Posts tagged science
Articles and news from the latest research reports.
Preparing for adulthood: thousands upon thousands of new cells are born in the hippocampus during puberty, and most survive with effortful learning
The dentate gyrus of the hippocampal formation generates new granule neurons throughout life. The number of neurons produced each day is inversely related to age, with thousands more produced during puberty than during adulthood, and many fewer produced during senescence. In adulthood, approximately half of these cells undergo apoptosis shortly after they are generated. Most of these cells can be rescued from death by effortful and successful learning experiences (Gould et al., 1999; Waddell and Shors, 2008; Curlik and Shors, 2011). Once rescued, the newly-generated cells differentiate into neurons, and remain in the hippocampus for at least several months (Leuner et al., 2004). Here, we report that many new hippocampal cells also undergo cell death during puberty. Because the juvenile brain is more plastic than during adulthood, and because many experiences are new, we hypothesized that a great number of cells would be rescued by learning during puberty. Indeed, adolescent rats that successfully acquired the trace eyeblink response retained thousands more cells than animals that were not trained, and those that failed to learn. Because the hippocampus generates thousands more cells during puberty than during adulthood, these results support the idea that the adolescent brain is especially responsive to learning. This enhanced response can have significant consequences for the functional integrity of the hippocampus. Such a massive increase in cell proliferation is likely an adaptive response as the young animal must emerge from the care of its mother to face the dangers, challenges, and opportunities of adulthood.
Diet Can Predict Cognitive Decline
The importance of long-chain polyunsaturated fatty acids (PUFAs) to brain health has been demonstrated in multiple studies. To assess whether lower dietary intake of alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexanoic acid (DHA) were risk factors for cognitive decline, Tammy Scott, PhD, a scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging (USDA HNRCA) at Tufts University recently conducted a longitudinal, observational study using the Boston Puerto Rican Health Study cohort. Alice Lichtenstein, DSc, also from the USDA HNRCA at Tufts University, and Katherine Tucker, PhD, the cohort director from the University of Massachusetts-Lowell, were co-authors of the study, which has been published as an abstract.
“The participants were put through an intensive series of cognitive tests such as memory tests using a list of words, an attention test to repeat lists of numbers forward and backward, and a test of organization and planning involving copying complex figures,” said Dr. Scott. To determine the participants’ intake of PUFAs they were given a questionnaire. The results were determined after comparing baseline test numbers with a 2 year follow up.
The researchers found that the intake of omega-3 PUFAs in the study sample of 895 participants was low. The 2010 U.S. Dietary Guidelines recommended an intake of 8 or more ounces of seafood per week (less for young children) to ensure an adequate intake of the very long chain omega-3 fatty acids (EPA and DHA). This translates to about 1,750 mg of EPA and DHA per week, which averages to 250 mg per day. Scott’s group reported that only 27% of the participants in their study met or exceeded that recommendation. The major source of EPA and DHA in their diets appeared to be from canned tuna. Based on the scientists’ findings, being in the lowest four quintiles of EPA and DHA intake was predictive of cognitive decline over 2 years.
What is the takeaway from this research? There is growing evidence that very long chain omega-3 fatty acids are beneficial for maintaining cognitive health, and many Americans do not have an adequate intake of these nutrients. “While more research is needed to determine whether intake of fatty fish such as salmon, tuna and trout can help prevent against cognitive decline, our preliminary data support previous research showing that intake of these types of fish have health benefits,” Scott said.
(Image: Fotolia)
Zinc Supplementation Shows Promise in Reducing Cell Stress After Blasts
Each year, approximately 2 million traumatic brain injuries (TBIs) occur in the USA, according to the Centers for Disease Control and Prevention. That number includes troops wounded in Iraq and Afghanistan, for whom TBI is considered an invisible wound of war, one that has few successful treatments. “We have nothing beyond ibuprofen for most TBIs,” said Dr. Angus Scrimgeour, who has been investigating the effects of low zinc diets on cell stress following a blast injury. “The adult brain does not self-repair from this kind of trauma.”
