How associative fear memory is formed in the brain
March 13, 2020
Science Daily/University of California - Riverside
How does the brain form "fear memory" that links a traumatic event to a particular situation? A pair of researchers at the University of California, Riverside, may have found an answer.
Using a mouse model, the researchers demonstrated the formation of fear memory involves the strengthening of neural pathways between two brain areas: the hippocampus, which responds to a particular context and encodes it, and the amygdala, which triggers defensive behavior, including fear responses.
Study results appear today in Nature Communications.
"It has been hypothesized that fear memory is formed by strengthening the connections between the hippocampus and amygdala," said Jun-Hyeong Cho, an assistant professor in the Department of Molecular, Cell and Systems Biology and the study's lead author. "Experimental evidence, however, has been weak. Our study now demonstrates for the first time that the formation of fear memory associated with a context indeed involves the strengthening of the connections between the hippocampus and amygdala."
According to Cho, weakening these connections could erase the fear memory.
"Our study, therefore, also provides insights into developing therapeutic strategies to suppress maladaptive fear memories in post-traumatic stress disorder patients," he said.
Post-traumatic stress disorder, or PTSD, affects 7% of the U.S. population. A psychiatric disorder that can occur in people who have experienced or witnessed a traumatic event, such as war, assault, or disaster, PTSD can cause problems in daily life for months, and even years, in affected persons.
Cho explained the capability of our brains to form a fear memory associated with a situation that predicts danger is highly adaptive since it enables us to learn from our past traumatic experiences and avoid those dangerous situations in the future. This process is dysregulated, however, in PTSD, where overgeneralized and exaggerated fear responses cause symptoms including nightmares or unwanted memories of the trauma, avoidance of situations that trigger memories of the trauma, heightened reactions, anxiety, and depressed mood.
"The neural mechanism of learned fear has an enormous survival value for animals, who must predict danger from seemingly neutral contexts," Cho said. "Suppose we had a car accident in a particular place and got severely injured. We would then feel afraid of that -- or similar -- place even long after we recover from the physical injury. This is because our brains form a memory that associates the car accident with the situation where we experienced the trauma. This associative memory makes us feel afraid of that, or similar, situation and we avoid such threatening situations."
According to Cho, during the car accident, the brain processes a set of multisensory circumstances around the traumatic event, such as visual information about the place, auditory information such as a crash sound, and smells of burning materials from damaged cars. The brain then integrates these sensory signals as a highly abstract form -- the context -- and forms a memory that associates the traumatic event with the context.
The researchers also plan to develop strategies to suppress pathological fear memories in PTSD.
https://www.sciencedaily.com/releases/2020/03/200313112137.htm
A good blood supply is good for memory
February 14, 2020
Science Daily/DZNE - German Center for Neurodegenerative Diseases
Memory performance and other cognitive abilities benefit from a good blood supply to the brain. This applies in particular to people affected by a condition known as "sporadic cerebral small vessel disease." Researchers of the German Center for Neurodegenerative Diseases (DZNE) and the University Medicine Magdeburg report on this in the journal "BRAIN." Their study suggests that blood perfusion of the so-called hippocampus could play a key role in age- and disease-related memory problems.
Inside the human brain there is a small structure, just a few cubic centimeters in size, which is called the "hippocampus" because its shape resembles a seahorse. Strictly speaking, the hippocampus exists twice: once in each brain hemisphere. It is considered the control center of memory. Damage to the hippocampus, such as it occurs in Alzheimer's and other brain diseases, is known to impair memory. But what role does blood supply in particular play? A team of scientists headed by Prof. Stefanie Schreiber and Prof. Emrah Duezel, both affiliated to the DZNE and the University Medicine Magdeburg, investigated this question. The researchers used high-resolution magnetic resonance imaging (MRI) to examine the blood supply to the hippocampus of 47 women and men aged 45 to 89 years. The study participants also underwent a neuropsychological test battery, which assessed, in particular, memory performance, speech comprehension and the abilty to concentrate.
