Raw fruit and vegetables provide better mental health outcomes
April 16, 2018
Science Daily/University of Otago
Researchers have discovered raw fruit and vegetables may be better for your mental health than cooked, canned and processed fruit and vegetables.
Seeking the feel good factor? Go natural.
That is the simple message from University of Otago researchers who have discovered raw fruit and vegetables may be better for your mental health than cooked, canned and processed fruit and vegetables.
Dr Tamlin Conner, Psychology Senior Lecturer and lead author, says public health campaigns have historically focused on aspects of quantity for the consumption of fruit and vegetables (such as 5+ a day).
However, the study, just published in Frontiers in Psychology, found that for mental health in particular, it may also be important to consider the way in which produce was prepared and consumed.
"Our research has highlighted that the consumption of fruit and vegetables in their 'unmodified' state is more strongly associated with better mental health compared to cooked/canned/processed fruit and vegetables," she says.
Dr Conner believes this could be because the cooking and processing of fruit and vegetables has the potential to diminish nutrient levels.
"This likely limits the delivery of nutrients that are essential for optimal emotional functioning."
For the study, more than 400 young adults from New Zealand and the United States aged 18 to 25 were surveyed. This age group was chosen as young adults typically have the lowest fruit and vegetable consumption of all age groups and are at high risk for mental health disorders.
The group's typical consumption of raw versus cooked and processed fruits and vegetables were assessed, alongside their negative and positive mental health, and lifestyle and demographic variables that could affect the association between fruit and vegetable intake and mental health (such as exercise, sleep, unhealthy diet, chronic health conditions, socioeconomic status, ethnicity, and gender).
"Controlling for the covariates, raw fruit and vegetable consumption predicted lower levels of mental illness symptomology, such as depression, and improved levels of psychological wellbeing including positive mood, life satisfaction and flourishing. These mental health benefits were significantly reduced for cooked, canned, and processed fruits and vegetables.
"This research is increasingly vital as lifestyle approaches such as dietary change may provide an accessible, safe, and adjuvant approach to improving mental health," Dr Conner says.
* The top 10 raw foods related to better mental health were: carrots, bananas, apples, dark leafy greens such as spinach, grapefruit, lettuce, citrus fruits, fresh berries, cucumber, and kiwifruit.
https://www.sciencedaily.com/releases/2018/04/180416101403.htm
Obesity could be linked to early childhood behavior
February 27, 2018
Science Daily/University of Waterloo
New research has found that it is generally a combination of unhealthy behaviors among youth that could be the greatest predictors of whether or not young people will experience obesity issues in adulthood.
A study led by the University of Waterloo found it's generally a combination of unhealthy behaviours among youth that could be the greatest predictors of whether or not young people will experience obesity issues in adulthood.
The study concluded that public health efforts focusing on obesity prevention must identify and correct poor behaviours that are often developed in early childhood.
"Adolescents with obesity often maintain their weight status into adulthood, increasing their risk of developing cardiovascular disease, diabetes, and high blood pressure," says Rachel Laxer, who formed part of the research team while doing her PhD at Waterloo. "Public health practitioners should be targeting clusters of risky behaviours using a comprehensive and multi-pronged approach."
"Research tells us that while calorie intake has not dramatically changed over time, habits such as exercising, smoking, drug use and alcohol consumption have," said Laxer. "It's increasingly important to target these risky behaviours together, and early, before they become habits."
The study involved Ontario students in grades nine and ten, ranging from 13 to 17 years of age and participating in the COMPASS Study, a nine-year study started in 2012 that is funded by the Canadian Institute for Health Research.
Students reported risky behaviours at the beginning of the study, and their heights and weights were tracked for two additional years. Based on their reported behaviours, the teens were classified as Typical High School Athletes, Inactive High Screen-Users ("Screenagers"), Moderately Active Substance Users, or Health Conscious. The researchers found that although the four groups saw similar increases to their weight status over the years that they were followed, students in the Health Conscious group had the healthiest body weight at the beginning of the study.
"It's important to try to improve behaviours before they become habits, which are much harder to correct," said Laxer. "This could have important implications for public health initiatives. Intervening and modifying unhealthy behaviours earlier might have a greater impact than during adolescence. Health promotion strategies targeting higher risk youth as they enter secondary school might be the best way to prevent or delay the onset of obesity, and might have better public health outcomes over the longer term."
https://www.sciencedaily.com/releases/2018/02/180227111651.htm
Obesity increases dementia risk
November 30, 2017
Science Daily/University College London
People who have a high body mass index (BMI) are more likely to develop dementia than those with a normal weight, according to a new study.
The study, published in the Alzheimer's & Dementia journal, analysed data from 1.3 million adults living in the United States and Europe. The researchers also found that people near dementia onset, who then go on to develop dementia, tend to have lower body weight than their dementia-free counterparts.
"The BMI-dementia association observed in longitudinal population studies, such as ours, is actually attributable to two processes," said lead author of the study, Professor Mika Kivimäki (UCL Institute of Epidemiology & Health). "One is an adverse effect of excess body fat on dementia risk. The other is weight loss due to pre-clinical dementia. For this reason, people who develop dementia may have a higher-than-average body mass index some 20 years before dementia onset, but close to overt dementia have a lower BMI than those who remain healthy."
"The new study confirms both the adverse effect of obesity as well as weight loss caused by metabolic changes during the pre-dementia stage."
Past research on how a person's weight influences their risk of dementia has produced conflicting results. Some findings have suggested that being obese poses a higher dementia risk, but other studies have linked lower weight to increased dementia incidence.
In this study, researchers from across Europe pooled individual-level data from 39 longitudinal population studies from the United States, the United Kingdom, France, Sweden, and Finland. A total of 1,349,857 dementia-free adults participated in these studies and their weight and height were assessed. Dementia was ascertained using linkage to electronic health records obtained from hospitalisation, prescribed medication and death registries.
A total of 6,894 participants developed dementia during up to 38 years of follow-up. Two decades before symptomatic dementia, higher BMI predicted dementia occurrence: each 5-unit increase in BMI was associated with a 16-33% higher risk of this condition (5 BMI units is 14.5kg for a person 5'7" (170cm) tall, approximately the difference in weight between the overweight and normal weight categories or between the obese and overweight categories). In contrast, the mean level of BMI during pre-clinical stage close to dementia onset was lower compared to that in participants who remained healthy.
In 2015, the number of people with dementia reached almost 45 million, two times more than in 1990. This study suggests that maintaining a healthy weight could prevent, or at least delay, dementia.
https://www.sciencedaily.com/releases/2017/11/171130133812.htm
Brain's appetite regulator disrupted in obese teens
November 30, 2017
Science Daily/Radiological Society of North America
Researchers using advanced MRI to study obese adolescents found disrupted connectivity in the complex regions of the brain involved in regulating appetite, according to a new study.
According to the Centers for Disease Control and Prevention (CDC), obesity has more than quadrupled in adolescents over the past 30 years. It is estimated that more than one-third of children and adolescents in the U.S. are overweight or obese. Obesity in adolescence is associated with a number of health risks, including cardiovascular disease and diabetes.
The study at the University of Sao Paulo in Brazil included 59 obese adolescents between the ages of 11 and 18 and 61 healthy control adolescents matched for gender, age, socio-economical classification and education level. The adolescents were classified by the World Health Organization criterion for obesity. They had no other known chronic diseases or conditions. The study participants underwent diffusion tensor imaging (DTI) of the brain to evaluate white matter integrity.
