Physical activity may leave the brain more open to change

Learning, memory, and brain repair depend on the ability of our neurons to change with experience. Now, researchers reporting in the Cell Press journal Current Biology on December 7 have evidence from a small study in people that exercise may enhance this essential plasticity of the adult brain. 

The findings focused on the visual cortex come as hopeful news for people with conditions including amblyopia (sometimes called lazy eye), traumatic brain injury, and more, the researchers say.

"We provide the first demonstration that moderate levels of physical activity enhance neuroplasticity in the visual cortex of adult humans," says Claudia Lunghi of the University of Pisa in Italy. 

"By showing that moderate levels of physical activity can boost the plastic potential of the adult visual cortex, our results pave the way to the development of non-invasive therapeutic strategies exploiting the intrinsic brain plasticity in adult subjects," she adds.

The plastic potential of the cerebral cortex is greatest early in life, when the developing brain is molded by experience. Brain plasticity is generally thought to decline with age. This decline in the brain's flexibility over time is especially pronounced in the sensory brain, which displays far less plasticity in adults than in younger people.

Lunghi and colleague Alessandro Sale of the National Research Council's Neuroscience Institute were inspired to explore the role of physical activity in brain plasticity by experiments that Sale conducted previously in laboratory animals. Those studies showed that animals performing physical activity--for example rats running on a wheel--showed elevated levels of plasticity in the visual cortex and improved recovery from amblyopia in comparison to more sedentary animals. 

To find out whether the same might hold true for people, the researchers measured the residual plastic potential of the adult visual cortex in humans using a simple test of binocular rivalry. Most of the time, our eyes work together. But when people have one eye patched for a short period of time, the closed eye becomes stronger as the visual brain attempts to compensate for the lack of visual input. The strength of the resulting imbalance between the eyes is a measure of the brain's visual plasticity and can be tested by presenting each eye with incompatible images. 

In the new study, Lunghi and Sale put 20 adults through this test twice; in one deprivation test, participants with one eye patched watched a movie while relaxing in a chair. In the other test, participants with one eye patched exercised on a stationary bike for ten-minute intervals during the movie. The results were clear: brain plasticity was enhanced by the exercise.

"We found that if, during the two hours of eye patching, the subject intermittently cycles, the perceptual effect of eye patching on binocular rivalry is stronger compared to a condition in which, during the two hours of patching, the subject watches a movie while sitting on a chair. That is, after physical activity, the eye that was patched is strongly potentiated, indicating increased levels of brain plasticity."

While further study is needed, the researchers think that this effect may result from a decrease with exercise in an inhibitory neurotransmitter called GABA. As concentrations of this inhibitory nerve messenger decline, the brain becomes more responsive. 

Regardless of the mechanism, the findings suggest that exercise plays an important role in brain health and recovery. They come as especially good news for people with amblyopia, which is generally considered to be untreatable in adults. 

"Our study suggests that physical activity, which is also beneficial for the general health of the patient, could be used to increase the efficiency of the treatment in adult patients," Lunghi says. "So, if you have a lazy eye, don't be lazy yourself!"

Lunghi and Sale say they now plan to investigate the effects of moderate levels of physical exercise on visual function in amblyopic adult patients and to look deeper into the underlying neural mechanisms.

Negative beliefs about aging predict Alzheimer's disease i

  

Newly published research led by the Yale School of Public Health demonstrates that individuals who hold negative beliefs about aging are more likely to have brain changes associated with Alzheimer's disease.

The study suggests that combatting negative beliefs about aging, such as elderly people are decrepit, could potentially offer a way to reduce the rapidly rising rate of Alzheimer's disease, a devastating neurodegenerative disorder that causes dementia in more than 5 million Americans.

The study led by Becca Levy, associate professor of public health and of psychology, is the first to link the brain changes related to Alzheimer's disease to a cultural-based psychosocial risk factor. The findings were published online Dec. 7 in the journal Psychology and Aging.

"We believe it is the stress generated by the negative beliefs about aging that individuals sometimes internalize from society that can result in pathological brain changes," said Levy. "Although the findings are concerning, it is encouraging to realize that these negative beliefs about aging can be mitigated and positive beliefs about aging can be reinforced, so that the adverse impact is not inevitable."