A double supply line
"It has been known for some time that the hippocampus is supplied by either one or two arteries. It also happens that only one of the two hippocampi, which occur in every brain, is supplied by two vessels. This varies between individuals. The reasons are unknown," explained Schreiber. "Maybe there is a genetic predisposition. However, it is also possible that the individual structure of the blood supply develops due to life circumstances. Then the personal lifestyle would influence the blood supply to the hippocampus." In the cognition tests, those study participants in whom at least one hippocampus was doubly supplied generally scored better. "The fact that the blood supply is fundamentally important for the brain is certainly trivial and has been extensively documented. We were therefore particularly focused on the hippocampus and the situation of a disease of the brain vessels. Little is actually known about this."
Patients benefited in particular
Of the study subjects, 27 did not manifest signs of brain diseases. The remaining twenty participants showed pathological alterations in brain blood vessels, which were associated with microbleeding. "In these individuals, sporadic cerebral small vessel disease had been diagnosed prior to our investigations," said Dr. Valentina Perosa, lead author of the current study, who is currently doing postdoctoral research in Boston, USA. These individuals exhibited a broad spectrum of neurological anomalies, including mild cognitive impairment. "The healthy subjects generally scored better on cognitive tests than the study participants with small vessel disease. Among the participants with disease, those with at least one hippocampus supplied by two arteries reached better scores in cognition. They particularly benefited from the double supply. This may be due to a better supply not only of blood but also of oxygen. However, this is just a guess," said Perosa.
Starting point for therapies?
"Our study shows a clear link between blood supply to the hippocampus and cognitive performance," Schreiber summarised the results. "This suggests that brain blood flow might play a key role in the declining of memory performance, whether caused by age or disease." Such findings help to understand disease mechanisms and can also be useful for the development of novel treatment options, she indicates: "At present we can only speculate, because we don't know, but it is possible that lifestyle has an influence on the formation of the blood vessels that supply the hippocampus. This would then be a factor that can be influenced and thus a potential approach for therapies and also for prevention. This is a topic we intend to investigate."
https://www.sciencedaily.com/releases/2020/02/200214134725.htm
Brain waves in mice change based on memory age
December 17, 2019
Science Daily/RIKEN
Researchers have discovered signatures in brain activity that allow them to tell old and new memories apart. The team analyzed recordings from mouse brains using a machine-leaning algorithm, which was able to accurately classify memories as recent or remote. They also found robust communication between a frontal brain region and the hippocampus, a link which may form a concrete mechanism that tracks the age of memories.
Identifying the location and persistence of memories in the brain has implications for cases of brain damage, memory loss, and clinical memory impairment. In this study, the researchers were interested in how different brain areas that contain memory traces interact, especially during memory recall. The anterior cingulate cortex (ACC) in the prefrontal brain is known to be anatomically connected to the hippocampus. The team wanted to study this connection more closely, at the level of signals from individual neurons.
They recorded activity in both brain areas before exposing mice to a memory-forming experience (a foot shock), and then again in the same cage both one day and one month later. If mice froze in the same context, it was a behavioral indication that they remembered the shock. But the neuronal recordings also revealed that the ACC and hippocampus, specifically area CA1, are highly synchronized when mice recall the fear memory.
The interactions of the two brain areas changed over time, with ACC and CA1 activity becoming more correlated when an old or 'remote' memory was recalled compared to the recent, one-day memory. Specific frequencies and modes of neural activity became more pronounced between the two areas when the mice recalled the older memory, with the ACC appearing to drive activity in hippocampus in a top-down manner. "While memory is consolidated over time in frontal areas, we think in this case the ACC is facilitating the retrieval of contextual details back from the hippocampus," said senior author and team leader Thomas McHugh of RIKEN CBS.
The evolving pattern of signals over time allowed the researchers to distinguish old and new memories in mice from the brain recordings alone. "We could decode whether a mouse was recalling a recent or remote memory by looking at the correlations in ACC-CA1 interactions," said McHugh. Moreover, the researchers suggest that a small group of CA1 neurons carries the information about memory age.
