Posts tagged memory
Articles and news from the latest research reports.
Regular aerobic exercise boosts memory area of brain in older women
Regular aerobic exercise seems to boost the size of the area of the brain (hippocampus) involved in verbal memory and learning among women whose intellectual capacity has been affected by age, indicates a small study published online in the British Journal of Sports Medicine.
The hippocampus has become a focus of interest in dementia research because it is the area of the brain involved in verbal memory and learning, but it is very sensitive to the effects of ageing and neurological damage.
The researchers tested the impact of different types of exercise on the hippocampal volume of 86 women who said they had mild memory problems, known as mild cognitive impairment - and a common risk factor for dementia.
All the women were aged between 70 and 80 years old and were living independently at home.
Roughly equal numbers of them were assigned to either twice weekly hour long sessions of aerobic training (brisk walking); or resistance training, such as lunges, squats, and weights; or balance and muscle toning exercises, for a period of six months.
The size of their hippocampus was assessed at the start and the end of the six month period by means of an MRI scan, and their verbal memory and learning capacity was assessed before and afterward using a validated test (RAVLT).
Only 29 of the women had before and after MRI scans, but the results showed that the total volume of the hippocampus in the group who had completed the full six months of aerobic training was significantly larger than that of those who had lasted the course doing balance and muscle toning exercises.
No such difference in hippocampal volume was seen in those doing resistance training compared with the balance and muscle toning group.
However, despite an earlier finding in the same sample of women that aerobic exercise improved verbal memory, there was some evidence to suggest that an increase in hippocampal volume was associated with poorer verbal memory.
This suggests that the relationship between brain volume and cognitive performance is complex, and requires further research, say the authors.
But at the very least, aerobic exercise seems to be able to slow the shrinkage of the hippocampus and maintain the volume in a group of women who are at risk of developing dementia, they say.
And they recommend regular aerobic exercise to stave off mild cognitive decline, which is especially important, given the mounting evidence showing that regular exercise is good for cognitive function and overall brain health, and the rising toll of dementia.
Worldwide, one new case of dementia is diagnosed every four seconds, with the number of those afflicted set to rise to more than 115 million by 2050, they point out.
Older People with Faster Decline In Memory and Thinking Skills May Have Lower Risk of Cancer Death
Older people who are starting to have memory and thinking problems, but do not yet have dementia may have a lower risk of dying from cancer than people who have no memory and thinking problems, according to a study published in the April 9, 2014, online issue of Neurology®, the medical journal of the American Academy of Neurology.
“Studies have shown that people with Alzheimer’s disease are less likely to develop cancer, but we don’t know the reason for that link,” said study author Julián Benito-León, MD, PhD, of University Hospital 12 of October in Madrid, Spain. “One possibility is that cancer is underdiagnosed in people with dementia, possibly because they are less likely to mention their symptoms or caregivers and doctors are focused on the problems caused by dementia. The current study helps us discount that theory.”
The study involved 2,627 people age 65 and older in Spain who did not have dementia at the start of the study. They took tests of memory and thinking skills at the start of the study and again three years later, and were followed for an average of almost 13 years. The participants were divided into three groups: those whose scores on the thinking tests were declining the fastest, those whose scores improved on the tests, and those in the middle.
During the study, 1,003 of the participants died, including 339 deaths, or 34 percent, among those with the fastest decline in thinking skills and 664 deaths, or 66 percent, among those in the other two groups. A total of 21 percent of those in the group with the fastest decline died of cancer, according to their death certificates, compared to 29 percent of those in the other two groups.
People in the fastest declining group were still 30 percent less likely to die of cancer when the results were adjusted to control for factors such as smoking, diabetes and heart disease, among others.
“We need to understand better the relationship between a disease that causes abnormal cell death and one that causes abnormal cell growth,” Benito-León said. “With the increasing number of people with both dementia and cancer, understanding this association could help us better understand and treat both diseases.”
Memory Accuracy and Strength Can Be Manipulated During Sleep
The sense of smell might seem intuitive, almost something you take for granted. But researchers from NYU Langone Medical Center have found that memory of specific odors depends on the ability of the brain to learn, process and recall accurately and effectively during slow-wave sleep — a deep sleep characterized by slow brain waves.
