Neuroscience
Month
There’s no question that our ability to remember informs our sense of self. Now research published in Clinical Psychological Science, a journal of the Association for Psychological Science, provides new evidence that the relationship may also work the other way around: Invoking our sense of self can influence what we are able to remember.
Research has shown that self-imagination – imagining something from a personal perspective – can be an effective strategy for helping us to recognize something we’ve seen before or retrieve specific information on cue. And these beneficial effects have been demonstrated for both healthy adults and for individuals who suffer memory impairments as a result of brain injury.
These findings suggest that self-imagination is a promising strategy for memory rehabilitation. But no study has investigated the effect of self-imagination on what is perhaps the most difficult, and most relevant, type of memory: free recall.
Targeted light transmission to genetically altered brain cells stops seizures cold.
Strobe lights can trigger epileptic seizures. Now imagine a light that stops a seizure a split second after it starts.
By applying pulses of light to genetically altered nerve cells deep in rat brains, researchers at Stanford and Pierre and Marie Curie University in France have done just that. Their results, which showed for the first time how a part of the brain called the thalamus is involved with epileptic seizures, were published in Nature Neuroscience.
The study could point toward new targets for epilepsy treatment, says Ed Boyden, associate professor and leader of the Synthetic Biology Group at MIT. Boyden was not involved in the work. Some ideas “might emerge immediately from knowing new targets to insert deep brain stimulation electrodes,” a type of device already used to help people with epilepsy, Boyden says.
The latest research looked at a kind of seizure that sometimes follows damage to the cerebral cortex, the outer part of the brain, from strokes or head injuries. Previous reports had hinted that the cortex might also communicate during a seizure with the thalamus, the brain’s message relay center.
In the current study, experiments with rats confirmed that the thalamus propagates seizure activity originating in the cortex. To see if the thalamus could be a target for treating seizures, Jeanne Paz, the paper’s lead author, and her colleagues turned to optogenetics, a technology that lets researchers use light to turn brain cells on and off.
For the “genetics” part, they used a virus to insert the DNA code for a light-sensitive protein into thalamus cells of rats. When exposed to light, the protein interferes with these cells’ ability to communicate.
The researchers then developed a light source that would turn on only when a rat had a seizure. To detect seizures, they implanted electrodes into the rats’ brains. When these electrodes registered a seizure starting, light from a laser was aimed directly at the genetically altered thalamus cells. The result, the researchers found, was that flipping on the light immediately stopped the seizure activity, proving that the thalamus is needed to keep seizures going.
“We’re excited that just a brief light exposure was enough to stop the seizure,” says John Huguenard, Stanford professor of neurology and neurological sciences and an author of the study.
However, Huguenard says, an optogenetics-based brain implant to control seizures is a long way off because of the unknown risks of altering a person’s DNA with a virus. “I would want to be cautious,” he says.
UC Irvine researchers have created a new stem cell-derived cell type with unique promise for treating neurodegenerative diseases such as Alzheimer’s.
Dr. Edwin Monuki of UCI’s Sue & Bill Gross Stem Cell Research Center, developmental & cell biology graduate student Momoko Watanabe and colleagues developed these cells — called choroid plexus epithelial cells — from existing mouse and human embryonic stem cell lines.
CPECs are critical for proper functioning of the choroid plexus, the tissue in the brain that produces cerebrospinal fluid. Among their various roles, CPECs make CSF and remove metabolic waste and foreign substances from the fluid and brain.
In neurodegenerative diseases, the choroid plexus and CPECs age prematurely, resulting in reduced CSF formation and decreased ability to flush out such debris as the plaque-forming proteins that are a hallmark of Alzheimer’s. Transplant studies have provided proof of concept for CPEC-based therapies. However, such therapies have been hindered by the inability to expand or generate CPECs in culture.
“Our method is promising, because for the first time we can use stem cells to create large amounts of these epithelial cells, which could be utilized in different ways to treat neurodegenerative diseases,” said Monuki, an associate professor of pathology & laboratory medicine and developmental & cell biology at UCI.