"While we have known for 20 years that the ACC is important for recalling older memories, how it contributes has remained a mystery" McHugh explained. "We found that it plays in important role in organizing activity in the hippocampus, the part of the brain in which the memory was originally formed. This suggests the hippocampus always plays a role in providing key details of an old experience, at least in the healthy brain."
The team is now focused on understanding how impairments in long-term memory that often accompany aging and disease impacts activity in these brain circuits.
https://www.sciencedaily.com/releases/2019/12/191217114229.htm
What makes memories stronger?
Researchers shed new light on how the brain solidifies important memories
April 29, 2019
Science Daily/VIB (the Flanders Institute for Biotechnology)
A team of scientists at NeuroElectronics Research Flanders (NERF- empowered by imec, KU Leuven and VIB) found that highly demanding and rewarding experiences result in stronger memories. By studying navigation in rats, the researchers traced back the mechanism behind this selective memory enhancement to so-called replay processes in the hippocampus, the memory-processing center of the brain. These important findings provide new insights into one of the most enigmatic brain features: memory consolidation.
When we experience something important, we usually remember it better over time. This enhanced memory can be the result of stronger memory encoding during the experience, or because of memory consolidation that takes place after the experience. For example, experiences that turn out to be very rewarding have been found to lead to stronger and longer-lasting memories.
"One of the ways in which our brains consolidate memories is by mentally reliving the experience," explains Prof. Fabian Kloosterman, whose research is aimed at unravelling memory processing in the brain. "In biological terms, this boils down to the reactivation or replay of the neuronal activity patterns associated with a certain experience. This replay occurs in hippocampal-cortical brain networks during rest or sleep."
The question Kloosterman and his team at NERF set out to answer was whether the positive effect of rewards on hippocampal replay extend beyond the time of the experience itself and thus could further support enhanced memory consolidation.
Rewards and challenges
To find answers, the researchers trained rats to learn two goal locations in a familiar setting. One of the goals was a large reward -- nine food pellets -- while the other goal location only had a single food pellet on offer as a small reward. "Perhaps unsurprisingly, we found that rats remembered better the location where they found the large reward," says Frédéric Michon, PhD student in the Kloosterman lab, who conducted the experiments. "But we also observed that this reward-related effect on memory was strongest when the food pellets were located in places that required more complex memory formation."
Replay for better memory
To assess the contribution of replay brain activity after the actual experience, the researchers disrupted this particular signaling network, but only after the rats got a chance to discover the reward locations. Michon: "Mirroring our earlier findings, we observed that memory was impaired only for the highly rewarded locations, and in particular, when the rewards were at challenging locations."
In sum, the researchers could demonstrate that hippocampal replay, occurring after initial learning, contributes to the consolidation of highly rewarded experiences, and that this effect depends on the difficulty of a task. "A relatively simple experimental setting with rats and food pellets can teach us a lot about memory," says Kloosterman. "Our results demonstrate that replay contributes to the finely tuned selective consolidation of memories. Such insights could open future opportunities for treatments that help to strengthen memories, and could also help us understand memory decline in diseases such as dementia."
https://www.sciencedaily.com/releases/2019/04/190429111840.htm
Broken heart' syndrome may originate in the brain
March 4, 2019
Science Daily/European Society of Cardiology
Scientists have shown for the first time that the brain is involved in the development of a heart condition called Takotsubo syndrome (TTS). They found that regions of the brain responsible for processing emotions and controlling the unconscious workings of the body, such as heart beat, breathing and digestion, do not communicate with each other as well in TTS patients as in healthy people.
The study is published in the European Heart Journal today (Tuesday) and the researchers say that although, at this stage, they cannot show that the reduced brain functions definitely cause TTS, their findings suggest that these alterations in the central nervous system may be part of the mechanism involved and they are linked with the onset of TTS in response to stressful or emotional triggers.