The sense of smell is one of the first things to fail in neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, and schizophrenia. Indeed, down the road, if more can be learned from better understanding of how the brain processes odors, researchers believe it could lead to novel therapies that target specific neurons in the brain, perhaps enhancing memory consolidation and memory accuracy.
Reporting in the Journal of Neuroscience online April 9, researchers in the lab of Donald A. Wilson, PhD, a professor in the departments of Child and Adolescent Psychiatry and Neuroscience and Physiology at NYU Langone, and a research scientist at the NYU-affiliated Nathan Kline Institute for Psychiatric Research, showed in experiments with rats that odor memory was strengthened when odors sensed the previous day were replayed during sleep. Memories deepened more when odor reinforcement occurred during sleep than when rats were awake.
When the memory of a specific odor learned when the rats were awake was replayed during slow-wave sleep, they achieved a stronger memory for that odor the next day, compared to rats that received no replay, or only received replay when they were awake.
However, when the research team exposed the rats to replay during sleep of an odor pattern that they had not previously learned, the rats had false memories to many different odors. When the research team pharmacologically prevented neurons from communicating to each other during slow-wave sleep, the accuracy of memory of the odor was also impaired.
The rats were initially trained to recognize odors through conditioning. Using electrodes in the olfactory bulb, a part of the brain responsible for perceiving smells, the researchers stimulated different smell perceptions, according to precise patterns of electrical stimulation. Then, by replaying the patterns electrically, they were able to test the effects of slow-wave sleep manipulation.
Replay of learned electrical odors during slow-wave sleep enhanced the memory for those odors. When the learned smells were replayed while the rats were awake, the strength of the memory decreased. Finally, when a false pattern that the rat never learned was incorporated, the rats could not discriminate the smell accurately from the learned odor.
“Our findings confirm the importance of brain activity during sleep for both memory strength and accuracy,” says Dr. Wilson, the study’s senior author. “What we think is happening is that during slow-wave sleep, neurons in the brain communicate with each other, and in doing so, strengthen their connections, permitting storage of specific information.”
Dr. Wilson says these findings are the first to demonstrate that memory accuracy, not just memory strength, is altered during short-wave sleep. In future research, Dr. Wilson and his team hope to examine how sleep disorders affect memory and perception.
From Learning in Infancy to Planning Ahead in Adulthood: Sleep’s Vital Role for Memory
Babies and young children make giant developmental leaps all of the time. Sometimes, it seems, even overnight they figure out how to recognize certain shapes or what the word “no” means no matter who says it. It turns out that making those leaps could be a nap away: New research finds that infants who nap are better able to apply lessons learned to new skills, while preschoolers are better able to retain learned knowledge after napping.
“Sleep plays a crucial role in learning from early in development,” says Rebecca Gómez of the University of Arizona. She will be presenting her new work, which looks specifically at how sleep enables babies and young children to learn language over time, at the Cognitive Neuroscience Society (CNS) annual meeting in Boston today, as part of a symposium on sleep and memory.
“We want to show that sleep is not just a necessary evil for the organism to stay functional,” says Susanne Diekelmann of the University of Tübingen in Germany who is chairing the symposium. “Sleep is an active state that is essential for the formation of lasting memories.”
A growing body of research shows how memories become reactivated during sleep, and new work is shedding light on exactly when and how memories get stored and reactivated. “Sleep is a highly selective state that preferentially strengthens memories that are relevant for our future behavior,” Diekelmann says. “Sleep can also abstract general rules from single experiences, which helps us to deal more efficiently with similar situations in the future.”
Running, Cardio Activities in Young Adulthood May Preserve Thinking Skills in Middle Age
Young adults who run or participate in other cardio fitness activities may preserve their memory and thinking skills in middle age, according to a new study published in the April 2, 2014, online issue of Neurology®, the medical journal of the American Academy of Neurology. Middle age was defined as ages 43 to 55.
“Many studies show the benefits to the brain of good heart health,” said study author David R. Jacobs, Jr, PhD, with the University of Minnesota in Minneapolis. “This is one more important study that should remind young adults of the brain health benefits of cardio fitness activities such as running, swimming, biking or cardio fitness classes.”