The study appears in The Journal of Neuroscience
To create the new cells, Monuki and his colleagues coaxed embryonic stem cells to differentiate into immature neural stem cells. They then developed the immature cells into CPECs capable of being delivered to a patient’s choroid plexus.
These cells could be part of neurodegenerative disease treatments in at least three ways, Monuki said. First, they’re able to increase the production of CSF to help flush out plaque-causing proteins from brain tissue and limit disease progression. Second, CPEC “superpumps” could be designed to transport high levels of therapeutic compounds to the CSF, brain and spinal cord. Third, these cells can be used to screen and optimize drugs that improve choroid plexus function.
Monuki said the next steps are to develop an effective drug screening system and to conduct proof-of-concept studies to see how these CPECs affect the brain in mouse models of Huntington’s, Alzheimer’s and pediatric diseases.
When it comes to Alzheimer’s disease, scientists usually — and understandably — look to the brain as their first center of attention. Now researchers at Tel Aviv University say that early clues regarding the progression of the disease can be found in the brain’s metabolism.
In very early stages of the disease, before any symptoms appear, metabolic processes are already beginning to change in the brain, says PhD candidate Shiri Stempler of TAU’s Sackler Faculty of Medicine. Working with Profs. Eytan Ruppin and Lior Wolf of TAU’s Blavatnik School of Computer Science, Stempler has developed predictor models that use metabolic information to pinpoint the progression of Alzheimer’s. These models were 90 percent accurate in predicting the stage of the disease.
Published in the journal Neurobiology of Aging, the research is the first step towards identifying biomarkers that may ensure better detection and analysis of the disease at an early stage, all with a simple blood test. It could also lead to novel therapies. “We hope that by studying metabolism, and the alterations to metabolism that occur in the very early stages of the disease, we can find new therapeutic strategies,” adds Stempler.
Every week in his clinic at the University of Michigan, neurologist Joseph Corey, M.D., Ph.D., treats patients whose nerves are dying or shrinking due to disease or injury.
He sees the pain, the loss of ability and the other effects that nerve-destroying conditions cause – and wishes he could give patients more effective treatments than what’s available, or regenerate their nerves. Then he heads to his research lab at the VA Ann Arbor Healthcare System, where his team is working toward that exact goal.
In new research published in several recent papers (Nature Methods, Biomacromolecules, Materials Science and Engineering) Corey and his colleagues from the U-M Medical School, VAAAHS and the University of California, San Francisco report success in developing polymer nanofiber technologies for understanding how nerves form, why they don’t reconnect after injury, and what can be done to prevent or slow damage.
Using polymer nanofibers thinner than human hairs as scaffolds, researchers coaxed a particular type of brain cell to wrap around fibers that mimic the shape and size of nerves found in the body.
They’ve even managed to encourage the process of myelination – the formation of a protective coating that guards larger nerve fibers from damage. They began to see multiple concentric layers of the protective substance called myelin start to form, just as they do in the body.
Humans share over 90% of their DNA with their primate cousins. The expression or activity patterns of genes differ across species in ways that help explain each species’ distinct biology and behavior.
DNA factors that contribute to the differences were described on Nov. 6 at the American Society of Human Genetics 2012 meeting in a presentation by Yoav Gilad, Ph.D., associate professor of human genetics at the University of Chicago.
Dr. Gilad reported that up to 40% of the differences in the expression or activity patterns of genes between humans, chimpanzees and rhesus monkeys can be explained by regulatory mechanisms that determine whether and how a gene’s recipe for a protein is transcribed to the RNA molecule that carries the recipe instructions to the sites in cells where proteins are manufactured.
In addition to improving scientific understanding of the uniqueness of humans, studies such as the investigation conducted by Dr. Gilad and colleagues could have relevance to human health and disease.
"Through inter-species’ comparisons at the DNA sequence and expression levels, we hope to identify the genetic basis of human specific traits and in particular the genetic variations underlying the higher susceptibility to certain diseases such as malaria and cancer in humans than in non-human primates," said Dr. Gilad.
Dr. Gilad and his colleagues studied gene expression in lymphoblastoid cell lines, laboratory cultures of immortalized white blood cells, from eight humans, eight chimpanzees and eight rhesus monkeys.