DTI is a type of MRI exam that measures functional anisotropy (FA), the microscopic motion, or anisotropy, of water molecules within and surrounding the brain's white matter fibers. Low FA values indicate greater disruption within the white matter.
"DTI is a relatively new MRI technique not widely used in clinical diagnosis," said study author Pamela Bertolazzi, a biomedical scientist and Ph.D. student in the neuroimaging laboratory at the University of Sao Paulo.
The results showed loss of white matter integrity in several brain regions in the obese patients. Compared to the healthy controls, the brains of the obese adolescents showed a decrease in FA values in areas of the brain including the amygdala, hippocampus, thalamus, cingulate gyrus, fornix, insula, putamen, orbital gyrus and bilateral hypothalamus. Several of these regions are involved in appetite regulation, impulse control, emotions and reward and pleasure in eating.
"The data reveal a pattern of involvement among brain regions that are important in the control of appetite and emotions," Bertolazzi said. "There was no region of higher FA in obese patients compared to the control group," she added.
The researchers hope that these findings will offer new tools to combat this global public health crisis.
"Childhood obesity has increased 10 to 40 percent in the last 10 years in most countries," Bertolazzi said. "If we are able to identify the brain changes associated with obesity, this DTI technique could be used to help prevent obesity and avoid the complications associated with the condition."
https://www.sciencedaily.com/releases/2017/11/171130090044.htm
Eating disorder treatments need to consider social, cultural implications of the illness
November 13, 2017
Science Daily/University of East Anglia
People in treatment for eating disorders are poorly served when it comes to addressing the cultural aspects of eating problems, according to new research. This emerges as part of an overall set of findings that suggest contemporary eating disorder (ED) treatment in the UK pays little attention to the cultural contexts for eating problems, such as gender.
This emerges as part of an overall set of findings that suggest contemporary eating disorder (ED) treatment in the UK pays little attention to the cultural contexts for eating problems, such as gender. Although EDs affect people across different genders, ethnicities and ages, women and girls are disproportionately affected by eating problems.
But this quite obvious connection between eating disorders and cultural expectations surrounding femininity is woefully neglected in much treatment, said lead researcher Dr Su Holmes, a reader in UEA's School of Art, Media and American Studies. The research is published in the journal Eating Disorders.
Dr Holmes said that although there is now extensive evidence on how EDs are bound up with cultural ideas surrounding gender, the contemporary focus on evidence-based treatment, and particularly the rise of cognitive behavioural therapy (CBT), has all but forced these issues off the agenda. If cultural elements are addressed, it is through a limited focus on 'body image' work, which often invokes the significance of the media in perpetuating unattainable images of the body.
The paper said more culturally-focused perspectives on eating problems have argued that 'disordered eating may not necessarily be motivated by the drive for pursuit of thinness or any "distortion" of body image, but rather by wider experiences' of gender expectations and pressures.'
Dr Holmes' previous research with people who had received treatment for an ED showed that even when a patient specifically asks to talk about questions of gender, their request may be ignored -- either because such issues are seen as a low priority, or because health professionals have little training in this sphere.
In response to this, Dr Holmes and Ms Sarah Drake, an occupational therapist and lecturer in the School of Health and Social Care at UEA, devised and ran a new treatment intervention at an inpatient clinic that specialises in the treatment of EDs.
The group, which was run over 10 weeks at Newmarket House clinic Norwich, was called 'Cultural Approaches to Eating Disorders', and included all the patients who were resident in the clinic at the time. These were all female, with a diagnosis of anorexia, and their ages ranged from 19-51.
Each week, the programme examined what role culture might play in EDs, including:
· Gendered constructions of appetite
· Cultural expectations surrounding female emotion and anger
· 'Reading' the starved body in relation to cultural prescriptions of femininity
· The dynamics of 'healthy' eating/living and fitness cultures' aimed at women
The group used media, such as television adverts, Disney films, press articles, image bank photography to social media, to stimulate debate about the particular issue being explored. But the media were not consistently positioned as the 'cause' of anorexia, as so often happens in suggestions of how society influences eating problems. The study found that people living with EDs find that the tendency to portray women with anorexia as the passive victims of media influence is often seen as patronising and simplistic by those living with the illness.
One patient said that suggesting seeing "a skinny model in a magazine" influenced the development of EDs "completely trivialises" the many reasons people develop body- and eating distress.
Looking at the wider contexts that shape ideas about gender in society -- such as beliefs about 'appetite' -- was seen as helpful by the participants. This focus took in food advertising aimed at women as well as wider ideas about 'appetite', such as the ways in which girls and women are still expected to exercise more restraint in sexual appetite than boys and men -- and are sex- or slut-shamed if they don't.
Participants in the group said they found it useful to situate their problem within society, thus moving away from the more individualised focus of medical perspectives that may encourage self-blame -- but it also raised questions about recovery.
One patient said: "But then, as the groups went on it's like OK, maybe this society's norms are quite disordered. But then it's like ... if society's norms are disordered ... then ... I don't know, how am I meant to change kind of things?"
Dr Holmes said: "The medical framework may offer the patient a greater sense of personal agency when it comes to feelings of control in recovery. Given that anorexia in particular is seen to be tightly intertwined with issues of control, this is clearly worth some thought."
The research shows, however, that there is room for more work and exploration in this area, and the group is now being re-run with the hope of adapting it for other services in the region.
Dr Holmes said: "It is important to stress that the study does not work on the assumption that issues concerning gender identity are only relevant to the experience and treatment of eating disorders in girls and women. The focus on how eating- and body distress may be used to negotiate dominant ideas about gender and sexuality is similarly applicable to male patients, as well as gender minorities, even whilst the cultural constructions at stake may be different."
Indeed, she said, given that recent research indicates how transgender individuals may be particularly at risk from developing eating problems, this arguably adds credence to the idea that EDs may be bound up with the pressures and difficulties posed by dominant gender norms.
Dr Holmes said: "The bottom line is that, although eating disorders are now widely recognised as being shaped by biological, psychological and social factors, the social aspect of the equation is poorly served."
Get more information at: https://ueaeprints.uea.ac.uk/64112/
https://www.sciencedaily.com/releases/2017/11/171113095529.htm
Junk food almost twice as distracting as healthy food
October 26, 2017
Science Daily/Johns Hopkins University
When we haven't eaten, junk food is twice as distracting as healthy food or non-food items.
Even when people are hard at work, pictures of cookies, pizza and ice cream can distract them -- and these junk food images are almost twice as distracting as health food pictures, concludes a new Johns Hopkins University study, which also found that after a few bites of candy, people found junk food no more interesting than kale.
The study, which underscores people's implicit bias for fatty, sugary foods, and confirms the old adage that you shouldn't grocery shop hungry, is newly published online by the journal Psychonomic Bulletin and Review.
"We wanted to see if pictures of food, particularly high-fat, high-calorie food, would be a distraction for people engaged in a complicated task, said co-author Howard Egeth, a professor in the Department of Psychological and Brain Sciences. "So we showed them carrots and apples, and it slowed them down. We showed them bicycles and thumb tacks, and it slowed them down. But when we showed them chocolate cake and hot dogs, these things slowed them down about twice as much."