Study authors examined healthy, dementia-free subjects from the Baltimore Longitudinal Study of Aging, the nation's longest-running scientific study of aging. Based on MRIs, the researchers found that participants who held more negative beliefs about aging showed a greater decline in the volume of the hippocampus, a part of the brain crucial to memory. Reduced hippocampus volume is an indicator of Alzheimer's disease. 

Then researchers used brain autopsies to examine two other indicators of Alzheimer's disease: amyloid plaques, which are protein clusters that build up between brain cells; and neurofibrillary tangles, which are twisted strands of protein that build up within brain cells. Participants holding more negative beliefs about aging had a significantly greater number of plaques and tangles. The age stereotypes were measured an average of 28 years before the plaques and tangles.

In both stages of the study, Levy and her colleagues adjusted for other known risk factors for Alzheimer's disease, including health and age.

'Purpose in life' linked to lower mortality and cardiovascular risk

People who have a higher sense of purpose in life are at lower risk of death and cardiovascular disease, reports a pooled data analysis in Psychosomatic Medicine: Journal of Biobehavioral Medicine, the official journal of the American Psychosomatic Society. The journal is published by Wolters Kluwer."Possessing a high sense of purpose in life is associated with a reduced risk for mortality and cardiovascular events," according to the study by Drs. Randy Cohen and Alan Rozanski and colleagues at Mt. Sinai St. Luke's-Roosevelt Hospital, New York. While the mechanisms behind the association remain unclear, the findings suggest that approaches to strengthening a sense of purpose might lead to improved health outcomes.

How Does Purpose in Life Affect Health and Mortality Risks?
 
Using a technique called meta-analysis, the researchers pooled data from previous studies evaluating the relationship between purpose in life and the risk of death or cardiovascular disease. The analysis included data on more than 136,000 participants from ten studies--mainly from the United States or Japan. The US studies evaluated a sense of purpose or meaning in life, or "usefulness to others." The Japanese studies assessed the concept of ikigai, translated as "a life worth living."

The study participants, average age 67 years, were followed up for an average of seven years. During this time, more than 14,500 participants died from any cause while more than 4,000 suffered cardiovascular events (heart attack, stroke, etc).

The analysis showed a lower risk of death for participants with a high sense of purpose in life. After adjusting for other factors, mortality was about one-fifth lower for participants reporting a strong sense of purpose, or ikigai.

A high sense of purpose in life was also related to a lower risk of cardiovascular events. Both associations remained significant on analysis of various subgroups, including country, how purpose in life was measured, and whether the studies included participants with pre-existing cardiovascular disease.

There is a well-documented link between "negative psychosocial risk factors" and adverse health outcomes, including heart attack, stroke, and overall mortality. "Conversely, more recent study provides evidence that positive psychosocial factors can promote healthy physiological functioning and greater longevity," according to the authors.

The new analysis assembles high-quality data from studies assessing the relationship between purpose life and various measures of health and adverse clinical outcomes. The researchers write, "Together, these findings indicate a robust relationship between purpose in life and mortality and/or adverse cardiovascular outcomes."

While further studies are needed to determine how purpose in life might promote health and deter disease, preliminary data suggest a few basic mechanisms. The association might be explained physiologically, such as by buffering of bodily responses to stress; or behaviorally, such as by a healthier lifestyle.

"Of note, having a strong sense of life purpose has long been postulated to be an important dimension of life, providing people with a sense of vitality motivation and resilience," Dr. Rozanski comments. "Nevertheless, the medical implications of living with a high or low sense of life purpose have only recently caught the attention of investigators. The current findings are important because they may open up new potential interventions for helping people to promote their health and sense of well-being."

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Click here to read "Purpose in Life and Its Relationship to All-Cause Mortality and Cardiovascular Events: A Meta-Analysis."

Males who had participated in amateur contact sports in their youth have increased risk of degenerative disorder

Scientists have recently found evidence that professional football players are susceptible to a progressive degenerative disease, chronic traumatic encephalopathy (CTE), which is caused by repetitive brain trauma. Now, researchers on Mayo Clinic's Florida campus have discovered a significant and surprising amount of CTE in males who had participated in amateur contact sports in their youth.

About one-third of these men whose brains had been donated to the Mayo Clinic Brain Bank had evidence of CTE pathology. CTE only can be diagnosed posthumously.

