of monitoring and diagnosing MS, they say.
Wandell has had a particular interest in studying the changes that happen in the brain as a child learns to read. Until now, if a family brought a child into the clinic with learning disabilities, Wandell and other scientists had no way to diagnose whether the child’s brain was developing normally, or to determine the relationship between learning delays and white matter abnormalities.
"Now that we know what the normal distribution is, when a single person comes in you can ask how their child compares to the normal distribution. That’s where this is headed," said Wandell, who is also the Isaac and Madeline Stein Family professor and a Stanford Bio-X affiliate. Wandell runs the Center for Cognitive and Neurobiological Imaging (CNI), where Mezer and the team developed the MRI technique to quantify white matter, and where the scans for this study were conducted.
The ability to share data among scientists is an issue Wandell has championed at the CNI and has been promoting in his work helping the Stanford Neurosciences Institute plan the computing strategy for their new facility. “Sharing of data and computational methods is critical for scientific progress,” Wandell said. In line with that goal, the new standard curve for white matter is something scientists around the world can use and contribute data to.
Study links physical activity in older adults to brain white-matter integrity
Like everything else in the body, the white-matter fibers that allow communication between brain regions also decline with age. In a new study, researchers found a strong association between the structural integrity of these white-matter tracts and an older person’s level of daily activity – not just the degree to which he or she engaged in moderate or vigorous exercise, but also whether the person was sedentary the rest of the time.
The study, reported in the journal PLOS ONE, tracked physical activity in 88 healthy but “low-fit” participants aged 60 to 78. The participants agreed to wear accelerometers during most of their waking hours over the course of a week, and also submitted to brain imaging.
“To our knowledge, this is the first study of its kind that uses an objective measure of physical activity along with multiple measures of brain structure,” said University of Illinois postdoctoral researcher Agnieszka Burzynska, who conducted the research with U. of I. Beckman Institute director Arthur Kramer and kinesiology and community health professor Edward McAuley.
Most studies ask subjects to describe how much physical activity they get, which is subjective and imprecise, Burzynska said. The accelerometer continuously tracks a person’s movement, “so it’s not what they say they do or what they think they do, but we have measured what they are actually doing,” she said.
The researchers assumed that participants’ activity levels over a week accurately reflected their overall engagement, or lack of engagement, in physical activity.
The study also relied on two types of brain imaging. The first, diffusion tensor imaging, offers insight into the structural integrity of a tissue by revealing how water is diffused in the tissue. The second method looks for age-related changes in white matter, called lesions. Roughly 95 percent of adults aged 65 and older have such lesions, Burzynska said. While they are a normal part of aging, their early onset or rapid accumulation may spell trouble, she said.
The team found that the brains of older adults who regularly engaged in moderate-to-vigorous exercise generally “showed less of the white-matter lesions,” Burzynska said.
The association between physical activity and white-matter structural integrity was region-specific, the researchers reported. Older adults who engaged more often in light physical activity had greater structural integrity in the white-matter tracts of the temporal lobes, which lie behind the ears and play a key role in memory, language, and the processing of visual and auditory information.
In contrast, those who spent more time sitting had lower structural integrity in the white-matter tracts connecting the hippocampus, “a structure crucial for learning and memory,” Burzynska said.
“This relationship between the integrity of tracts connecting the hippocampus and sedentariness is significant even when we control for age, gender and aerobic fitness,” she said. “It suggests that the physiological effect of sitting too much, even if you still exercise at the end of the day for half an hour, will have a detrimental effect on your brain.”
The findings suggest that engaging in physical activity and avoiding a sedentary lifestyle are both important for brain health in older age, Burzynska said.
“We hope that this will encourage people to take better care of their brains by being more active,” she said.
Study First to Use Brain Scans to Forecast Early Reading Difficulties
UC San Francisco researchers have used brain scans to predict how young children learn to read, giving clinicians a possible tool to spot children with dyslexia and other reading difficulties before they experience reading challenges.
In the United States, children usually learn to read for the first time in kindergarten and become proficient readers by third grade, according to the authors. In the study, researchers examined brain scans of 38 kindergarteners as they were learning to read formally at school and tracked their white matter development until third grade. The brain’s white matter is essential for perceiving, thinking and learning.
The researchers found that the developmental course of the children’s white matter volume predicted the kindergarteners’ abilities to read.
“We show that white matter development during a critical period in a child’s life, when they start school and learn to read for the very first time, predicts how well the child ends up reading,” said Fumiko Hoeft, MD, PhD, senior author and an associate professor of child and adolescent psychiatry at UCSF, and member of the UCSF Dyslexia Center.
The research is published online in Psychological Science.