Cardiorespiratory fitness is a measure of how well your body transports oxygen to your muscles, and how well your muscles are able to absorb the oxygen during exercise.
For the study, 2,747 healthy people with an average age of 25 underwent treadmill tests the first year of the study and then again 20 years later. Cognitive tests taken 25 years after the start of the study measured verbal memory, psychomotor speed (the relationship between thinking skills and physical movement) and executive function.
For the treadmill test, which was similar to a cardiovascular stress test, participants walked or ran as the speed and incline increased until they could not continue or had symptoms such as shortness of breath. At the first test, participants lasted an average of 10 minutes on the treadmill. Twenty years later, that number decreased by an average of 2.9 minutes. For every additional minute people completed on the treadmill at the first test, they recalled 0.12 more words correctly on the memory test of 15 words and correctly replaced 0.92 more numbers with meaningless symbols in the test of psychomotor speed 25 years later, even after adjusting for other factors such as smoking, diabetes and high cholesterol.
People who had smaller decreases in their time completed on the treadmill test 20 years later were more likely to perform better on the executive function test than those who had bigger decreases. Specifically, they were better able to correctly state ink color (for example, for the word “yellow” written in green ink, the correct answer was “green”).
“These changes were significant, and while they may be modest, they were larger than the effect from one year of aging,” Jacobs said. “Other studies in older individuals have shown that these tests are among the strongest predictors of developing dementia in the future. One study showed that every additional word remembered on the memory test was associated with an 18-percent decrease in the risk of developing dementia after 10 years.”
“These findings are likely to help us earlier identify and consequently prevent or treat those at high risk of developing dementia,” Jacobs said.
New MIT technique could help decipher genes’ roles in learning and memory
Doctors commonly use magnetic resonance imaging (MRI) to diagnose tumors, damage from stroke, and many other medical conditions. Neuroscientists also rely on it as a research tool for identifying parts of the brain that carry out different cognitive functions.
Now, a team of biological engineers at MIT is trying to adapt MRI to a much smaller scale, allowing researchers to visualize gene activity inside the brains of living animals. Tracking these genes with MRI would enable scientists to learn more about how the genes control processes such as forming memories and learning new skills, says Alan Jasanoff, an MIT associate professor of biological engineering and leader of the research team.
“The dream of molecular imaging is to provide information about the biology of intact organisms, at the molecule level,” says Jasanoff, who is also an associate member of MIT’s McGovern Institute for Brain Research. “The goal is to not have to chop up the brain, but instead to actually see things that are happening inside.”
To help reach that goal, Jasanoff and colleagues have developed a new way to image a “reporter gene” — an artificial gene that turns on or off to signal events in the body, much like an indicator light on a car’s dashboard. In the new study, the reporter gene encodes an enzyme that interacts with a magnetic contrast agent injected into the brain, making the agent visible with MRI. This approach, described in a recent issue of the journal Chemical Biology, allows researchers to determine when and where that reporter gene is turned on.
An on/off switch
MRI uses magnetic fields and radio waves that interact with protons in the body to produce detailed images of the body’s interior. In brain studies, neuroscientists commonly use functional MRI to measure blood flow, which reveals which parts of the brain are active during a particular task. When scanning other organs, doctors sometimes use magnetic “contrast agents” to boost the visibility of certain tissues.
The new MIT approach includes a contrast agent called a manganese porphyrin and the new reporter gene, which codes for a genetically engineered enzyme that alters the electric charge on the contrast agent. Jasanoff and colleagues designed the contrast agent so that it is soluble in water and readily eliminated from the body, making it difficult to detect by MRI. However, when the engineered enzyme, known as SEAP, slices phosphate molecules from the manganese porphyrin, the contrast agent becomes insoluble and starts to accumulate in brain tissues, allowing it to be seen.
The natural version of SEAP is found in the placenta, but not in other tissues. By injecting a virus carrying the SEAP gene into the brain cells of mice, the researchers were able to incorporate the gene into the cells’ own genome. Brain cells then started producing the SEAP protein, which is secreted from the cells and can be anchored to their outer surfaces. That’s important, Jasanoff says, because it means that the contrast agent doesn’t have to penetrate the cells to interact with the enzyme.