The Mayo study, published in the December issue of Acta Neuropathologica, links amateur contact sports -- football, boxing, wrestling, rugby, basketball, baseball and others played while in school -- with the development of CTE, which when severe can affect mood, behavior and cognition.

"The 32 percent of CTE we found in our brain bank is surprisingly high for the frequency of neurodegenerative pathology within the general population," says the study's lead author, Kevin Bieniek, a predoctoral student in Mayo Graduate School's Neurobiology of Disease program.
"If 1 in 3 individuals who participate in a contact sport goes on to develop CTE pathology, this could present a real challenge down the road," Bieniek says. It remains to be determined if the brain changes produce any observable effects on behavior or cognition of the former athletes.

This study is the first to use CTE neuropathologic criteria established by the National Institute of Neurological Disorders and Stroke (NINDS) earlier this year to look for incidence of the disease in nonprofessional athletes, says the study's senior author, Dennis Dickson, M.D., a neuropathologist at Mayo Clinic.

"Using these criteria, Bieniek's report is the first detailed description of CTE pathology in a brain bank. As such, his work is groundbreaking," Dr. Dickson says. "The frequency with which he found CTE pathology in former athletes exposed to contact sports was surprising. It is pathology that had gone previously unrecognized." Bieniek is a member of Dr. Dickson's laboratory.

"The purpose of our study is not to discourage children and adults from participating in sports because we believe the mental and physical health benefits are great," Bieniek says. "It is vital that people use caution when it comes to protecting the head. Through CTE awareness, greater emphasis will be placed on making contact sports safer, with better protective equipment and fewer head-to-head contacts."

Bieniek led the team that examined the clinical records of 1,721 cases in the Mayo Clinic Brain Bank. They found 66 males who had documented participation in contact sports during their youth and young adult years. Of these cases, 32 percent had CTE pathology when the researchers examined brain tissue. In comparison, none of the 198 brains of individuals without documentation of participation in contact sports, including 66 women, had CTE pathology.

The researchers also compared a number of clinical and genetic features between cases with and without CTE pathology, and found two genetic markers that seemed to possibly modify risk of developing CTE. "These markers need to be further studied in a larger group of CTE cases, but they could be very important in determining whether an individual is at greater risk of developing these brain changes," Bieniek says.

Bieniek notes that the Mayo Clinic Brain Bank includes donors who have died with varying disorders of dementia. "We decided to examine our brain bank of neurodegenerative disorders, because CTE, found in older people, rarely occurs in isolation," Bieniek says. "Many cases of CTE previously reported have other neurodegenerative pathologies in addition to CTE. So, the same risk factors that may increase risk for other neurodegenerative diseases could very well play a role in development of CTE."

Slow walking speed in elderly signals Alzheimer's disease

How fast elderly people walk may be related to the amount of amyloid they have built up in their brains, even if they don't yet have symptoms of Alzheimer's disease, according to a study published in the December 2, 2015, online issue of Neurology®, the medical journal of the American Academy of Neurology.

The study involved 128 people with an average age of 76 who did not have dementia but were considered at high risk for developing it because they had some concerns about their memory. The participants had positron emission tomography (PET) scans of their brains to measure amyloid plaques in the brain. These plaques consist of dense deposits of a protein called beta amyloid, and their progressive buildup in the brain has been associated with the development of Alzheimer's disease. Of the participants, 48 percent had a level of amyloid often associated with dementia.

Participants were also tested on thinking and memory skills and how well they could complete everyday activities. A total of 46 percent of the participants had mild cognitive impairment, which can be a precursor to the dementia that occurs in Alzheimer's disease.

Walking speed was measured with a standard test that times people on how fast they can walk about 13 feet at their usual pace. The average walking speed was 3.48 feet per second. All but two of the participants tested in the normal range of walking speed.

The researchers found an association between slow walking speed and amyloid in several areas of the brain, including the putamen, a key region involved in motor function. The researchers compared how fast people walked both with and without taking into account the amount of amyloid and found that the amyloid level accounted for up to 9 percent of the difference in walking speed.

The relationship between amyloid levels and walking speed did not change when researchers took into account age, education level, or amount of memory problems.

"It's possible that having subtle walking disturbances in addition to memory concerns may signal Alzheimer's disease, even before people show any clinical symptoms," said study author Natalia del Campo, PhD, of the Gerontopole and the Centre of Excellence in Neurodegeneration of Toulouse (University Hospital Toulouse) in France.