They found that the distinct gene expression patterns of the three species can be explained by corresponding changes in genetic and epigenetic regulatory mechanisms that determine when and how a gene’s DNA code is transcribed to a messenger RNA (mRNA) molecule.
Dr. Gilad also determined that the epigenetics process known as histone modification also differs in the three species. The presence of histone marks during gene transcription indicates that the process is being prevented or modified.
"These data allowed us to identify both conserved and species-specific enhancer and repressor regulatory elements, as well as characterize similarities and differences across species in transcription factor binding to these regulatory elements," Dr. Gilad said.
Among the similarities among the three species were the promoter regions of DNA that initiated transcription of a particular gene.
In all three species, Dr. Gilad’s lab found that transcription factor binding and histone modifications were identical in over 67% of regulatory elements in DNA segments that are regarded as promoter regions.
The researchers presentation is titled, “Genome-wide comparison of genetic and epigenetic regulatory mechanisms in primates.”
Scientists at the Universities of Liverpool and Glasgow have uncovered a possible new method of enhancing nerve repair in the treatment of spinal cord injuries.
It is known that scar tissue, which forms following spinal cord injury, creates an impenetrable barrier to nerve regeneration, leading to the irreversible paralysis associated with spinal injuries. Scientists at Liverpool and Glasgow have discovered that long-chain sugars, called heparan sulfates, play a significant role in the process of scar formation in cell models in the laboratory.
Research findings have the potential to contribute to new strategies for manipulating the scarring process induced in spinal cord injury and improving the effectiveness of cell transplantation therapies in patients with this type of injury.
Scarring occurs due to the activation, change in shape, and stiffness of cells, called astrocytes, which are the major nerve support cells in the spinal cord. One possible way to repair nerve damage is transplantation of support cells from peripheral nerves, called Schwann cells. The team, however, found that these cells secrete heparan sulfate sugars, which promote scarring reactions and could reduce the effectiveness of nerve repair.
Scientists showed that these sugars can over-activate protein growth factors that promote astrocyte scarring. Significantly, however, they found this over-activation could be inhibited by chemically modified heparins made in the laboratory. These compounds could prevent the scarring reaction of astrocyte cells, opening up new opportunities for treatment of damaged nerve cells.
Professor Jerry Turnbull, from the University of Liverpool’s Institute of Integrative Biology, said: “Spinal injury is a devastating condition and can result in paralysis for life. The sugars we are investigating are produced by nearly every cell in the body, and are similar to the blood thinning drug heparin.
"We found that some sugar types promote scarring reaction, but remarkably other types, which can be chemically produced in the laboratory by modifying heparin, can prevent this in our cell models.
"Studies in animal cells are now needed, but the exciting thing about this work is that it could, in the future, provide a way of developing treatments for improving nerve repair in patients, using the body’s own Schwann cells, supplemented with specific sugars."
Professor Sue Barnett, from the University of Glasgow’s Institute of Infection, Immunity and Inflammation, said: “We had already shown that Schwann cells, identified as having the potential to promote nerve regrowth, induced scarring in spinal cord injury. Now that we know that they secrete these complex sugars, which lead to scarring, we have the opportunity to intervene in this process, and promote central nervous system repair.”
New findings led by Dr. Michael Lombardo, Prof. Simon Baron-Cohen and colleagues at the University of Cambridge indicate that testosterone levels early in fetal development influence later sensitivity of brain regions related to reward processing and affect an individual’s susceptibility to engage in behavior, that in extremes, are related to several neuropsychiatric conditions that asymmetrically affect one sex more than the other.
Although present at low levels in females, testosterone is one of the primary sex hormones that exerts substantial influence over the emergence of differences between males and females. In adults and adolescents, heightened testosterone has been shown to reduce fear, lower sensitivity to punishment, increase risk-tasking, and enhance attention to threat. These effects interact substantially with context to affect social behavior.
This knowledge about the effects of testosterone in adolescence and adulthood suggests that it is related to influencing the balance between approach and avoidance behavior. These same behaviors are heightened in the teenage years and also emerge in extremes in many neuropsychiatric conditions, including conduct disorder, depression, substance abuse, autism, and psychopathy.