Scrimgeour works for the US Army Research Institute of Environmental Medicine and recently looked at the effects of 5-weeks of low and adequate zinc diets on a specific protein in muscle cells called MMP. The study recreated blast injuries in 32 rats similar to what soldiers experience from IEDs, including loss of consciousness. An equal number of rats served as a control group. Results suggest that zinc supplementation reduces blast-induced cell stress. He presented the results of his research at the American Society for Nutrition’s Scientific Sessions & Annual Meeting at EB on Sunday, April 27.
“We know that soldiers’ brain tissue cannot repair on low zinc diets,” said Scrimgeour. “And they are losing zinc through diarrhea and sweating.” The question moving forward is whether prevention through diet supplementation or post-blast treatment works best to repair behavioral deficits associated with mild TBI.
Scrimgeour added that further research is planned to investigate nutrient combinations for treating mild TBI, including omega-3, vitamin D, glutamine and/or zinc. Although the Army is conducting this research, the results can be applied outside of the military, according to Scrimgeour. “As the blast impact experienced by Soldiers are similar to those experienced during head injuries received in a car accident or during an NFL concussion, these findings could translate from the Soldier to the civilian population.” Scrimgeour cautioned, however, that what works in animals doesn’t always work in soldiers, which is why more research is needed.
(Source: newswise.com)
Fight Memory Loss with a Smile (or Chuckle)
Too much stress can take its toll on the body, mood, and mind. As we age it can contribute to a number of health problems, including high blood pressure, diabetes, and heart disease. Recent research has shown that the stress hormone cortisol damages certain neurons in the brain and can negatively affect memory and learning ability in the elderly. Researchers at Loma Linda University have delved deeper into cortisol’s relationship to memory and whether humor and laughter—a well-known stress reliever—can help lessen the damage that cortisol can cause. Their findings were presented on Sunday, April 27, at the Experimental Biology meeting.
Gurinder Singh Bains et al. showed a 20-minute laugh-inducing funny video to a group of healthy elderly individuals and a group of elderly people with diabetes. The groups where then asked to complete a memory assessment that measured their learning, recall, and sight recognition. Their performance was compared to a control group of elderly people who also completed the memory assessment, but were not shown a funny video. Cortisol concentrations for both groups were also recorded at the beginning and end of the experiment.
The research team found a significant decrease in cortisol concentrations among both groups who watched the video. Video-watchers also showed greater improvement in all areas of the memory assessment when compared to controls, with the diabetic group seeing the most dramatic benefit in cortisol level changes and the healthy elderly seeing the most significant changes in memory test scores.
From the authors: “Our research findings offer potential clinical and rehabilitative benefits that can be applied to wellness programs for the elderly,” Dr. Bains said. “The cognitive components—learning ability and delayed recall—become more challenging as we age and are essential to older adults for an improved quality of life: mind, body, and spirit. Although older adults have age-related memory deficits, complimentary, enjoyable, and beneficial humor therapies need to be implemented for these individuals.”
Study co-author and long-time psychoneuroimmunology humor researcher, Dr. Lee Berk, added, “It’s simple, the less stress you have the better your memory. Humor reduces detrimental stress hormones like cortisol that decrease memory hippocampal neurons, lowers your blood pressure, and increases blood flow and your mood state. The act of laughter—or simply enjoying some humor—increases the release of endorphins and dopamine in the brain, which provides a sense of pleasure and reward. These positive and beneficial neurochemical changes, in turn, make the immune system function better. There are even changes in brain wave activity towards what’s called the “gamma wave band frequency”, which also amp up memory and recall. So, indeed, laughter is turning out to be not only a good medicine, but also a memory enhancer adding to our quality of life.”
Laughter May Work Like Meditation in the Brain
Laughter triggers brain waves similar to those associated with meditation, according to a small new study.
It also found that other forms of stimulation produce different types of brain waves.
The study included 31 people whose brain waves were monitored while they watched humorous, spiritual or distressing video clips. While watching the humorous videos, the volunteers’ brains had high levels of gamma waves, which are the same ones produced during meditation, researchers found.