First, Egeth and lead author Corbin A. Cunningham, Distinguished Science of Learning Fellow in the Department of Psychological and Brain Sciences, created a complicated computer task, in which food was irrelevant, and asked a group of participants to find the answers as quickly as possible. As the participants worked diligently, pictures flashed in the periphery of the screen -- visible for only 125 milliseconds, which is too quick for people to fully realize what they just saw. The pictures were a mix of images of high-fat, high-calorie foods, healthy foods, or items that weren't food.
All of the pictures distracted people from the task, but Cunningham and Egeth found things like doughnuts, potato chips, cheese and candy were about twice as distracting. The healthy food pictures -- like carrots, apples and salads -- were no more distracting to people than non-foods like bicycles, lava lamps and footballs.
Next, the researchers recreated the experiment, but had a new group of participants eat two fun-sized candy bars before starting the computer work.
The researchers were surprised to find that after eating the chocolate, people weren't distracted by the high-fat, high-calorie food images any more than by healthy foods or other pictures.
The researchers wonder now if less chocolate or even other snacks would have the same effect.
"I assume it was because it was a delicious, high-fat, chocolatey snack," Egeth said. "But what if we gave them an apple? What if we gave them a zero-calorie soda? What if we told the subjects they'd get money if they performed the task quickly, which would be a real incentive not to get distracted. Could junk food pictures override even that?"
Cunningham said the results strikingly demonstrate that even when food is entirely irrelevant, and even when people think they're working hard and concentrating, food has the power to sneak in and grab our attention -- at least until we eat a little of it.
"What your grandmother might have told you about not going to the grocery store hungry seems to be true," Cunningham said. "You would probably make choices that you shouldn't or ordinarily wouldn't."
https://www.sciencedaily.com/releases/2017/10/171026135327.htm
Physical inactivity and restless sleep exacerbate genetic risk of obesity
Findings reported at ASHG 2017 Annual Meeting
October 20, 2017
Science Daily/American Society of Human Genetics
Low levels of physical activity and inefficient sleep patterns intensify the effects of genetic risk factors for obesity, according to new results.
Andrew Wood, PhD, postdoctoral researcher, who presented the work; Timothy Frayling, PhD, Professor; and their colleagues at the University of Exeter Medical School study the genetics of body mass index (BMI) and Type 2 Diabetes. In the past, Dr. Frayling explained, it has been difficult to measure interactions between genetic risk factors and aspects of environment and lifestyle in a systematic way.
"Until recently, physical activity and sleep patterns could not be measured with as much precision as genetic variants, and we relied on diaries or self-report, which can be very subjective," Dr. Frayling said. In contrast, the new study made use of wrist accelerometer data, which is more objective and quantifiable, and a large genetic dataset from about 85,000 UK Biobank participants aged 40 to 70.
"We wanted to find out if obesity-related genes and activity level have an interactive effect on obesity risk -- if there is a 'double whammy' effect of being both at genetic risk and physically inactive, beyond the additive effect of these factors," said Dr. Wood. The researchers computed a genetic risk score for each participant based on 76 common variants known to be associated with elevated risk of obesity, and analyzed this score in the context of accelerometer data and participants' BMIs.
They found the strongest evidence to date of a modest gene-activity interaction. For example, for a person of average height with 10 genetic variants associated with obesity, that genetic risk accounted for a 3.6 kilogram increase in weight among those who were less physically active but just 2.8 kilograms among those who were more active. Results were similar in analyses of sleep patterns; among participants with some genetic risk of obesity, those who woke up frequently or slept more restlessly had higher BMIs than those who slept more efficiently.
The researchers are currently examining whether this interaction between genetics and physical activity differs between men and women. They are also studying the effects of patterns of activity -- for example, whether a consistent level of moderate activity has different effects from overall low levels punctuated by periods of vigorous activity.
"We hope these findings will inform clinicians who help people lose or maintain their weight, and contribute to the understanding that obesity is complex and its prevention may look different for different people," said Dr. Frayling. "Ultimately, with further research, we may have the scope to personalize obesity interventions," he said.
https://www.sciencedaily.com/releases/2017/10/171020092240.htm
A spoonful of oil: Fats and oils help to unlock full nutritional benefits of veggies
October 9, 2017
Science Daily/Iowa State University
Some dressing with your greens may help you absorb more nutrients, according to a new study. The research found enhanced absorption of multiple fat-soluble vitamins in addition to beta-carotene and three other carotenoids. The results may ease the guilt of countless dieters who fret about adding dressing to their salads.
The song says a spoonful of sugar helps the medicine go down, but an Iowa State University scientist has published new research suggesting a spoonful of oil makes vegetables more nutritious.
A new study led by Wendy White, an associate professor of food science and human nutrition, shows that eating salad with added fat in the form of soybean oil promotes the absorption of eight different micronutrients that promote human health. Conversely, eating the same salad without the added oil lessens the likelihood that the body will absorb the nutrients.
The study appeared recently in the peer-reviewed American Journal of Clinical Nutrition, and the results may ease the guilt of countless dieters who fret about adding dressing to their salads.
White's study found added oil aided in the absorption of seven different micronutrients in salad vegetables. Those nutrients include four carotenoids -- alpha and beta carotene, lutein and lycopene -- two forms of vitamin E and vitamin K. The oil also promoted the absorption of vitamin A, the eighth micronutrient tracked in the study, which formed in the intestine from the alpha and beta carotene. The new study builds on previous research from White's group that focused on alpha and beta carotene and lycopene.
White said better absorption of the nutrients promotes a range of health benefits, including cancer prevention and eyesight preservation.
The study also found that the amount of oil added to the vegetables had a proportional relationship with the amount of nutrient absorption. That is, more oil means more absorption.
"The best way to explain it would be to say that adding twice the amount of salad dressing leads to twice the nutrient absorption," White said.
That doesn't give salad eaters license to drench their greens in dressing, she cautioned. But she said consumers should be perfectly comfortable with the U.S. dietary recommendation of about two tablespoons of oil per day.
The study included 12 college-age women who consumed salads with various levels of soybean oil, a common ingredient in commercial salad dressings. The subjects then had their blood tested to measure the absorption of nutrients. Women were chosen for the trial due to differences in the speed with which men and women metabolize the nutrients in question.
The results showed maximal nutrient absorption occurred at around 32 grams of oil, which was the highest amount studied, or a little more than two tablespoons. However, White said she found some variability among the subjects.
"For most people, the oil is going to benefit nutrient absorption," she said. "The average trend, which was statistically significant, was for increased absorption."
Research collaborators include Yang Zhou, a former ISU postdoctoral researcher; Agatha Agustiana Crane, a former graduate research assistant in food science and human nutrition; Philip Dixon, a University Professor of Statistics, and Frits Quadt of Quadt Consultancy, among others.
Unilever, a global food company, provided funding for the research. The company had no input in the publication of the study.
So a spoonful or two of salad dressing may indeed help you derive the optimal nutritional benefit from your veggies. The relationship between a spoonful of sugar and the medicine going down, however, remains outside the scope of White's research.
https://www.sciencedaily.com/releases/2017/10/171009124026.htm
More daytime sleepiness, more Alzheimer's risk?
Excessive daytime sleepiness linked with brain protein involved in memory-robbing disease
September 6, 2018
Science Daily/Johns Hopkins University Bloomberg School of Public Health
Analysis of data captured during a long-term study of aging adults shows that those who report being very sleepy during the day were nearly three times more likely than those who didn't to have brain deposits of beta amyloid, a protein that's a hallmark for Alzheimer's disease, years later.