Doctors commonly use behavioral measures of reading readiness for assessments of ability. Other measures such as cognitive (i.e. IQ) ability, early linguistic skills, measures of the environment such as socio-economic status, and whether there is a family member with reading problems or dyslexia are all common early factors used to assess risk of developing reading difficulties.
“What was intriguing in this study was that brain development in regions important to reading predicted above and beyond all of these measures,” said Hoeft.
The researchers removed the effects of these commonly used assessments when doing the statistical analyses in order to assess how the white matter directly predicted future reading ability. They found that left hemisphere white matter in the temporo-parietal region just behind and above the left ear — thought to be important for language, reading and speech — was highly predictive of reading acquisition beyond effects of genetic predisposition, cognitive abilities, and environment at the outset of kindergarten. Brain scans improved prediction accuracy by 60 percent better at predicting reading difficulties than the compared to traditional assessments alone.
“Early identification and interventions are extremely important in children with dyslexia as well as most neurodevelopmental disorders,” said Hoeft. “Accumulation of research evidence such as ours may one day help us identify kids who might be at risk for dyslexia, rather than waiting for children to become poor readers and experience failure.”
According to the National Institute of Child and Human Development, as many as 15 percent of Americans have major trouble reading.
“Examining developmental changes in the brain over a critical period of reading appears to be a unique sensitive measure of variation and may add insight to our understanding of reading development in ways that brain data from one time point, and behavioral and environmental measures, cannot,” said Chelsea Myers, BS, lead author and lab manager in UCSF’s Laboratory for Educational NeuroScience. “The hope is that understanding each child’s neurocognitive profiles will help educators provide targeted and personalized education and intervention, particularly in those with special needs.”
(Source: ucsf.edu)
Brain damage caused by severe sleep apnea is reversible
A neuroimaging study is the first to show that white matter damage caused by severe obstructive sleep apnea can be reversed by continuous positive airway pressure therapy. The results underscore the importance of the “Stop the Snore” campaign of the National Healthy Sleep Awareness Project, a collaboration between the Centers for Disease Control and Prevention, American Academy of Sleep Medicine, Sleep Research Society and other partners.
Results show that participants with severe, untreated sleep apnea had a significant reduction in white matter fiber integrity in multiple brain areas. This brain damage was accompanied by impairments to cognition, mood and daytime alertness. Although three months of CPAP therapy produced only limited improvements to damaged brain structures, 12 months of CPAP therapy led to an almost complete reversal of white matter abnormalities. Treatment also produced significant improvements in nearly all cognitive tests, mood, alertness and quality of life.
“Structural neural injury of the brain of obstructive sleep apnea patients is reversible with effective treatment,” said principal investigator and lead author Vincenza Castronovo, PhD, clinical psychologist at the Sleep Disorders Center at San Raffaele Hospital and Vita-Salute San Raffaele University in Milano, Italy. “Treatment with CPAP, if patients are adherent to therapy, is effective for normalizing the brain structure.”
The study results are published in the September issue of the journal Sleep.
“Obstructive sleep apnea is a destructive disease that can ruin your health and increase your risk of death,” said American Academy of Sleep Medicine President Dr. Timothy Morgenthaler, a national spokesperson for the Healthy Sleep Project. “Treatment of sleep apnea can be life-changing and potentially life-saving.”
The “Stop the Snore” campaign was launched recently to encourage people to talk to a doctor about the warning signs for sleep apnea, which afflicts at least 25 million adults in the U.S. Sleep apnea warning signs include snoring and choking, gasping or silent breathing pauses during sleep. Pledge to stop the snore at www.stopsnoringpledge.org.
The study involved 17 men with severe, untreated obstructive sleep apnea who had an average age of 43 years. They were evaluated at baseline and after both three months and 12 months of treatment with CPAP therapy. At each time point they underwent a neuropsychological evaluation and a diffusion tensor imaging examination. DTI is a form of magnetic resonance imaging that measures the flow of water through brain tissue. Participants were compared with 15 age-matched, healthy controls who were evaluated only at baseline.
A previous study by Castronovo’s research team found similar damage to gray matter volume in multiple brain regions of people with severe sleep apnea. Improvements in gray matter volume appeared after three months of CPAP therapy. According to the authors, the two studies suggest that the white matter of the brain takes longer to respond to treatment than the gray matter.
“We are seeing a consistent message that the brain can improve with treatment,” said co-principal investigator Mark Aloia, PhD, Associate Professor of Medicine at National Jewish Health in Denver, Colorado, and Senior Director of Global Clinical Research for Philips Respironics, Inc. “We know that PAP therapy keeps people breathing at night; but demonstrating effects on secondary outcomes is critical, and brain function and structure are strong secondary outcomes.”