TTS is known as "broken heart" syndrome and is characterised by a sudden temporary weakening of the heart muscles that causes the left ventricle of the heart to balloon out at the bottom while the neck remains narrow, creating a shape resembling a Japanese octopus trap, from which it gets its name. Since this relatively rare condition was first described in 1990, evidence has suggested that it is typically triggered by episodes of severe emotional distress, such as grief, anger or fear, or reactions to happy or joyful events. Patients develop chest pains and breathlessness, and it can lead to heart attacks and death. TTS is more common in women with only 10% of cases occurring in men. [1]
In an unusual example of collaboration between neuroscientists and cardiologists, researchers carried out MRI brain scans in 15 TTS patients taken from the InterTAK Registry, established at the University Hospital Zurich, Switzerland, in 2011 [2]. They compared the scans with those from 39 healthy people. The scans were performed between July 2013 and July 2014 and the average time between TTS diagnosis and the MRI scans was about a year.
Professor Christian Templin, principle investigator at the Registry and professor of cardiology at University Hospital Zurich, said: "We were interested in four specific brain regions that are spatially separate from one another but functionally connected, meaning they share information. We found that TTS patients had decreased communication between brain regions associated with emotional processing and the autonomic nervous system, which controls the unconscious workings of the body, compared to the healthy people.
"For the first time, we have identified a correlation between alterations to the functional activity of specific brain regions and TTS, which strongly supports the idea that the brain is involved in the underlying mechanism of TTS. Emotional and physical stress are strongly associated with TTS, and it has been hypothesised that the overstimulation of the autonomic nervous system may lead to TTS events."
The regions of the brain that the researchers looked at included the amygdala, hippocampus and cingulate gyrus, which control emotions, motivation, learning and memory. The amygdala and cingulate gyrus are also involved in the control of the autonomic nervous system and regulating heart function. In addition, the cingulate gyrus is involved in depression and other mood disorders that are common among TTS patients.
"Importantly, the regions we've identified as communicating less with one another in TTS patients are the same brain regions that are thought to control our response to stress. Therefore, this decrease in communication could negatively affect the way patients respond to stress and make them more susceptible to developing TTS," said Professor Templin.
A limitation of the study is that the researchers did not have MRI scans of patients' brains before or at the time they developed TTS, so cannot say for certain that the decreased communication between brain regions caused the TTS or vice versa.
Co-author, Dr Jelena Ghadri, a senior research associate at the University Hospital Zurich and co-principle investigator of the InterTAK Registry, said: "Our results suggest that additional studies should be conducted to determine whether this is a causal relationship. We hope this study offers new starting points for studying TTS in terms of understanding that it much more than 'broken heart' syndrome and clearly involves interactions between the brain and the heart, which are still not fully understood. We are at the beginning of learning more about this complex disorder. Hopefully, one day new findings can be translated into developments in preventive, therapeutic and diagnostic strategies to improve patient care.
"Of note, this study presents the results of a collaboration between neuroscientists and cardiologists. One problem in TTS research is that usually cardiologists only focus on the heart; we believe that approaching TTS in a multidisciplinary way might help to uncover the real nature and causes of this disease. The methods we used are mainly neuroscientific in nature, but the findings we uncovered are, in our view, of major importance for cardiologists in understanding TTS."
[1] TTS affects less than 3% of people who suffer a heart attack and tends to occur between the ages of 60-75.
[2] The InterTAK Registry is a worldwide network, including more than 40 different cardiology centres in more than 18 countries. The University Hospital Zurich has become a centre of excellence, specialising in the care of TTS patients, while also carrying out translational and basic science research.
https://www.sciencedaily.com/releases/2019/03/190304195238.htm
Scientists shed light on processes behind age-related decline in brain structures
January 31, 2019
Science Daily/Cardiff University
Aging can cause damage to support cells in the white matter, which in turn may lead to damage in the grey matter of the hippocampus, finds a new study.
The discovery gives researchers a new area to focus on in the search for treatments that can protect cognitive function.