During the spiritual videos, the participants’ brains showed higher levels of alpha brain waves, similar to when a person is at rest. The distressing videos caused flat brain wave bands, similar to when a person feels detached, nonresponsive or doesn’t want to be in a certain situation.
Researchers were led by Lee Berk, an associate professor in the School of Allied Health Professions, and an associate research professor of pathology and human anatomy in the School of Medicine, at Loma Linda University, in California.
The study was scheduled to be presented Sunday at the Experimental Biology meeting held in San Diego. The data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
“What we have found in our study is that humor associated with mirthful laughter sustains high-amplitude gamma-band oscillations. Gamma is the only frequency found in every part of the brain,” Berk said in a university news release.
“What this means is that humor actually engages the entire brain — it is a whole brain experience with the gamma wave band frequency and humor, similar to meditation, holds it there; we call this being ‘in the zone,’” Berk explained.
He said that with laughter, “it’s as if the brain gets a workout.” This effect is important because it “allows for the subjective feeling states of being able to think more clearly and have more integrative thoughts,” Berk said. “This is of great value to individuals who need or want to revisit, reorganize or rearrange various aspects of their lives or experiences, to make them feel whole or more focused.”
Human consciousness is simply a state of matter, like a solid or liquid – but quantum
Thanks to the work of a small group neuroscientists and theoretical physicists over the last few years, we may finally have found a way of analyzing the mysterious, metaphysical realm of consciousness in a scientific manner. The latest breakthrough in this new field, published by Max Tegmark of MIT, postulates that consciousness is actually a state of matter. “Just as there are many types of liquids, there are many types of consciousness,” he says. With this new model, Tegmark says that consciousness can be described in terms of quantum mechanics and information theory, allowing us to scientifically tackle murky topics such as self awareness, and why we perceive the world in classical three-dimensional terms, rather than the infinite number of objective realities offered up by the many-worlds interpretation of quantum mechanics.
The Influence of Spatiotemporal Structure of Noisy Stimuli in Decision Making
Decision making is a process of utmost importance in our daily lives, the study of which has been receiving notable attention for decades. Nevertheless, the neural mechanisms underlying decision making are still not fully understood. Computational modeling has revealed itself as a valuable asset to address some of the fundamental questions. Biophysically plausible models, in particular, are useful in bridging the different levels of description that experimental studies provide, from the neural spiking activity recorded at the cellular level to the performance reported at the behavioral level. In this article, we have reviewed some of the recent progress made in the understanding of the neural mechanisms that underlie decision making. We have performed a critical evaluation of the available results and address, from a computational perspective, aspects of both experimentation and modeling that so far have eluded comprehension. To guide the discussion, we have selected a central theme which revolves around the following question: how does the spatiotemporal structure of sensory stimuli affect the perceptual decision-making process? This question is a timely one as several issues that still remain unresolved stem from this central theme. These include: (i) the role of spatiotemporal input fluctuations in perceptual decision making, (ii) how to extend the current results and models derived from two-alternative choice studies to scenarios with multiple competing evidences, and (iii) to establish whether different types of spatiotemporal input fluctuations affect decision-making outcomes in distinctive ways. And although we have restricted our discussion mostly to visual decisions, our main conclusions are arguably generalizable; hence, their possible extension to other sensory modalities is one of the points in our discussion.
Half of homeless men had traumatic brain injury
Study finds almost half of homeless men had traumatic brain injury in their lifetime, vast majority before they lost their homes
Almost half of all homeless men who took part in a study by St. Michael’s Hospital had suffered at least one traumatic brain injury in their life and 87 per cent of those injuries occurred before the men lost their homes.
While assaults were a major cause of those traumatic brain injuries, or TBIs, (60 per cent) many were caused by potentially non-violent mechanisms such as sports and recreation (44 per cent) and motor vehicle collisions and falls (42 per cent).
The study, led by Dr. Jane Topolovec-Vranic, a clinical researcher in the hospital’s Neuroscience Research Program, was published in the journal CMAJ Open.