Longitudinal study explores white matter damage, cognition after traumatic axonal injury
Traumatic Axonal Injury is a form of traumatic brain injury that can have detrimental effects on the integrity of the brain’s white matter and lead to cognitive impairments. A new study from the Center for BrainHealth at The University of Texas at Dallas investigated white matter damage in the acute and chronic stages of a traumatic axonal injury in an effort to better understand what long-term damage may result.
The study, published online July 21 in the Journal of Neurotrauma, looked at 13 patients ages 16 to 60 with mild to severe brain injuries from the intensive care unit at a Level I trauma center. This group was matched to a cohort of 10 healthy individuals resembling the age, gender, and ethnicity of the patients. White matter integrity was measured using diffusion tensor imaging (DTI) in the acute stage of injury, at day one, and again at the chronic stage, seven months post-injury. In addition, neuropsychological assessments measured cognitive performance including processing speed, attention, learning and memory at both stages after injury.
“We intended to determine whether DTI could not only identify early compromise to white matter, but also demonstrate an association with functional and neuropsychological outcomes months post-injury,” said Carlos Marquez de la Plata, Ph.D., Assistant Director of Rehabilitation Research at Pate Rehabilitation in Dallas, Texas.
The study’s findings suggest DTI may be used to detect meaningful changes in white matter as early as one day after a traumatic brain injury. White matter integrity measured at the chronic stage was also found to significantly correlate with cognitive processing speed.
“On the first day after the injury, we found white matter integrity was compromised due to swelling in the brain,“ said the study’s lead author Alison Perez. “As the swelling subsided over time and the brain began to repair itself, we found that many of the damaged neurons that were unable to repair themselves began to die off, which appears to slow the speed of cognitive processing.”
Interestingly, the degree of white matter compromise detected early after injury was associated with markers of injury severity such as the number of days in the intensive care unit and hospital, but not to outcomes months later.
At seven months post-injury, many of the patients’ cognitive performance improved including processing speed, divided attention, and short and long-term memory. In addition, patients with better white matter integrity at the chronic stage had the fastest processing speed.
By studying the long-term effects of a traumatic axonal injury at both the acute and chronic stages, researchers hope to assist in the advancement of future assessment and treatment options after a traumatic brain injury.
Wii Balance Board Induces Changes in the Brains of MS Patients
A balance board accessory for a popular video game console can help people with multiple sclerosis (MS) reduce their risk of accidental falls, according to new research published online in the journal Radiology. Magnetic resonance imaging (MRI) scans showed that use of the Nintendo Wii Balance Board system appears to induce favorable changes in brain connections associated with balance and movement.
Balance impairment is one of the most common and disabling symptoms of MS, a disease of the central nervous system in which the body’s immune system attacks the protective sheath around nerve fibers. Physical rehabilitation is often used to preserve balance, and one of the more promising new tools is the Wii Balance Board System, a battery-powered device about the size and shape of a bathroom scale. Users stand on the board and shift their weight as they follow the action on the television screen during games like slalom skiing.
While Wii balance board rehabilitation has been reported as effective in patients with MS, little is known about the underlying physiological basis for any improvements in balance.
Researchers recently used an MRI technique called diffusion tensor imaging (DTI) to study changes in the brains of 27 MS patients who underwent a 12-week intervention using Wii balance board-based visual feedback training. DTI is a non-conventional MRI technique that allows detailed analysis of the white matter tracts that transmit nervous signals through the brain and body.
MRI scans of the MS patients showed significant effects in nerve tracts that are important in balance and movement. The changes seen on MRI correlated with improvements in balance as measured by an assessment technique called posturography.
These brain changes in MS patients are likely a manifestation of neural plasticity, or the ability of the brain to adapt and form new connections throughout life, according to lead author Luca Prosperini, M.D., Ph.D., from Sapienza University in Rome, Italy.
"The most important finding in this study is that a task-oriented and repetitive training aimed at managing a specific symptom is highly effective and induces brain plasticity," he said. "More specifically, the improvements promoted by the Wii balance board can reduce the risk of accidental falls in patients with MS, thereby reducing the risk of fall-related comorbidities like trauma and fractures."
Dr. Prosperini noted that similar plasticity has been described in persons who play video games, but the exact mechanisms behind the phenomenon are still unknown. He hypothesized that changes can occur at the cellular level within the brain and may be related to myelination, the process of building the protective sheath around the nerves.
The rehabilitation-induced improvements did not persist after the patients discontinued the training protocol, Dr. Prosperini said, most likely because certain skills related to structural changes to the brain after an injury need to be maintained through training.
"This finding should have an important impact on the rehabilitation process of patients, suggesting that they need ongoing exercises to maintain good performance in daily living activities," Dr. Prosperini said.