Claudia Metzler-Baddeley, from Cardiff University's Brain Imaging Research Centre (CUBRIC), said: "The brain is made up of grey and white matter. While grey matter contains neuronal cells, which perform computations in our brain, the white matter contains connections and support cells that help the communication between different areas.
"Our new study not only confirms that aging leads to both grey matter decline in the hippocampus and white matter decline in the surrounding area, but also reveals the causal relationship between the two.
"Using a method called mediation analysis, we discovered that ageing of the white matter was accounting for ageing of hippocampal grey matter and not the other way around. Our results suggest that damage to the support cells may affect tissue health in the hippocampus, a region important for memory and involved in Alzheimer's disease.
"This is an exciting find. If hard-working support cells in the white matter start to misfunction with age, then therapies that protect these support cells may aid in the fight against the damage that ageing can do to our cognitive ability."
The study, which looked at the brains of 166 healthy volunteers, was carried out using state-of-the-art brain imaging techniques at CUBRIC and was jointly funded by the Alzheimer's Society and the BRACE Alzheimer's charity.
https://www.sciencedaily.com/releases/2019/01/190131104936.htm
Physical activity keeps hippocampus healthy those at risk for Alzheimer's disease
April 23, 2014
Science Daily/University of Maryland
A study of older adults at increased risk for Alzheimer's disease shows that moderate physical activity may protect brain health and stave off shrinkage of the hippocampus- the brain region responsible for memory and spatial orientation that is attacked first in Alzheimer's disease. Dr. J. Carson Smith, a kinesiology researcher in the University of Maryland School of Public Health who conducted the study, says that while all of us will lose some brain volume as we age, those with an increased genetic risk for Alzheimer's disease typically show greater hippocampal atrophy over time. The findings are published in the open-access journal Frontiers in Aging Neuroscience.
"The good news is that being physically active may offer protection from the neurodegeneration associated with genetic risk for Alzheimer's disease," Dr. Smith suggests. "We found that physical activity has the potential to preserve the volume of the hippocampus in those with increased risk for Alzheimer's disease, which means we can possibly delay cognitive decline and the onset of dementia symptoms in these individuals. Physical activity interventions may be especially potent and important for this group."
Dr. Smith and colleagues, including Dr. Stephen Rao from the Cleveland Clinic, tracked four groups of healthy older adults ages 65-89, who had normal cognitive abilities, over an 18-month period and measured the volume of their hippocampus (using structural magnetic resonance imaging, or MRI) at the beginning and end of that time period. The groups were classified both for low or high Alzheimer's risk (based on the absence or presence of the apolipoprotein E epsilon 4 allele) and for low or high physical activity levels.
Of all four groups studied, only those at high genetic risk for Alzheimer's who did not exercise experienced a decrease in hippocampal volume (3%) over the 18-month period. All other groups, including those at high risk for Alzheimer's but who were physically active, maintained the volume of their hippocampus.
"This is the first study to look at how physical activity may impact the loss of hippocampal volume in people at genetic risk for Alzheimer's disease," says Dr. Kirk Erickson, an associate professor of psychology at the University of Pittsburgh. "There are no other treatments shown to preserve hippocampal volume in those that may develop Alzheimer's disease. This study has tremendous implications for how we may intervene, prior to the development of any dementia symptoms, in older adults who are at increased genetic risk for Alzheimer's disease."
Individuals were classified as high risk for Alzheimer's if a DNA test identified the presence of a genetic marker -- having one or both of the apolipoprotein E-epsilon 4 allele (APOE-e4 allele) on chromosome 19 -- which increases the risk of developing the disease. Physical activity levels were measured using a standardized survey, with low activity being two or fewer days/week of low intensity activity, and high activity being three or more days/week of moderate to vigorous activity.
"We know that the majority of people who carry the APOE-e4 allele will show substantial cognitive decline with age and may develop Alzheimer's disease, but many will not. So, there is reason to believe that there are other genetic and lifestyle factors at work," Dr. Smith says. "Our study provides additional evidence that exercise plays a protective role against cognitive decline and suggests the need for future research to investigate how physical activity may interact with genetics and decrease Alzheimer's risk."