Dr. Topolovec-Vranic said it’s important for health care providers and others who work with homeless people to be aware of any history of TBI because of the links between such injuries and mental health issues, substance abuse, seizures and general poorer physical health.
The fact that so many homeless men suffered a TBI before losing their home suggests such injuries could be a risk factor for becoming homeless, she said. That makes it even more important to monitor young people who suffer TBIs such as concussions for health and behavioural changes, she said.
Dr. Topolovec-Vranic looked at data on 111 homeless men aged 27 to 81 years old who were recruited from a downtown Toronto men’s shelter. She found that 45 per cent of these men had experienced a traumatic brain injury, and of these, 70 per cent were injured during childhood or teenage years and 87 per cent experienced an injury before becoming homeless.
In men under age 40, falls from drug/alcohol blackouts were the most common cause of traumatic brain injury while assault was the most common in men over 40 years old.
Recognition that a TBI sustained in childhood or early teenage years could predispose someone to homelessness may challenge some assumptions that homelessness is a conscious choice made by these individuals, or just the result of their addictions or mental illness, said Dr. Topolovec-Vranic.
This study received funding from the Canadian Institutes of Health Research and the Ontario Neurotrauma Foundation.
Separately, a recent study by Dr. Stephen Hwang of the hospital’s Centre for Research on Inner City Health, found the number of people who are homeless or vulnerably housed and who have also suffered a TBI may be as high as 61 per cent—seven times higher than the general population.
Dr. Hwang’s study, published in the Journal of Head Trauma Rehabilitation, is one of the largest studies to date investigating TBI in homeless populations. The findings come from the Health and Housing in Transition Study, which tracks the health and housing status of homeless and vulnerably housed people in Toronto, Vancouver and Ottawa.
(Source: stmichaelshospital.com)
ADHD Drug May Help Preserve Our Self-Control Resources
Methylphenidate, also known as Ritalin, may prevent the depletion of self-control, according to research published in Psychological Science, a journal of the Association for Psychological Science.
Self-control can be difficult — sticking with a diet or trying to focus attention on a boring textbook are hard things to do. Considerable research suggests one potential explanation for this difficulty: Exerting self-control for a long period seems to “deplete” our ability to exert self-control effectively on subsequent tasks.
“It is as if self-control is a limited resource that ‘runs out’ if it is used too much,” says lead researcher Chandra Sripada of the University of Michigan. “If we could figure out the brain mechanisms that cause regulatory depletion, then maybe we could find a way to prevent it.”
Previous research has implicated the neurotransmitters dopamine and norepinephrine in regulatory processing. Sripada and University of Michigan collaborators Daniel Kessler and John Jonides decided to see whether manipulating levels of these transmitters might affect regulatory depletion.
The researchers tested 108 adult participants, all of whom took a drug capsule 60 minutes prior to testing. Half of the participants received a capsule that contained methylphenidate, a medication used to treat ADHD that increases brain dopamine and norepinephrine. The other half received a placebo capsule. The study was double-blind, so neither the participants nor the researchers knew at the time of testing who had received which capsule.
The participants then completed a computer-based task in which they were required to press a button when a word containing the letter e appeared on screen. Some were given modified instructions that asked them to refrain from pressing the button if the letter e was next to or one extra letter away from another vowel — this version of the task was designed to tax participants’ self-control.
All of the participants then completed a second computer task aimed at testing their ability to process competing information and exert regulatory control in order to make a correct response.
In line with the researchers’ hypotheses, participants who received the placebo and performed the taxing version of the first task showed greater variability in how quickly they responded in the second task, compared to those whose self-control hadn’t been depleted in the first task.
But for those participants who took the methylphenidate capsule, the first task didn’t have an effect on later performance — the methylphenidate seemed to counteract the self-regulatory depletion incurred by the harder version of the first task.
“These results indicate that depletion of self-control due to prior effort can be fully blocked pharmacologically,” says Sripada. “The task we give people to deplete their self-control is pretty cognitively demanding, so we were surprised at how effective methylphenidate was in blocking depletion of self-control.”