Abnormal White Matter Integrity in Chronic Users of Codeine-Containing Cough Syrups: A Tract-Based Spatial Statistics Study
BACKGROUND AND PURPOSE: Codeine-containing cough syrups have become one of the most popular drugs of abuse in young people in the world. Chronic codeine-containing cough syrup abuse is related to impairments in a broad range of cognitive functions. However, the potential brain white matter impairment caused by chronic codeine-containing cough syrup abuse has not been reported previously. Our aim was to investigate abnormalities in the microstructure of brain white matter in chronic users of codeine-containing syrups and to determine whether these WM abnormalities are related to the duration of the use these syrups and clinical impulsivity.
MATERIALS AND METHODS: Thirty chronic codeine-containing syrup users and 30 matched controls were evaluated. Diffusion tensor imaging was performed by using a single-shot spin-echo-planar sequence. Whole-brain voxelwise analysis of fractional anisotropy was performed by using tract-based spatial statistics to localize abnormal WM regions. The Barratt Impulsiveness Scale 11 was surveyed to assess participants’ impulsivity. Volume-of-interest analysis was used to detect changes of diffusivity indices in regions with fractional anisotropy abnormalities. Abnormal fractional anisotropy was extracted and correlated with clinical impulsivity and the duration of codeine-containing syrup use.
RESULTS: Chronic codeine-containing syrup users had significantly lower fractional anisotropy in the inferior fronto-occipital fasciculus of the bilateral temporo-occipital regions, right frontal region, and the right corona radiata WM than controls. There were significant negative correlations among fractional anisotropy values of the right frontal region of the inferior fronto-occipital fasciculus and the right superior corona radiata WM and Barratt Impulsiveness Scale total scores, and between the right frontal region of the inferior fronto-occipital fasciculus and nonplan impulsivity scores in chronic codeine-containing syrup users. There was also a significant negative correlation between fractional anisotropy values of the right frontal region of the inferior fronto-occipital fasciculus and the duration of codeine-containing syrup use in chronic users.
CONCLUSIONS: Chronic codeine-containing syrup abuse may be associated with disruptions in brain WM integrity. These WM microstructural deficits may be linked to higher impulsivity in chronic codeine-containing syrup users.
Physically fit kids have beefier brain white matter than their less-fit peers
A new study of 9- and 10-year-olds finds that those who are more aerobically fit have more fibrous and compact white-matter tracts in the brain than their peers who are less fit. “White matter” describes the bundles of axons that carry nerve signals from one brain region to another. More compact white matter is associated with faster and more efficient nerve activity.
The team reports its findings in the open-access journal Frontiers in Human Neuroscience.
“Previous studies suggest that children with higher levels of aerobic fitness show greater brain volumes in gray-matter brain regions important for memory and learning,” said University of Illinois postdoctoral researcher Laura Chaddock-Heyman, who conducted the study with kinesiology and community health professor Charles Hillman and psychology professor and Beckman Institute director Arthur Kramer. “Now for the first time we explored how aerobic fitness relates to white matter in children’s brains.”
The team used diffusion tensor imaging (DTI, also called diffusion MRI) to look at five white-matter tracts in the brains of the 24 participants. This method analyzes water diffusion into tissues. For white matter, less water diffusion means the tissue is more fibrous and compact, both desirable traits.
The researchers controlled for several variables – such as social and economic status, the timing of puberty, IQ, or a diagnosis of ADHD or other learning disabilities – that might have contributed to the reported fitness differences in the brain.
The analysis revealed significant fitness-related differences in the integrity of several white-matter tracts in the brain: the corpus callosum, which connects the brain’s left and right hemispheres; the superior longitudinal fasciculus, a pair of structures that connect the frontal and parietal lobes; and the superior corona radiata, which connect the cerebral cortex to the brain stem.
“All of these tracts have been found to play a role in attention and memory,” Chaddock-Heyman said.
The team did not test for cognitive differences in the children in this study, but previous work has demonstrated a link between improved aerobic fitness and gains in cognitive function on specific tasks and in academic settings.
“Previous studies in our lab have reported a relationship between fitness and white-matter integrity in older adults,” Kramer said. “Therefore, it appears that fitness may have beneficial effects on white matter throughout the lifespan.”
To take the findings further, the team is now two years into a five-year randomized, controlled trial to determine whether white-matter tract integrity improves in children who begin a new physical fitness routine and maintain it over time. The researchers are looking for changes in aerobic fitness, brain structure and function, and genetic regulation.
“Prior work from our laboratories has demonstrated both short- and long-term differences in the relation of aerobic fitness to brain health and cognition,” Hillman said. “However, our current randomized, controlled trial should provide the most comprehensive assessment of this relationship to date.”
The new findings add to the evidence that aerobic exercise changes the brain in ways that improve cognitive function, Chaddock-Heyman said.
“This study extends our previous work and suggests that white-matter structure may be one additional mechanism by which higher-fit children outperform their lower-fit peers on cognitive tasks and in the classroom,” she said.