Dr. Smith has previously shown that a walking exercise intervention for patients with mild cognitive decline improved cognitive function by improving the efficiency of brain activity associated with memory. He is planning to conduct a prescribed exercise intervention in a population of healthy older adults with genetic and other risk factors for Alzheimer's disease and to measure the impact on hippocampal volume and brain function.
http://www.sciencedaily.com/releases/2014/04/140423102746.htm
Regular aerobic exercise boosts memory area of brain in older women
April 8, 2014
Science Daily/BMJ-British Medical Journal
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 aging 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.
http://www.sciencedaily.com/releases/2014/04/140408213545.htm
Zinc regulates communication between brain cells
September 21, 2011
Science Daily/Duke University Medical Center
Zinc has been found to play a critical role in regulating communication between cells in the brain, possibly governing the formation of memories and controlling the occurrence of epileptic seizures.
A collaborative project between Duke University Medical Center researchers and chemists at the Massachusetts Institute of Technology has been able to watch zinc in action as it regulates communication between neurons in the hippocampus, where learning and memory processes occur -- and where disrupted communication may contribute to epilepsy.
"We discovered that zinc is essential to control the efficiency of communication between two critical populations of nerve cells in the hippocampus," said James McNamara, M.D., senior author and chair of the Department of Neurobiology at Duke. "This addresses a longstanding controversy in the field."
"Carefully controlling zinc's regulation of communication between these nerve cells is critical to both formation of memories and perhaps to occurrence of epileptic seizures," McNamara said.
http://www.sciencedaily.com/releases/2011/09/110921132334.htm
Sleep selectively stores useful memories: brain evaluates information based on future expectations
February 1, 2011
Science Daily/Society for Neuroscience
After a good night's sleep, people remember information better when they know it will be useful in the future, according to a new study in the Feb. 2 issue of The Journal of Neuroscience. The findings suggest that the brain evaluates memories during sleep and preferentially retains the ones that are most relevant.
"Our results show that memory consolidation during sleep indeed involves a basic selection process that determines which of the many pieces of the day's information is sent to long-term storage," Born said. "Our findings also indicate that information relevant for future demands is selected foremost for storage."
Some, but not all, of the volunteers were allowed to sleep between the time they learned the tasks and the tests. As the authors expected, the people who slept performed better than those who didn't. But more importantly, only the people who slept and knew a test was coming had substantially improved memory recall.
The researchers also recorded electroencephalograms (EEG) from the individuals who were allowed to sleep. They found an increase in brain activity during deep or "slow wave" sleep when the volunteers knew they would be tested for memory recall.
"The more slow wave activity the sleeping participants had, the better their memory was during the recall test 10 hours later," Born said. Scientists have long thought that sleep is important in memory consolidation. The authors suggest that the brain's prefrontal cortex "tags" memories deemed relevant while awake and the hippocampus consolidates these memories during sleep.
http://www.sciencedaily.com/releases/2011/02/110201172603.htm
Memory Links to 40 Winks
July 6, 2010
Science Daily/Washington University in St. Louis
When it comes to executing items on tomorrow's to-do list, it's best to think it over, then "sleep on it," say psychologists at Washington University in St. Louis.
People who sleep after processing and storing a memory carry out their intentions much better than people who try to execute their plan before getting to sleep. The researchers have shown that sleep enhances our ability to remember to do something in the future, a skill known as prospective memory.
Moreover, researchers studying the relationship between memory and sleep say that our ability to carry out our intentions is not so much a function of how firmly that intention has been embedded in our memories. Rather, the trigger that helps carry out our intentions is usually a place, situation or circumstance -- some context encountered the next day -- that sparks the recall of an intended action.
The researchers found that participants who tested in the morning following sleep overwhelmingly performed the prospective memory task better in the semantic category test, or context, than in the other two, and they found no such correlation in the group who tested sleepless.