Sripada and colleagues suggest that methylphenidate may help to boost performance of the specific circuits in the brain’s prefrontal cortex that are normally compromised after sustained exertion of self-control.
This doesn’t mean, however, that those of us looking to boost our self-control should go out and get some Ritalin:
“Methylphenidate is a powerful psychotropic medicine that should only be taken with a prescription,” says Sripada. “We want to use this research to better understand the brain mechanisms that lead to depletion of self-control, and what interventions — pharmacological or behavioral — might prevent this.”
New study links inflammation in those with PTSD to changes in microRNA
With a new generation of military veterans returning home from Iraq and Afghanistan, post-traumatic stress disorder (PTSD) has become a prominent concern in American medical institutions and the culture at-large. Estimates indicate that as many as 35 percent of personnel deployed to Iraq and Afghanistan suffer from PTSD. New research from the University of South Carolina School of Medicine is shedding light on how PTSD is linked to other diseases in fundamental and surprising ways.
The rise in PTSD has implications beyond the impact of the psychiatric disorder and its immediate consequences, which include elevated suicide risk and inability to lead a normal life, that result in approximately $3 billion in lost productivity every year. Over time, these PTSD patients will continue to experience increased risks of a myriad of medical conditions like cardiovascular disease, diabetes, gastrointestinal disease, fibromyalgia, musculoskeletal disorders and others, all of which share chronic inflammation as a common underlying cause.
The mechanisms that trigger PTSD, and that cause PTSD patients to suffer from higher rates of chronic-inflammation-related medical conditions remain unknown. Additionally, PTSD is incurable, and though there are available treatments, they are often not completely effective. In an effort to get to the root of PTSD, and begin to understand the links between PTSD and the secondary diseases that often come with it, a team at the University of South Carolina School of Medicine is investigating PTSD through the lens of inflammation. They have recently published findings of a new study, “Dysregulation in microRNA Expression is Associated with Alterations in Immune Functions in Combat Veterans with Post-traumatic Stress Disorder,” in the journal PLOS ONE.
In this study, led by Drs. Prakash Nagarkatti and Mitzi Nagarkatti, the authors investigated microRNA profiles and tried to establish a link between the microRNA and inflammation in combat veterans of the Persian Gulf, Iraq and Afghanistan wars who are PTSD patients at the Dorn VA Medical Center. MicroRNA are small, noncoding RNA that can switch human genes on and off, effectively controlling gene expression. Some specific types of microRNA are known to regulate genes involved in inflammation, making them a kind of marker that can indicate when inflammation is present.
The microRNA role in PTSD has not been investigated previous to this study, which found that the PTSD patients had significant alterations in microRNA expression. The study analyzed 1163 microRNA and found that the expression of microRNA that regulate genes involved in inflammation were altered in PTSD patients. The alterations were found to be linked to heightened inflammation in these patients.
Dr. Mitzi Nagarkatti sums up the significance of this study as follows: “We are very excited about these results. Thus far, no one had looked at the role of microRNA in the blood of PTSD patients. Thus, our finding that the alterations in these small molecules are connected to higher inflammation seen in these patients is very interesting and helps establish the connection between war trauma and microRNA changes.”
In addition to the alterations in microRNA expression, the study also found that PTSD patients had higher levels of inflammation caused by certain types of immune cells called T cells. These T cells produced higher levels of inflammatory mediators called cytokines, specifically interferon-gamma and interleukin-17. This finding was especially interesting because one of the inflammation-associated microRNAs, miR-125a, which specifically targets increased production of interferon-gamma, was found to have decreased expression in the PTSD patients studied. Overall, these results suggested that trauma may cause alterations in the expression of microRNA which promote inflammation in PTSD patients.
Commenting on this, Dr. Prakash Nagarkatti said, “These studies form the foundation to further analyze the role of microRNA in PTSD. Trauma experienced during war may trigger changes in microRNA which may in turn cause various clinical disorders seen in PTSD patients. Our long-term goal is to identify whether PTSD patients express a unique signature profile of microRNA which can be used towards early detection, prevention and treatment of PTSD.”
(Source: eurekalert.org)