Researchers can then find out where SEAP is active by injecting the MRI contrast agent, which spreads throughout the brain but accumulates only near cells producing the SEAP protein.
Exploring brain function
In this study, which was designed to test this general approach, the detection system revealed only whether the SEAP gene had been successfully incorporated into brain cells. However, in future studies, the researchers intend to engineer the SEAP gene so it is only active when a particular gene of interest is turned on.
Jasanoff first plans to link the SEAP gene with so-called “early immediate genes,” which are necessary for brain plasticity — the weakening and strengthening of connections between neurons, which is essential to learning and memory.
“As people who are interested in brain function, the top questions we want to address are about how brain function changes patterns of gene expression in the brain,” Jasanoff says. “We also imagine a future where we might turn the reporter enzyme on and off when it binds to neurotransmitters, so we can detect changes in neurotransmitter levels as well.”
Assaf Gilad, an assistant professor of radiology at Johns Hopkins University, says the MIT team has taken a “very creative approach” to developing noninvasive, real-time imaging of gene activity. “These kinds of genetically engineered reporters have the potential to revolutionize our understanding of many biological processes,” says Gilad, who was not involved in the study.
Sensing subtle differences in the environment
The hippocampus is an important region of the brain that encodes spatial memory. It consists of a number of subfields that have specialized functions in memory storage and retrieval, but the precise role of some of the subfields remains unclear. Thomas McHugh and colleagues from the Laboratory for Circuit and Behavioral Physiology at the RIKEN Brain Science Institute have now discovered that in mice, the CA2 subfield senses small changes in the environment that are at odds with their spatial memory.
McHugh and his colleagues sought to determine the role of each subfield of the hippocampus in sensing familiar and new environments through a series of mouse experiments, focusing on the often overlooked CA2 subfield. They first exposed mice to a familiar environment, and then moved them back to their home cage. The researchers then either put the mice back in the first location or moved them to a new location that the mice had never experienced.
The research team examined similarities and differences in the way hippocampal subfields responded to the two environments by a procedure known as catFISH—cellular compartment analysis of temporal activity by fluorescence in situ hybridization. This technique allows the timing of neuronal activity to be determined and permits the assessment of contextual memory by observing changes in response to environmental manipulations.
The researchers found that in most cases, there was more overlap in the response of hippocampal neurons in all subfields when the mice were replaced in the first location after their time in the home cage compared with placement in the new location. However, in mice with a mutation in the CA3 subfield that causes CA3 neuronal activity to be uncoupled from the animal’s sensory environment, the change in CA2 response to a novel environment did not appear. The finding suggests that the CA3 inputs to CA2 modulate the ability of CA2 to sense novel environments.
In a final experiment, the researchers introduced more subtle changes to the environments during the second placement by taking objects from one location to the other. A distinct change in CA2 neuronal activity was found during these exposure intervals as a response to more subtle changes to the animals’ environment. The CA2 subfield may therefore be the most sensitive to subtle differences between existing memories and new experiences. “In future studies, we plan to use genetic approaches to control CA2 activity in order to understand its direct effect on behavior,” says McHugh.
Genetic factor contributes to forgetfulness
University of Bonn psychologists prove genetic variation is underlying factor in higher incidence of forgetfulness
Misplaced your keys? Can’t remember someone’s name? Didn’t notice the stop sign? Those who frequently experience such cognitive lapses now have an explanation. Psychologists from the University of Bonn have found a connection between such everyday lapses and the DRD2 gene. Those who have a certain variant of this gene are more easily distracted and experience a significantly higher incidence of lapses due to a lack of attention. The scientific team will probably report their results in the May issue of “Neuroscience Letters,” which is already available online in advance.
Most of us are familiar with such everyday lapses; can’t find your keys, again! Or you walk into another room but forgot what you actually went there for. Or you are on the phone with someone and cannot remember their name. “Such short-term memory lapses are very common, but some people experience them particularly often,” said Prof. Dr. Martin Reuter from the department for Differential and Biological Psychology at the University of Bonn. Mistakes occurring due to such short-term lapses can become a hazard in cases where, e.g., a person overlooks a stop sign at an intersection. And in the workplace, a lack of attention can also become a problem–so for example when it results in forgetting to save essential data.