The crux of the finding rests on the fact that the prospective memory instruction was given right after the semantic category practice. In this context, those who slept remembered the prospective memory intention better than in the other categories.
"Sleep promoted the remembering to do the prospective memory task when that one context was present, but not when some other context was present," McDaniel says. "That's because of temporal contiguity -- the fact that the participants were told to hit that 'Q' button right after they were exposed to the semantic category context.
"The idea is that the semantic category test is weakly associated with the prospective memory intention -- it's weakly floating around in the mind and becomes weakly associated with the prospective memory test," McDaniel says.
To return to the colleague and message analogy, because before sleeping you remembered you had a message to deliver to your colleague and you would see him in the conference room tomorrow, sleep enhances the likelihood that you will tell him in the conference room, but not in some other context, the office, elevator, the mail room, for example.
The researchers believe that the prospective memory process occurs during slow wave sleep -- an early pattern in the sleep cycle -- involving communication between the hippocampus and cortical regions. The hippocampus is very important in memory formation and reactivation and the cortical regions are keys to storing memories.
"We think that during slow wave sleep the hippocampus is reactivating these recently learned memories, taking them up and placing them in long-term storage regions in the brain," Scullin says. "The physiology of slow wave sleep seems very conducive to this kind of memory strengthening."
http://www.sciencedaily.com/releases/2010/06/100630162359.htm
To Learn Better, Take a Nap (and Don't Forget to Dream)
April 26, 2010
Science Daily/Beth Israel Deaconess Medical Center
It is by now well established that sleep can be an important tool when it comes to enhancing memory and learning skills. And now, a new study sheds light on the role that dreams play in this important process.
Led by scientists at Beth Israel Deaconess Medical Center (BIDMC), the new findings suggest that dreams may be the sleeping brain's way of telling us that it is hard at work on the process of memory consolidation, integrating our recent experiences to help us with performance-related tasks in the short run and, in the long run, translating this material into information that will have widespread application to our lives. The study is reported in the April 22 On-line issue of Current Biology.
"What's got us really excited, is that after nearly 100 years of debate about the function of dreams, this study tells us that dreams are the brain's way of processing, integrating and really understanding new information," explains senior author Robert Stickgold, PhD, Director of the Center for Sleep and Cognition at BIDMC and Associate Professor of Psychiatry at Harvard Medical School. "Dreams are a clear indication that the sleeping brain is working on memories at multiple levels, including ways that will directly improve performance."
To test this hypothesis, the investigators had 99 subjects spend an hour training on a "virtual maze task," a computer exercise in which they were asked to navigate through and learn the layout of a complex 3D maze with the goal of reaching an endpoint as quickly as possible. Following this initial training, participants were assigned to either take a 90-minute nap or to engage in quiet activities but remain awake. At various times, subjects were also asked to describe what was going through their minds, or in the case of the nappers, what they had been dreaming about. Five hours after the initial exercise, the subjects were retested on the maze task.
The results were striking.
The non-nappers showed no signs of improvement on the second test -- even if they had reported thinking about the maze during their rest period. Similarly, the subjects who napped, but who did not report experiencing any maze-related dreams or thoughts during their sleep period, showed little, if any, improvement. But, the nappers who described dreaming about the task showed dramatic improvement, 10 times more than that shown by those nappers who reported having no maze-related dreams.
"These dreamers described various scenarios -- seeing people at checkpoints in a maze, being lost in a bat cave, or even just hearing the background music from the computer game," explains first author Erin Wamsley, PhD, a postdoctoral fellow at BIDMC and Harvard Medical School. These interpretations suggest that not only was sleep necessary to "consolidate" the information, but that the dreams were an outward reflection that the brain had been busy at work on this very task.
Of particular note, say the authors, the subjects who performed better were not more interested or motivated than the other subjects. But, they say, there was one distinct difference that was noted.