The finding, reported Sept. 5 in the journal SLEEP, adds to a growing body of evidence that poor quality sleep could encourage this form of dementia to develop, suggesting that getting adequate nighttime sleep could be a way to help prevent Alzheimer's disease.
"Factors like diet, exercise and cognitive activity have been widely recognized as important potential targets for Alzheimer's disease prevention, but sleep hasn't quite risen to that status -- although that may well be changing," says Adam P. Spira, PhD, associate professor in the Department of Mental Health at the Johns Hopkins Bloomberg School of Public Health. Spira led the study with collaborators from the National Institute on Aging (NIA), the Bloomberg School and Johns Hopkins Medicine.
"If disturbed sleep contributes to Alzheimer's disease," he adds, "we may be able to treat patients with sleep issues to avoid these negative outcomes."
The study used data from the Baltimore Longitudinal Study of Aging (BLSA), a long-term study started by the NIA in 1958 that followed the health of thousands of volunteers as they age. As part of the study's periodic exams, volunteers filled a questionnaire between 1991 and 2000 that asked a simple yes/no question: "Do you often become drowsy or fall asleep during the daytime when you wish to be awake?" They were also asked, "Do you nap?" with response options of "daily," "1-2 times/week," "3-5 times/week," and "rarely or never."
A subgroup of BLSA volunteers also began receiving neuroimaging assessments in 1994. Starting in 2005, some of these participants received positron emission tomography (PET) scans using Pittsburgh compound B (PiB), a radioactive compound that can help identify beta-amyloid plaques in neuronal tissue. These plaques are a hallmark of Alzheimer's disease.
The researchers identified 123 volunteers who both answered the earlier questions and had a PET scan with PiB an average of nearly 16 years later. They then analyzed this data to see if there was a correlation between participants who reported daytime sleepiness or napping and whether they scored positive for beta-amyloid deposition in their brains.
Before adjusting for demographic factors that could influence daytime sleepiness, such as age, sex, education, and body-mass index, their results showed that those who reported daytime sleepiness were about three times more likely to have beta-amyloid deposition than those who didn't report daytime fatigue. After adjusting for these factors, the risk was still 2.75 times higher in those with daytime sleepiness.
The unadjusted risk for amyloid-beta deposition was about twice as high in volunteers who reported napping, but this did not reach statistical significance.
It's currently unclear why daytime sleepiness would be correlated with the deposition of beta-amyloid protein, Spira says. One possibility is that daytime sleepiness itself might somehow cause this protein to form in the brain. Based on previous research, a more likely explanation is that disturbed sleep -- due to obstructive sleep apnea, for example -- or insufficient sleep due to other factors, causes beta-amyloid plaques to form through a currently unknown mechanism, and that these sleep disturbances also cause excessive daytime sleepiness.
"However, we cannot rule out that amyloid plaques that were present at the time of sleep assessment caused the sleepiness," he added.
Animal studies in Alzheimer's disease models have shown that restricting nighttime sleep can lead to more beta-amyloid protein in the brain and spinal fluid. A handful of human studies have linked poor sleep with greater measures of beta-amyloid in neuronal tissue.
Researchers have long known that sleep disturbances are common in patients diagnosed with Alzheimer's disease -- caregiver stress from being up with patients at night is a leading reason for Alzheimer's disease patients to be placed in long-term care, Spira explains. Growing beta-amyloid plaques and related brain changes are thought to negatively affect sleep.
But this new study adds to growing evidence that poor sleep might actually contribute to Alzheimer's disease development, Spira adds. This suggests that sleep quality could be a risk factor that's modifiable by targeting disorders that affect sleep, such as obstructive sleep apnea and insomnia, as well as social- and individual-level factors, such as sleep loss due to work or binge-watching TV shows.
"There is no cure yet for Alzheimer's disease, so we have to do our best to prevent it. Even if a cure is developed, prevention strategies should be emphasized," Spira says. "Prioritizing sleep may be one way to help prevent or perhaps slow this condition."
https://www.sciencedaily.com/releases/2018/09/180906141501.htm
Measure of belly fat in older adults is linked with cognitive impairment
August 1, 2018
Science Daily/Trinity College Dublin
Data from over 5,000 adults over the age of 60 indicates that as waist:hip ratio increases, so does cognitive impairment. The findings have significant implications as the global prevalence of dementia is predicted to increase from 24.3 million in 2001 to 81.1 million by 2040.
Previous studies have found that people who are overweight do not perform as well on tests of memory and visuospatial ability compared to those who are normal weight. However, it is not well known if this is true in older adults. This is of concern within Ireland, as over half of the over 50s population is classified as being centrally obese, with only 16% of men and 26% of women reported to have a BMI (body mass index) within the normal range.
The researchers used data from the Trinity Ulster Department of Agriculture (TUDA) ageing cohort study comprising, which is a cross-border collaborative research project gathering data from thousands of elderly adults in Northern Ireland and Ireland.
The researchers found that a higher waist:hip ratio was associated with reduced cognitive function. This could be explained by an increased secretion of inflammatory markers by belly fat, which has been previously associated with a higher risk of impaired cognition. On the contrary, body mass index (BMI) was found to protect cognitive function. BMI is a crude measure of body fat and cannot differentiate between fat and fat-free mass (muscle), thus it is proposed that the fat-free mass component is likely to be the protective factor.
To the best of the authors' knowledge, this is one of the largest studies of older adults to report these findings. Given the high prevalence of overweight and obesity in the older population and the economic and social burden of cognitive dysfunction, the results suggest that reducing obesity and exposure to obeso-genic risk factors could offer a cost-effective public health strategy for the prevention of cognitive decline.
Clinical Associate Professor in Medical Gerontology at Trinity, Conal Cunningham, is the senior author of the study. He said: "While we have known for some time that obesity is associated with negative health consequences our study adds to emerging evidence suggesting that obesity and where we deposit our excess weight could influence our brain health. This has significant public health implications."
https://www.sciencedaily.com/releases/2018/08/180801115257.htm
Overnight brain stimulation improves memory
Non-invasive technique enhances memory storage without disturbing sleep
July 23, 2018
Science Daily/Society for Neuroscience
New research in humans demonstrates the potential to improve memory with a non-invasive brain stimulation technique delivered during sleep. The results come from a project that aims to better understand the process of memory consolidation, which could translate into improved memory function in both healthy and patient populations.
The transfer of memories from the hippocampus to the neocortex for long-term storage is thought to be enabled by synchronization of these parts of the brain during sleep. Nicholas Ketz, Praveen Pilly, and colleagues at University of New Mexico sought to enhance this natural process of overnight reactivation or neural replay to improve memory with a closed-loop transcranial alternating current stimulation system matching the phase and frequency of ongoing slow-wave oscillations during sleep.
Participants were trained and tested on a realistic visual discrimination task in which they had to detect potentially threatening hidden objects and people such as explosive devices and enemy snipers. The researchers found that when participants received stimulation during overnight visits to their sleep laboratory, they showed improved performance in detecting targets in similar but novel situations the next day compared to when they did not receive the stimulation, suggesting an integration of recent experience into a more robust and general memory.
Overnight memory changes correlated with stimulation-induced neural changes, which could be used to optimize stimulation in future applications.
These findings provide a method for enhancing memory consolidation without disturbing sleep.
https://www.sciencedaily.com/releases/2018/07/180723142907.htm
Treating dementia with the healing waves of sound
Ultrasound applied to brain could help treat patients with dementia
July 20, 2018
Science Daily/Tohoku University
Ultrasound waves applied to the whole brain improve cognitive dysfunction in mice with conditions simulating vascular dementia and Alzheimer's disease. It is possible that this type of therapy may also benefit humans.