Scientists have long known that sex differences influence many aspects of psychiatric disorders, including age of disease onset, prevalence, and susceptibility. For example, according to the World Health Organization, depression is twice as common in women than men, whereas alcohol dependence shows the reverse pattern. In addition to many other factors, sex hormone levels are likely to be important factors contributing to sex differences in psychopathology.
However, research to date has mainly focused on sex hormone levels during adolescence and adulthood, when hormone levels are heightened and built upon substantial prior developmental experience. Sex hormone levels are also heightened during critical periods of fetal brain development, but the impact of such prenatal surges in sex hormone levels on subsequent adult brain and behavioral development has received relatively little attention.
"This study is the first to directly examine whether testosterone in fetal development predicts tendencies later in life to engage in approach-related behavior (e.g., fun-seeking, impulsivity, reward responsivity) and also how it may influence later brain development that is relevant to such behaviors," said first author Lombardo.
In this study, they tested a unique cohort of boys, 8-11 years of age, whose fetal testosterone had been previously measured from amniotic fluid at 13-20 weeks gestation. The boys were scanned with functional magnetic resonance imaging technology to assess changes in brain activity while viewing pictures of negative (fear), positive (happy), neutral, or scrambled faces.
They found that increased fetal testosterone predicted more sensitivity in the brain’s reward system to positively, compared to negatively, valenced facial cues. This means that reward-related brain regions of boys with higher fetal testosterone levels respond more to positive facial emotion compared to negative facial emotion than boys who with smaller levels of fetal testosterone.
In addition, increased fetal testosterone levels predicted increased behavioral approach tendencies later in life via its influence on the brain’s reward system. Lombardo explained, “This work highlights how testosterone in fetal development acts as a programming mechanism for shaping sensitivity of the brain’s reward system later in life and for predicting later tendency to engage in approach-related behaviors. These insights may be especially relevant to a number of neuropsychiatric conditions with skewed sex ratios and which affect approach-related behavior and the brain’s reward system.”
Dr. John Krystal, Editor of Biological Psychiatry, commented, “These remarkable data provide new evidence that hormonal exposures early in life can have lasting impact on brain function and behavior.”
Low levels of vitamin D may be associated with longevity, according to a study involving middle-aged children of people in their 90s published in CMAJ (Canadian Medical Association Journal).
"We found that familial longevity was associated with lower levels of vitamin D and a lower frequency of allelic variation in the CYP2R1 gene, which was associated with higher levels of vitamin D," writes Dr. Diana van Heemst, Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands, with coauthors.
Previous studies have shown that low levels of vitamin D are associated with increased rates of death, heart disease, diabetes, cancer, allergies, mental illness and other afflictions. However, it is not known whether low levels are the cause of these diseases or if they are a consequence.
To determine whether there was an association between vitamin D levels and longevity, Dutch researchers looked at data from 380 white families with at least 2 siblings over age 90 (89 years or older for men and 91 year or older for women) in the Leiden Longevity Study. The study involved the siblings, their offspring and their offsprings’ partners for a total of 1038 offspring and 461 controls. The children of the nonagenarians were included because it is difficult to include controls for the older age group. The partners were included because they were of a similar age and shared similar environmental factors that might influence vitamin D levels.
The researchers measured levels of 25(OH) vitamin D and categorized levels by month as they varied according to season. Tanning bed use, which can affect vitamin D levels, was categorized as never, 1 times per year and 6 times per year. The researchers controlled for age, sex, BMI (body mass index), time of year, vitamin supplementation and kidney function, all factors that can influence vitamin D levels. They also looked at the influence of genetic variation in 3 genes associated with vitamin D levels.
"We found that the offspring of nonagenarians who had at least 1 nonagenarian sibling had lower levels of vitamin D than controls, independent of possible confounding factors and SNPs [single nucleotide polymorphisms] associated with vitamin D levels," write the authors. "We also found that the offspring had a lower frequency of common genetic variants in the CYP2R1 gene; a common genetic variant of this gene predisposes people to high vitamin D levels.