Del Campo noted that the study looked only at a snapshot in time and does not prove that amyloid plaques cause the slowdown in walking speed; it shows the association. She also noted there are many other causes of slow walking in older adults.

How much TV you watch as a young adult may affect midlife cognitive function

Watching a lot of TV and having a low physical activity level as a young adult were associated with worse cognitive function 25 years later in midlife, according to an article published online by JAMA Psychiatry.
Few studies have investigated the association between physical activity in early adulthood and cognitive function later in life. Coupled with the increasing prevalence of sedentary or screen-based activities, such as watching television, these trends are of concern for upcoming generations of young people.

Tina D. Hoang, M.S.P.H., of the Northern California Institute for Research and Education at the Veterans Affairs Medical Center, San Francisco, Kristine Yaffe, M.D., of the University of California, San Francisco, and coauthors examined associations between 25-year patterns of television viewing and physical activity and midlife cognition.

The study of 3,247 adults (ages 18 to 30) used a questionnaire to assess television viewing and physical activity during repeated visits over 25 years. High television viewing was defined as watching TV for more than three hours per day for more than two-thirds of the visits and exercise was measured as units based on time and intensity. Cognitive function was evaluated at year 25 using three tests that assessed processing speed, executive function and verbal memory.

Participants with high television viewing during 25 years (353 of 3,247 or 10.9 percent) were more likely to have poor cognitive performance on some of the tests. Low physical activity during 25 years in 528 of 3,247 participants (16.3 percent) was associated with poor performance on one of the tests. The odds of poor cognitive performance were almost two times higher for adults with both high television viewing and low physical activity in 107 of 3,247 (3.3 percent) participants, according to the results.

The authors acknowledge a few limitations, including possible selection bias and that physical activity and TV viewing were self-reported.

"In this biracial cohort followed for 25 years, we found that low levels of physical activity and high levels of television viewing during young to mid-adulthood were associated with worse cognitive performance in midlife. In particular, these behaviors were associated with slower processing speed and worse executive function but not with verbal memory. Participants with the least active patterns of behavior (i.e., both low physical activity and high television viewing time) were the most likely to have poor cognitive function. ... Individuals with both low physical activity and high sedentary behavior may represent a critical target group," the study concludes.

Study highlights the importance of physical activity and aerobic exercise for healthy brain function

Regardless of gender, young adults who have greater aerobic fitness also have greater volume of their entorhinal cortex, an area of the brain responsible for memory. Better aerobic fitness however does not appear to impact hippocampal volume, another area in the brain responsible for memory.

While aerobic fitness is not directly associated with performance on a recognition memory task, the participants with a larger entorhinal cortex also performed better on the recognition memory task. These findings by Boston University School of medicine (BUSM) researchers appear in the journal NeuroImage.

The entorhinal cortex is a brain area known to show early pathology in Alzheimer's disease, which is characterized by profound memory impairment. Because of the strong association between hippocampal cell growth and exercise in models, previous work on exercise and the brain has not focused on the entorhinal cortex, despite its critical role in learning and memory until now.

The researchers recruited healthy young adults (ages 18-35 years) who underwent a treadmill test to measure aerobic capacity. During this test, the amount of oxygen and carbon dioxide in the participants' breath as they walked or ran on a treadmill was measured. Participants then underwent magnetic resonance imaging and performed a recognition memory task. Entorhinal and hippocampal volume was determined using a method known as voxel-based morphometry and then regression analysis to examine whether recognition memory and aerobic fitness predicted brain volumes.

"Our results suggest that aerobic exercise may have a positive effect on the medial temporal lobe memory system (which includes the entorhinal cortex) in healthy young adults. This suggests that exercise training, when designed to increase aerobic fitness, might have a positive effect on the brain in healthy young adults," explained corresponding author and principal investigator Karin Schon, PhD, BUSM assistant professor of anatomy and neurobiology. The researchers point out that unlike previous work done in older adults, in this young adult sample hippocampal volume does not show an association with aerobic fitness.

Researchers said this work could support previous studies that suggest aerobic exercise may forestall cognitive decline in older individuals at risk of dementia, and extends the idea that exercise may be beneficial for brain health to younger adults. "This is critical given that obesity, which has recently been linked with cognitive deficits in young and middle-aged adults, and physical inactivity are on the rise in young adults," Schon said.