The team, led by cardiologist Hiroaki Shimokawa, found that applying low-intensity pulsed ultrasound (LIPUS) to the whole brain of the mice improved blood vessel formation and nerve cell regeneration without having obvious side effects.
"The LIPUS therapy is a non-invasive physiotherapy that could apply to high-risk elderly patients without the need for surgery or anaesthesia, and could be used repeatedly," says Shimokawa.
Dementia affects about 50 million people worldwide, with 10 million new cases occurring every year. But there are currently no curative treatments available for vascular dementia or Alzheimer's disease, the most common causes of dementia. Also, the cells lining the brain's blood vessels are tightly packed, forming a blood-brain barrier that prevents large molecules from crossing into the brain tissue. This limits the types of drugs and cell therapies that could be made available to treat dementia.
Shimokawa and his team had conducted previous studies showing that LIPUS improved blood vessel formation in pigs with myocardial ischemia, a condition where there is reduced blood flow to the heart. Other studies have reported that LIPUS increases the production of proteins involved in nerve cell survival and growth, in addition to a role in promoting nerve regeneration. Focusing LIPUS treatment on a region in the brain called the hippocampus, which is involved in memory, has also been found to improve dementia in mice, but the details of how it does this need to be more fully investigated.
The Tohoku University team wanted to find out if whole-brain rather than focused LIPUS is effective in treating mouse models of dementia, and if it was, what was happening at the molecular levels to achieve this.
They found that cognitive impairment markedly improved in mice with conditions similar to vascular dementia and Alzheimer's disease when LIPUS was applied to the whole brain three times a day for 20 minutes each time. The mice with vascular dementia received the treatment on the first, third and fifth days following a surgical procedure that limited the brain's blood supply. The mice with a condition simulating Alzheimer's disease in humans received 11 LIPUS treatments over a period of three months.
At the molecular level, genes related to the cells lining blood vessels were turned on. Also, there was increased expression of an enzyme involved in blood vessel formation and a protein involved in nerve cell survival and growth.
The researchers conclude that their study, recently published in the journal Brain Stimulation, provides the first experimental evidence that whole-brain LIPUS therapy markedly improves cognitive dysfunctions without serious side effects by enhancing specific cells related to dementia's pathology.
The first clinical trials to evaluate the effectiveness and safety of the LIPUS treatment are already underway.
https://www.sciencedaily.com/releases/2018/07/180720092507.htm
Sugar improves memory in over-60s, helping them work smarter
July 18, 2018
Science Daily/University of Warwick
Sugar improves memory in older adults -- and makes them more motivated to perform difficult tasks at full capacity -- according to new research.
Led by PhD student Konstantinos Mantantzis, Professor Elizabeth Maylor and Dr Friederike Schlaghecken in Warwick's Department of Psychology, the study found that increasing blood sugar levels not only improves memory and performance, but makes older adults feel happier during a task.
The researchers gave young (aged 18-27) and older (aged 65-82) participants a drink containing a small amount of glucose, and got them to perform various memory tasks. Other participants were given a placebo -- a drink containing artificial sweetener.
The researchers measured participants' levels of engagement with the task, their memory score, mood, and their own perception of effort.
They found that increasing energy through a glucose drink can help both young and older adults to try harder compared to those who had the artificial sweetener. For young adults, that's where it ended, though: glucose did not improve either their mood or their memory performance.
However, older adults who had a glucose drink showed significantly better memory and more positive mood compared to older adults who consumed the artificial sweetener.
Moreover, although objective measures of task engagement showed that older adults in the glucose group put more effort into the task than those who consumed the artificial sweetener, their own self-reports showed that they did not feel as if they had tried any harder.
The authors concluded that short-term energy availability in the form of raised blood sugar levels could be an important factor in older adults' motivation to perform a task at their highest capacity.
Heightened motivation, in turn, could explain the fact that increased blood sugar levels also increase older adults' sense of self-confidence, decrease self-perceptions of effort, and improve mood. However, more research is needed to disentangle these factors in order to fully understand how energy availability affects cognitive engagement, and to develop clear dietary guidelines for older adults.
Konstantinos Mantantzis, a PhD student from the University of Warwick's Department of Psychology, commented:
"Over the years, studies have shown that actively engaging with difficult cognitive tasks is a prerequisite for the maintenance of cognitive health in older age. Therefore, the implications of uncovering the mechanisms that determine older adults' levels of engagement cannot be understated."
Dr Friederike Schlaghecken, from the University of Warwick's Department of Psychology, commented:
"Our results bring us a step closer to understanding what motivates older adults to exert effort and finding ways of increasing their willingness to try hard even if a task seems impossible to perform."
https://www.sciencedaily.com/releases/2018/07/180718104747.htm
Majority of older adults with probable dementia are likely unaware they have it
Less education and unaccompanied medical visits linked to lack of formal diagnosis or awareness of diagnosis
July 17, 2018
Science Daily/Johns Hopkins Medicine
An analysis of information gathered for an ongoing and federally sponsored study of aging and disability adds to evidence that a substantial majority of older adults with probable dementia in the United States have never been professionally diagnosed or are unaware they have been.
A Johns Hopkins Medicine analysis of information gathered for an ongoing and federally sponsored study of aging and disability adds to evidence that a substantial majority of older adults with probable dementia in the United States have never been professionally diagnosed or are unaware they have been.
A report of the findings was published in the July issue of the Journal of General Internal Medicine. Most of the findings, the researchers say, confirm previous similar estimates, but unaccompanied visits to a doctor or clinic emerged as a newly strong risk factor for lack of formal diagnosis or awareness of diagnosis.
"There is a huge population out there living with dementia who don't know about it," says Halima Amjad, M.D., M.P.H., assistant professor of medicine at the Johns Hopkins University School of Medicine and the study's lead author. "The implications are potentially profound for health care planning and delivery, patient-physician communication and much more," she says.
Overall, Amjad says, "If dementia is less severe and people are better able to perform day-to-day tasks independently, symptoms of cognitive loss are more likely masked, especially for patients who visit the doctor without a family member or friend who may be more aware of the patient's symptoms."
An estimated 5.7 million people in the United States live with dementia, according to the Alzheimer's Association, but only half of those have a documented, official diagnosis by a physician. Timely diagnosis is important for maintaining or improving health and planning care, says Amjad, so it's important to identify which populations are less likely to be diagnosed or less likely to be aware of their diagnosis.
Building on previous research, which identified activities and living conditions linked to dementia diagnosis, Amjad sought this time to pinpoint at-risk populations nationwide.
To do so, Amjad and the research team drew on data from the National Health and Aging Trends Study, an ongoing study of Medicare recipients ages 65 and older across the United States, and selected those who met criteria for probable dementia in 2011 and had three years of continuous fee-for-service Medicare claims before 2011. The latter information helped the researchers determine whether participants' physicians had billed for dementia diagnosis and/or care.
The research team identified 585 such adults and examined demographic data such as highest level of education attained, race/ethnicity and income, as well as data on whether participants were able to perform activities such as laundry, shopping or cooking on their own.
Among those with probable dementia, 58.7 percent were determined to be either undiagnosed (39.5 percent) or unaware of their diagnosis (19.2 percent).