A gene “directing” your brain
"A familial clustering of such lapses suggests that they are subject to genetic effects," explained Dr. Sebastian Markett, the principal author and a member of Prof. Reuter’s team. In lab experiments, the group of scientists had already found indications earlier that the so-called dopamine D2 receptor gene (DRD2) plays a part in forgetfulness. DRD2 has an essential function in signal transmission within the frontal lobes. "This structure can be compared to a director coordinating the brain like an orchestra," Dr. Markett added. In this simile, the DRD2 gene would correspond to the baton, because it plays a part in dopamine transmission in the brain. If the baton skips a beat, the orchestra gets confused.
The psychologists from the University of Bonn tested a total of 500 women and men by taking a saliva sample and examining it using methods from molecular biology. All humans carry the DRD2 gene, which comes in two variants that are distinguished by only one letter within the genetic code. The one variant has C (cytosine) in one locus, which is displaced by T (thymine) in the other. According to the research team’s analyses, about a quarter of the subjects exclusively had the DRD2 gene with the cytosine nucleobase, while three quarters were the genotype with at least one thymine base.
The scientists then wanted to find out whether this difference in the genetic code also had an effect on everyday behavior. By means of a self-assessment survey they asked the subjects to state how frequently they experience these lapses–how often they forgot names, misplaced their keys. The survey also included questions regarding certain impulsivity-related factors, such as how easily a subject was distracted from actual tasks at hand, and how long they were able to maintain their concentration.
Lapses can clearly be tied to the gene variant
The scientists used statistical methods to check whether it was possible to associate the forgetfulness symptoms elicited by means of the surveys to one of the DRD2 gene variants. The results showed that functions such as attention and memory are less clearly expressed in persons who carry the thymine variant of the gene than in the cytosine type. “The connection is obvious; such lapses can partially be attributed to this gene variant,” reported Dr. Markett. According to their own statements, the subjects with the thymine DRD2 variant more frequently “fall victim” to forgetfulness or attention deficits. And vice versa, the cytosine type seems to be protected from that. “This result matches the results of other studies very well,” added Dr. Markett.
Carriers of the gene variant linked to forgetfulness may now find solace in the fact that they are not responsible for their genes, and that this is just their fate….but Dr. Markett doesn’t agree. “There are things you can do to compensate for forgetfulness; writing yourself notes or making more of an effort to put your keys down in a specific location–and not just anywhere.” Those who develop such strategies for the different areas of their lives are better able to handle their deficit.
(Source: www3.uni-bonn.de)
Rats’ brains may “remember” odor experienced while under general anesthesia
Rats’ brains may remember odors they were exposed to while deeply anesthetized, suggests research in rats published in the April issue of Anesthesiology.
Previous research has led to the belief that sensory information is received by the brain under general anesthesia but not perceived by it. These new findings suggest the brain not only receives sensory information, but also registers the information at the cellular level while anesthetized without behavioral reporting of the same information after recovering from anesthesia.
In the study, rats were exposed to a specific odor while under general anesthesia. Examination of the brain tissue after they had recovered from anesthesia revealed evidence of cellular imprinting, even though the rats behaved as if they had never encountered the odor before.
“It raises the question of whether our brains are being imprinted during anesthesia in ways we don’t recognize because we simply don’t remember,” said Yan Xu, Ph.D., lead author and vice chairman for basic sciences in the Department of Anesthesiology at the University of Pittsburgh School of Medicine. “The fact that an anesthetized brain can receive sensory information – and distinguish whether that information is novel or familiar during and after anesthesia, even if one does not remember receiving it – suggests a need to re-evaluate how the depth of anesthesia should be measured clinically.”
Researchers randomly assigned 107 rats to 12 different anesthesia and odor exposure paradigms: some were exposed to the same odor during and after anesthesia, some to air before and an odor after, some to familiar odors, others to novel odors, and still others were not exposed to odors at all. After the rats had recovered from the anesthesia, researchers observed their behavior of looking for hidden odors or interacting with scented beads to determine their memory of the smell. Researchers then analyzed the rats’ brains at a cellular level. While the rats had no memory of being exposed to the odor under anesthesia, changes in the brain tissue on a cellular level suggested the rats “remembered” the exposure to the odor under anesthesia and no longer registered the odor as novel.