These findings support an association between low vitamin D levels and familial longevity.” They postulate that offspring of nonagenarians might have more of a protein that is hypothesized to be an “aging suppressor” protein. More research is needed to understand the link between lower vitamin D levels, genetic variants and familial longevity.
Over the last 15 years, researchers have found a significant association between vascular diseases such as hypertension, atherosclerosis, diabetes type 2, hyperlipidemia, and heart disease and an increased risk of Alzheimer’s disease. In a special issue of the Journal of Alzheimer’s Disease, leading experts provide a comprehensive overview of the pathological, biochemical, and physiological processes that contribute to Alzheimer’s disease risk and ways that may delay or reverse these age-related abnormalities.
“Vascular risk factors to Alzheimer’s disease offer the possibility of markedly reducing incident dementia by early identification and appropriate medical management of these likely precursors of cognitive deterioration and dementia,” says Guest Editor Jack C. de la Torre, MD, PhD, of the University of Texas, Austin. “Improved understanding coupled with preventive strategies could be a monumental step forward in reducing worldwide prevalence of Alzheimer’s disease, which is doubling every 20 years.”
The issue explores how vascular disease can affect cerebral blood flow and impair signaling, contributing to Alzheimer’s disease (AD). The diagnostics of cardiovascular risk factors in AD are addressed, as are potential therapeutic approaches.
Paradoxically, the presence of vascular risk factors in middle age is associated with the development of AD more strongly than late-life vascular disease. In fact, some research suggests that vascular symptoms later in life may have a protective effect against the development of the disease. The physiopathological mechanisms that may underlie this phenomenon are discussed.
To date, trials that target major cardiovascular risk factors in the prevention of AD remain inconclusive but have become an important focus of international research as described by contributors of this special volume in their overviews. The multifactorial nature of AD and the need to identify the proper time window for intervention when designing possible interventions, and methodological issues that will have to be addressed to achieve an optimal design of new randomized controlled trials, are discussed. Promising avenues for treatment, such as the potential of low-level light therapy to increase the rate of oxygen consumption in the brain and enhance cortical metabolic capacity, and the possibility that some antihypertensive drug classes reduce the risk and progression of AD more than others, are discussed.
Dr. de la Torre notes that the presence of vascular risk factors is not an absolute pathway to dementia, and it may be as important to study how or why individuals who are cognitively normal but have vascular risk are able to avoid dementia. “Reducing Alzheimer’s disease prevalence by focusing right now on vascular risk factors to Alzheimer’s disease, even with our limited technology, is not a simple or easy task. But the task must begin somewhere and without delay because time is running out for millions of people whose destiny with dementia may start sooner rather than later,” he concludes.
Dr. James Russell and a research team at the University of Cambridge recently published work on young children’s conception of personal visibility, which furthers the understanding of cognitive development and of our emerging sense of self.
The research involved children three to four years of age. Researchers placed an eye mask on each of the children and asked them if they could be seen when wearing it. They then asked each child if an adult who was wearing a similar mask could be seen. The majority of the children involved in the study believed they were not visible when wearing the mask. Most also believed that the adult wearing the eye mask was also hidden.
Additional tests revealed a unique layer of complexity, demonstrating that although the children thought they were invisible when there eyes were covered, they still believed that their head and body were able to be seen.
The research team concluded by process of elimination that the factor that makes children believe they are visible is eye contact with another person.
“… it would seem that children apply the principle of joint attention to the self and assume that for somebody to be perceived, experience must be shared and mutually known to be shared, as it is when two pairs of eyes meet,” the researchers reported. “Young children’s natural tendency to acquire knowledge intersubjectively, by joint attention, leads them to undergo a developmental period in which they believe the self is something that must be mutually experienced for it to be perceived.”
Evidently, children only believe they exist when making eye contact with another person. The implications point to a simple but necessary way to make children feel present and involved. Cultures worldwide seem to have some version of “peek-a-boo,” as a quick Google image search reveals. Lack of eye contact in children has been linked as an early sign of autism, while the presence of eye contact is associated with empathy. Dr. Russell’s team seems to have discovered a key facet of cognitive development.
The results of Dr. Russell’s study were published in the Journal of Cognition and Development.