Participants who were Hispanic, had less than a high school education, attended medical visits alone or were deemed more able to perform daily tasks were more likely to be undiagnosed. Specifically, those with at least a high school education had a 46 percent lower chance of being undiagnosed compared with those who had less education; and those who attended medical visits alone were twice as likely to be undiagnosed than those who were accompanied.
Participants who were diagnosed but unaware of their diagnosis had less education, attended visits alone more often and had fewer functional impairments. Those with at least a high school education had a 58 percent lower chance of being unaware compared with those who had less education. Those who attended medical visits alone were about twice as likely to be unaware than those who were accompanied. Each activity impairment decreased the chance of being unaware of diagnosis by 28 percent.
While Amjad acknowledges that the study is limited by potentially inaccurate self-reporting of dementia diagnoses, possible discrepancies between medical record documentation and billing codes, and the use of older data, she says the findings will likely help physicians be more alert to people who may need more careful screening.
"There are subsets of people doctors can focus on when implementing cognitive screening, such as minorities, those with lower levels of education and those who come in by themselves," says Amjad.
Looking forward, Amjad plans to study whether documentation of a dementia diagnosis is meaningful if patients and family members don't understand what a diagnosis means.
https://www.sciencedaily.com/releases/2018/07/180717094726.htm
Every person has a unique brain anatomy
July 10, 2018
Science Daily/University of Zurich
Like with fingerprints, no two people have the same brain anatomy, a study has shown. This uniqueness is the result of a combination of genetic factors and individual life experiences.
The fingerprint is unique in every individual: As no two fingerprints are the same, they have become the go-to method of identity verification for police, immigration authorities and smartphone producers alike. But what about the central switchboard inside our heads? Is it possible to find out who a brain belongs to from certain anatomical features? This is the question posed by the group working with Lutz Jäncke, UZH professor of neuropsychology. In earlier studies, Jäncke had already been able to demonstrate that individual experiences and life circumstances influence the anatomy of the brain.
Experiences make their mark on the brain
Professional musicians, golfers or chess players, for example, have particular characteristics in the regions of the brain which they use the most for their skilled activity. However, events of shorter duration can also leave behind traces in the brain: If, for example, the right arm is kept still for two weeks, the thickness of the brain's cortex in the areas responsible for controlling the immobilized arm is reduced. "We suspected that those experiences having an effect on the brain interact with the genetic make-up so that over the course of years every person develops a completely individual brain anatomy," explains Jäncke.
Magnetic resonance imaging provides basis for calculations
To investigate their hypothesis, Jäncke and his research team examined the brains of nearly 200 healthy older people using magnetic resonance imaging three times over a period of two years. Over 450 brain anatomical features were assessed, including very general ones such as total volume of the brain, thickness of the cortex, and volumes of grey and white matter. For each of the 191 people, the researchers were able to identify an individual combination of specific brain anatomical characteristics, whereby the identification accuracy, even for the very general brain anatomical characteristics, was over 90 percent.
Combination of circumstances and genetics
"With our study we were able to confirm that the structure of people's brains is very individual," says Lutz Jäncke on the findings. "The combination of genetic and non-genetic influences clearly affects not only the functioning of the brain, but also its anatomy." The replacement of fingerprint sensors with MRI scans in the future is unlikely, however. MRIs are too expensive and time-consuming in comparison to the proven and simple method of taking fingerprints.
Progress in neuroscience
An important aspect of the study's findings for Jäncke is that they reflect the great developments made in the field in recent years: "Just 30 years ago we thought that the human brain had few or no individual characteristics. Personal identification through brain anatomical characteristics was unimaginable." In the meantime magnetic resonance imaging has got much better, as has the software used to evaluate digitalized brain scans -- Jäncke says it is thanks to this progress that we now know better.
https://www.sciencedaily.com/releases/2018/07/180710104631.htm
Sleep disorder linked with changes to brain structure typical of dementia
July 4, 2018
Science Daily/European Lung Foundation
Obstructive sleep apnea is associated with changes to the structure of the brain that are also seen in the early stages of dementia, according to a new study.
OSA, where the walls of the throat relax and narrow during sleep stopping breathing, is known to reduce levels of oxygen in the blood. The new study suggests that this drop in oxygen may be linked to a shrinking of the brain's temporal lobes and a corresponding decline in memory.
The researchers say the study provides evidence that screening older people for OSA and giving treatment where needed could help prevent dementia in this population.
The study was led by Professor Sharon Naismith from the University of Sydney, Australia. She said: "Between 30 and 50% of the risk for dementia is due to modifiable factors, such as depression, high blood pressure, obesity and smoking. In recent years, researchers have recognised that various sleep disturbances are also risk factors for dementia. We wanted to look specifically at obstructive sleep apnoea and its effects on the brain and cognitive abilities."
The researchers worked with a group of 83 people, aged between 51 and 88 years, who had visited their doctor with concerns over their memory or mood but had no OSA diagnosis. Each participant was assessed for their memory skills and symptoms of depression, and each was given an MRI scan to measure the dimensions of different areas of the brain.
Participants also attended a sleep clinic where they were monitored overnight for signs of OSA using polysomnography. This technique records brain activity, levels of oxygen in the blood, heart rate, breathing and movements.
The researchers found that patients who had low levels of oxygen in their blood while they were sleeping tended to have reduced thickness in the left and right temporal lobes of the brain. These are regions known to be important in memory and affected in dementia.
They also found that this alteration in the brain was linked with participant's poorer ability to learn new information. The researchers say this is the first time a direct link of this kind has been shown.
Conversely, patients with signs of OSA were also more likely to have increased thickness in other regions of the brain, which the researchers say could be signs of the brain reacting to lower levels of oxygen with swelling and inflammation.
OSA is more common in older people and has already been linked with heart disease, stroke and cancer, but it can be treated with a continuous positive airway pressure (CPAP) device, which prevents the airway closing during sleep.
Professor Naismith added: "We chose to study this group because they are older and considered at risk of dementia. Our results suggest that we should be screening for OSA in older people. We should also be asking older patients attending sleep clinics about their memory and thinking skills, and carrying out tests where necessary.
"There is no cure for dementia so early intervention is key. On the other hand, we do have an effective treatment for OSA. This research shows that diagnosing and treating OSA could be an opportunity to prevent cognitive decline before it's too late."
Professor Naismith and her team are now working on research to find out whether CPAP treatment can prevent further cognitive decline and improve brain connectivity in patients with mild cognitive impairment.
Andrea Aliverti, Professor of Bioengineering at Politecnico di Milano, Italy, is Head of the European Respiratory Society's Assembly on Clinical Physiology and Sleep and was not involved in the research. He said: "We already know that as well as disrupting sleep, OSA can increase the risk of high blood pressure, type 2 diabetes, heart attack and stroke. This research adds to evidence that OSA is also linked to dementia and suggests a likely mechanism for the link. However, we can treat OSA and measures such as stopping smoking and losing weight can reduce the risk of developing the condition."
https://www.sciencedaily.com/releases/2018/07/180704194350.htm
Brain study paves way for therapy for common cause of dementia
July 4, 2018
Science Daily/University of Edinburgh
Scientists have uncovered a potential approach to treat one of the commonest causes of dementia and stroke in older people. Studies with rats found the treatment can reverse changes in blood vessels in the brain associated with the condition, called cerebral small vessel disease. Treatment also prevents damage to brain cells caused by these blood vessel changes, raising hope that it could offer a therapy for dementia.