“This study reveals important new information about how anesthesia affects our brains,” said Dr. Xu. “The results highlight a need for additional research into the effects of general anesthesia on learning and memory.”
The study, part-funded by the Medical Research Council (MRC) and published online in PNAS, challenges the idea that suppressed memories remain fully preserved in the brain’s unconscious, allowing them to be inadvertently expressed in someone’s behaviour. The results of the study suggest instead that the act of suppressing intrusive memories helps to disrupt traces of the memories in the parts of the brain responsible for sensory processing.
The team at the MRC Cognition and Brain Sciences Unit and the University of Cambridge’s Behavioural and Clinical Neuroscience Institute (BCNI) have examined how suppression affects a memory’s unconscious influences in an experiment that focused on suppression of visual memories, as intrusive unwanted memories are often visual in nature.
After a trauma, most people report intrusive memories or images, and people will often try to push these intrusions from their mind, as a way to cope. Importantly, the frequency of intrusive memories decreases over time for most people. It is critical to understand how the healthy brain reduces these intrusions and prevents unwanted images from entering consciousness, so that researchers can better understand how these mechanisms may go awry in conditions such as post-traumatic stress disorder.
Participants were asked to learn a set of word-picture pairs so that, when presented with the word as a reminder, an image of the object would spring to mind. After learning these pairs, brain activity was recorded using functional magnetic resonance imaging (fMRI) while participants either thought of the object image when given its reminder word, or instead tried to stop the memory of the picture from entering their mind.
The researchers studied whether suppressing visual memories had altered people’s ability to see the content of those memories when they re-encountered it again in their visual worlds. Without asking participants to consciously remember, they simply asked people to identify very briefly displayed objects that were made difficult to see by visual distortion. In general, under these conditions, people are better at identifying objects they have seen recently, even if they do not remember seeing the object before—an unconscious influence of memory. Strikingly, they found that suppressing visual memories made it harder for people to later see the suppressed object compared to other recently seen objects.
Brain imaging showed that people’s difficulty seeing the suppressed object arose because suppressing the memory from conscious awareness in the earlier memory suppression phase had inhibited activity in visual areas of the brain, disrupting visual memories that usually help people to see better. In essence, suppressing something from the mind’s eye had made it harder to see in the world, because visual memories and seeing rely on the same brain areas: out of mind, out of sight.
Over the last decade, research has shown that suppressing unwanted memories reduces people’s ability to consciously remember the experiences. The researchers’ studies on memory suppression have been inspired, in part, by trying to understand how people adapt memory after psychological trauma. Although this may work as a coping mechanism to help people adapt to the trauma, there is the possibility that if the memory traces were able to exert an influence on unconscious behaviour, they could potentially exacerbate mental health problems. The idea that suppression leaves unconscious memories that undermine mental health has been influential for over a century, beginning with Sigmund Freud.
These findings challenge the assumption that, even when supressed, a memory remains fully intact, which can then be expressed unconsciously. Moreover, this discovery pinpoints the neurobiological mechanisms underlying how this suppression process happens, and could inform further research on uncontrolled ‘intrusive memories’, a classic characteristic of post-traumatic stress disorder.
Dr Michael Anderson, at the MRC Cognition and Brain Sciences Unit said: “While there has been a lot of research looking at how suppression affects conscious memory, few studies have examined the influence this process might have on unconscious expressions of memory in behaviour and thought. Surprisingly, the effects of suppression are not limited to conscious memory. Indeed, it is now clear, that the influence of suppression extends beyond areas of the brain associated with conscious memory, affecting perceptual traces that can influence us unconsciously. This may contribute to making unwanted visual memories less intrusive over time, and perhaps less vivid and detailed.”
Dr Pierre Gagnepain, lead author at INSERM in France said: “Our memories can be slippery and hard to pin down. Out of hand and uncontrolled, their remembrance can haunt us and cause psychological troubles, as we see in PTSD. We were interested whether the brain can genuinely suppress memories in healthy participants, even at the most unconscious level, and how it might achieve this. The answer is that it can, though not all people were equally good at this. The better understanding of the neural mechanisms underlying this process arising from this study may help to better explain differences in how well people adapt to intrusive memories after a trauma”