Studies with rats found the treatment can reverse changes in blood vessels in the brain associated with the condition, called cerebral small vessel disease.
Treatment also prevents damage to brain cells caused by these blood vessel changes, raising hope that it could offer a therapy for dementia.
Small vessel disease, or SVD, is a major cause of dementia and can also worsen the symptoms of Alzheimer's disease. It is responsible for almost half of all dementia cases in the UK and is a major cause of stroke, accounting for around one in five cases.
Patients with SVD are diagnosed from brain scans, which detect damage to white matter -- a key component of the brain's wiring.
Until now, it was not known how changes in small blood vessels in the brain associated with SVD can cause damage to brain cells.
A team led by the University of Edinburgh found that SVD occurs when cells that line the small blood vessels in the brain become dysfunctional. This causes them to secrete a molecule into the brain.
The molecule stops production of the protective layer that surrounds brain cells -- called myelin -- which leads to brain damage.
Treating rats with drugs that stop blood vessel cells from becoming dysfunctional reversed the symptoms of SVD and prevented brain damage, tests found.
Researchers say that further studies will need to test whether the treatment also works when the disease is firmly established. They will also need to check if the treatment can reverse the symptoms of dementia.
Dementia is one of the biggest problems facing society, as people live longer and the population ages. Estimates indicate there are almost 47 million people living with dementia worldwide and the numbers affected are expected to double every 20 years, rising to more than 115 million by 2050.
The research, published in Science Translational Medicine, was carried out at the Medical Research Council Centre for Regenerative Medicine and the UK Dementia Research Institute at the University of Edinburgh. It was funded by the MRC, Alzheimer's Research UK and Fondation Leducq.
Professor Anna Williams, Group Leader at the University of Edinburgh's MRC Centre for Regenerative Medicine, said: "This important research helps us understand why small vessel disease happens, providing a direct link between small blood vessels and changes in the brain that are linked to dementia. It also shows that these changes may be reversible, which paves the way for potential treatments."
Dr Sara Imarisio, Head of Research at Alzheimer's Research UK said: "Changes to the blood supply in the brain play an important role in Alzheimer's disease as well as being a direct cause of vascular dementia. This pioneering research highlights a molecular link between changes to small blood vessels in the brain and damage to the insulating 'white matter' that helps nerve cells to send signals around the brain.
"The findings highlight a promising direction for research into treatments that could limit the damaging effects of blood vessel changes and help keep nerve cells functioning for longer. There are currently no drugs that slow down or stop Alzheimer's disease and no treatments to help people living with vascular dementia. Alzheimer's Research UK is very pleased to have helped fund this innovative research, which is only possible thanks to the work of our dedicated supporters."
Dr Nathan Richardson, the MRC's Head of Molecular and Cellular Medicine, commented: "This study is a great example of how innovative discovery science into regenerative mechanisms can be applied to improve our understanding of how vascular changes contribute to dementia. This research in rats opens up new possibilities for developing therapies for cerebral small vessel disease."
https://www.sciencedaily.com/releases/2018/07/180704161504.htm
Fish's use of electricity might shed light on human illnesses
June 21, 2018
Science Daily/University of Texas at Austin
African weakly electric fish, commonly called baby whales, use incredibly brief electrical pulses to sense the world around them and communicate with other members of their species. Part of that electrical mechanism exists in humans -- and by studying these fish, scientists may unlock clues about conditions like epilepsy.
Deep in the night in muddy African rivers, a fish uses electrical charges to sense the world around it and communicate with other members of its species. Signaling in electrical spurts that last only a few tenths of a thousandth of a second allows the fish to navigate without letting predators know it is there. Now scientists have found that the evolutionary trick these fish use to make such brief discharges could provide new insights, with a bearing on treatments for diseases such as epilepsy.
In a new paper in the journal Current Biology, scientists led by a team at The University of Texas at Austin and Michigan State University outline how some fish, commonly referred to as baby whales, have developed a unique bioelectric security system that lets them produce incredibly fast and short pulses of electricity so they can communicate without jamming one another's signals, while also eluding the highly sensitive electric detection systems of predatory catfish."
In a specialized electric organ near the tail, weakly electric fish, like the baby whales, possess a protein that also exists in the hearts and muscles of humans. The electrical pulses generated through this protein, called the KCNA7 potassium ion channel, last just a few tenths of a thousandth of a second, and some electric fish have adapted to discriminate between timing differences in electrical discharges of less than 10 millionths of a second.
"Most fish cannot detect electric fields, but catfish sense them. The briefer electric fish can make their electric pulse, the more difficult it is for catfish to track them," said Harold Zakon, a professor in the departments of Integrative Biology and Neuroscience.
The team identified a negatively charged patch in the KCNA7 protein that allows the channel in the electric fish to open quickly and be more sensitive to voltage, allowing for the extremely brief discharges.
What scientists have learned about these fish, the electrical signals they use and how they evolved may help humans in the future by shedding light on how those same electrical pathways operate in conditions such as epilepsy, where electrical pulses in the brain and muscles cause seizures. The finding also may have implications for discoveries about migraines and some heart conditions.
"Mutations in potassium channels that make them too sensitive or not sensitive enough to electrical stimuli can lead to epilepsy or cardiac and muscle diseases," said Swapna Immani, first author of the paper and a research associate in neuroscience and integrative biology. "So understanding what controls the sensitivity of potassium channels to stimuli is important for health as well as a basic understanding of ion channels."
Previous understanding of the same protein was based on potassium channels in fruit flies, but researchers say this paper suggests that the particular region with the negative patch might function differently in vertebrates.
Looking at the evolution of the specialized electric organ also can provide important windows into how genes change and express themselves. By studying unique or extreme abilities in the animal kingdom, much can be learned about the genetic basis of adaptations, the paper says.
"The take-home message of our project is that strange animals like weakly electric fish can give very deep insights into nature, sometimes with important biomedical consequences," said Jason Gallant, assistant professor of integrative biology at Michigan State University and a researcher on the project. "We discovered something at first blush that would seem like an idiosyncrasy of the biology of electric fish, which is always exciting but lacks broad applicability. Because of the relaxed evolutionary constraints on this important potassium channel in electric fish, which don't have to follow the same rules normally imposed by nervous system or muscle, the tinkering of natural selection has revealed a physical 'rule' that we suspect governs potassium channels more broadly."
https://www.sciencedaily.com/releases/2018/06/180621141054.htm
Fundamental rule of brain plasticity
June 21, 2018
Science Daily/Picower Institute at MIT
A series of complex experiments in the visual cortex of mice has yielded a simple rule about plasticity: When a synapse strengthens, others immediately nearby weaken.
Our brains are famously flexible, or "plastic," because neurons can do new things by forging new or stronger connections with other neurons. But if some connections strengthen, neuroscientists have reasoned, neurons must compensate lest they become overwhelmed with input. In a new study in Science, researchers at the Picower Institute for Learning and Memory at MIT demonstrate for the first time how this balance is struck: when one connection, called a synapse, strengthens, immediately neighboring synapses weaken based on the action of a crucial protein called Arc.
Senior author Mriganka Sur said he was excited but not surprised that his team discovered a simple, fundamental rule at the core of such a complex system as the brain, where 100 billion neurons each have thousands of ever-changing synapses. He likens it to how a massive school of fish can suddenly change direction, en masse, so long as the lead fish turns and every other fish obeys the simple rule of following the fish right in front of it.
"Collective behaviors of complex systems always have simple rules," said Sur, Paul E. and Lilah Newton Professor of Neuroscience in the Picower Institute and the department of Brain and Cognitive Sciences at MIT. "When one synapse goes up, within 50 micrometers there is a decrease in the strength of other synapses using a well-defined molecular mechanism."
This finding, he said, provides an explanation of how synaptic strengthening and weakening combine in neurons to produce plasticity.
Multiple manipulations
Though the rule they found was simple, the experiments that revealed it were not. As they worked to activate plasticity in the visual cortex of mice and then track how synapses changed to make that happen, lead authors Sami El-Boustani and Jacque Pak Kan Ip, postdoctoral researchers in Sur's lab, accomplished several firsts.
In one key experiment, they invoked plasticity by changing a neuron's "receptive field," or the patch of the visual field it responds to. Neurons receive input through synapses on little spines of their branch-like dendrites. To change a neuron's receptive field, the scientists pinpointed the exact spine on the relevant dendrite of the neuron, and then closely monitored changes in its synapses as they showed the mouse a target in a particular place on a screen that differed from the neuron's original receptive field. Whenever the target was in the new receptive field position they wanted to induce, they reinforced the neuron's response by flashing a blue light inside the mouse's visual cortex, instigating extra activity just like another neuron might. The neuron had been genetically engineered to be activated by light flashes, a technique called "optogenetics."
The researchers did this over and over. Because the light stimulation correlated with each appearance of the target in the new position in the mouse's vision, this caused the neuron to strengthen a particular synapse on the spine, encoding the new receptive field.
"I think it's quite amazing that we are able to reprogram single neurons in the intact brain and witness in the living tissue the diversity of molecular mechanisms that allows these cells to integrate new functions through synaptic plasticity," El-Boustani said.
As the synapse for the new receptive field grew, the researchers could see under the two-photon microscope that nearby synapses also shrank. They did not observe these changes in experimental control neurons that lacked the optogenetic stimulation.
But then they went further to confirm their findings. Because synapses are so tiny, they are near the limit of the resolution of light microscopy. So after the experiments the team dissected the brain tissues containing the dendrites of manipulated and control neurons and shipped them to co-authors at the Ecole Polytechnique Federal de Lausanne in Switzerland. They performed a specialized, higher-resolution, 3D electron microscope imaging, confirming that the structural differences seen under the two-photon microscope were valid.
"This is the longest length of dendrite ever reconstructed after being imaged in vivo," said Sur, who also directs the Simons Center for the Social Brain at MIT.
Of course, reprogramming a mouse's genetically engineered neuron with flashes of light is an unnatural manipulation, so the team did another more classic "monocular deprivation" experiment in which they temporarily closed one eye of a mouse. When that happens synapses in neurons related to the closed eye weaken and synapses related to the still open eye strengthen. Then when they reopened the previously closed eye, the synapses rearrange again. They tracked that action, too, and saw that as synapses strengthen, their immediate neighbors would weaken to compensate.
Solving the mystery of the Arc
Having seen the new rule in effect, the researchers were still eager to understand how neurons obey it. They used a chemical tag to watch how key "AMPA" receptors changed in the synapses and saw that synaptic enlargement and strengthening correlated with more AMPA receptor expression while shrinking and weakening correlated with less AMPA receptor expression.
The protein Arc regulates AMPA receptor expression, so the team realized they had to track Arc to fully understand what was going on. The problem, Sur said, is that no one had ever done that before in the brain of a live, behaving animal. So the team reached out to co-authors at the Kyoto University Graduate School of Medicine and the University of Tokyo, who invented a chemical tag that could do so.
Using the tag, the team could see that the strengthening synapses were surrounded with weakened synapses that had enriched Arc expression. Synapses with reduced amount of Arc were able to express more AMPA receptors whereas increased Arc in neighboring spines caused those synapses to express less AMPA receptors.
"We think Arc maintains a balance of synaptic resources," Ip said. "If something goes up, something must go down. That's the major role of Arc."
Sur said the study therefore solves a mystery of Arc: No one before had understood why Arc seemed to be upregulated in dendrites undergoing synaptic plasticity, even though it acts to weaken synapses, but now the answer was clear. Strengthening synapses increase Arc to weaken their neighbors.
Sur added that the rule helps explain how learning and memory might work at the individual neuron level because it shows how a neuron adjusts to the repeated simulation of another.
https://www.sciencedaily.com/releases/2018/06/180621141027.htm
Dementia can be caused by hypertension
June 13, 2018
Science Daily/Oxford University Press USA
A new study indicates that patients with high blood pressure are at a higher risk of developing dementia. This research also shows (for the first time) that an MRI can be used to detect very early signatures of neurological damage in people with high blood pressure, before any symptoms of dementia occur.
High blood pressure is a chronic condition that causes progressive organ damage. It is well known that the vast majority of cases of Alzheimer's disease and related dementia are not due to genetic predisposition but rather to chronic exposure to vascular risk factors.
The clinical approach to treatment of dementia patients usually starts only after symptoms are clearly evident. However, it has becoming increasingly clear that when signs of brain damage are manifest, it may be too late to reverse the neurodegenerative process. Physicians still lack procedures for assessing progression markers that could reveal pre-symptomatic alterations and identify patients at risk of developing dementia.
Researchers screened subjects admitted at the Regional Excellence Hypertension Center of the Italian Society of Hypertension in the Department of Angiocardioneurology and Translational Medicine of the I.R.C.C.S, Neuromed, in Italy. Researchers recruited people aged 40 to 65, compliant to give written informed consent and with the possibility to perform a dedicated 3 Tesla MRI scan.
This work was conducted on patients with no sign of structural damage and no diagnosis of dementia. All patients underwent clinical examination to determine their hypertensive status and the related target organ damage. Additionally, patients were subjected to an MRI scan to identify microstructural damage.
To gain insights in the neurocognitive profile of patients a specific group of tests was administered. As primary outcome of the study the researchers aimed at finding any specific signature of brain changes in white matter microstructure of hypertensive patients, associated with an impairment of the related cognitive functions.
The result indicated that hypertensive patients showed significant alterations in three specific white matter fiber-tracts. Hypertensive patients also scored significantly worse in the cognitive domains ascribable to brain regions connected through those fiber-tracts, showing decreased performances in executive functions, processing speed, memory and related learning tasks.
Overall, white matter fiber-tracking on MRIs showed an early signature of damage in hypertensive patients when otherwise undetectable by conventional neuroimaging. As these changes can be detected before patients show symptoms, these patients could be targeted with medication earlier to prevent further deterioration in brain function. These findings are also widely applicable to other forms of neurovascular disease, where early intervention could be of marked therapeutic benefit.
"The problem is that neurological alterations related to hypertension are usually diagnosed only when the cognitive deficit becomes evident, or when traditional magnetic resonance shows clear signs of brain damage. In both cases, it is often too late to stop the pathological process" said Giuseppe Lembo, the coordinator of this study.
"We have been able to see that, in the hypertensive subjects, there was a deterioration of white matter fibers connecting brain areas typically involved in attention, emotions and memory, said Lorenzo Carnevale, IT engineer and first author of the study. "An important aspect to consider is that all the patients studied did not show clinical signs of dementia and, in conventional neuroimaging, they showed no signs of cerebral damage. Of course, further studies will be necessary, but we think that the use of tractography will lead to the early identification of people at risk of dementia, allowing timely therapeutic interventions."
https://www.sciencedaily.com/releases/2018/06/180613101925.htm