"The subjects who dreamed about the maze had done relatively poorly during training," explains Wamsley. "Our findings suggest that if something is difficult for you, it's more meaningful to you and the sleeping brain therefore focuses on that subject -- it 'knows' you need to work on it to get better, and this seems to be where dreaming can be of most benefit."
Furthermore, this memory processing was dependent on being in a sleeping state. Even when a waking subject "rehearsed and reviewed" the path of the maze in his mind, if he did not sleep, then he did not see any improvement, suggesting that there is something unique about the brain's physiology during sleep that permits this memory processing.
"In fact," says Stickgold, "this may be one of the main goals that led to the evolution of sleep. If you remain awake [following the test] you perform worse on the subsequent task. Your memory actually decays, no matter how much you might think about the maze.
"We're not saying that when you learn something it is dreaming that causes you to remember it," he adds. "Rather, it appears that when you have a new experience it sets in motion a series of parallel events that allow the brain to consolidate and process memories."
Ultimately, say the authors, the sleeping brain seems to be accomplishing two separate functions: While the hippocampus is processing information that is readily understandable (i.e. navigating the maze), at the same time, the brain's higher cortical areas are applying this information to an issue that is more complex and less concrete (i.e. how to navigate through a maze of job application forms).
"Our [nonconscious] brain works on the things that it deems are most important," adds Wamsley. "Every day, we are gathering and encountering tremendous amounts of information and new experiences," she adds. "It would seem that our dreams are asking the question, 'How do I use this information to inform my life?'"
http://www.sciencedaily.com/releases/2010/04/100422153753.htm
Direct Evidence of Role of Sleep in Memory Formation is Uncovered
September 16, 2009
Science Daily/Rutgers University
A research team has pinpointed for the first time the mechanism that takes place during sleep that causes learning and memory formation to occur. The team has determined that short transient brain events, called “sharp wave ripples,” are responsible for consolidating memory and transferring the learned information from the hippocampus to the neocortex, where long-term memories are stored.
A Rutgers University, Newark and Collége de France, Paris research team has pinpointed for the first time the mechanism that takes place during sleep that causes learning and memory formation to occur.
It’s been known for more than a century that sleep somehow is important for learning and memory. Sigmund Freud further suspected that what we learned during the day was “rehearsed” by the brain during dreaming, allowing memories to form. And while much recent research has focused on the correlative links between the hippocampus and memory consolidation, what had not been identified was the specific processes that cause long-term memories to form.
“This is the first example that if a well-defined pattern of activity in the brain is reliably and selectively eliminated, it results in memory deficit; a demonstration that this specific brain pattern is the cause behind long-term memory formation,” says Buzsaki.
The research also represents a move toward a new direction in neuroscience research. While previous research largely has focused on correlating behavior with specific brain events through electroencephalogram, neuronal spiking and functional magnetic resonance imaging studies, increasingly researchers are challenging those correlations as they seek to identify the specific process or processes that cause certain events and behaviors to take place.
http://www.sciencedaily.com/releases/2009/09/090915174506.htm
Compound found in grapes, red wine may help prevent memory loss
February 4, 2015
Science Daily/Texas A&M University
A compound found in common foods such as red grapes and peanuts may help prevent age-related decline in memory, according to new research published by a faculty member in the Texas A&M Health Science Center College of Medicine.
Ashok K. Shetty, Ph.D., a professor in the Department of Molecular and Cellular Medicine and Director of Neurosciences at the Institute for Regenerative Medicine, has been studying the potential benefit of resveratrol, an antioxidant that is found in the skin of red grapes, as well as in red wine, peanuts and some berries.
Resveratrol has been widely touted for its potential to prevent heart disease, but Shetty and a team that includes other researchers from the health science center believe it also has positive effects on the hippocampus, an area of the brain that is critical to functions such as memory, learning and mood.
Because both humans and animals show a decline in cognitive capacity after middle age, the findings may have implications for treating memory loss in the elderly. Resveratrol may even be able to help people afflicted with severe neurodegenerative conditions such as Alzheimer's disease.
In a study published online Jan. 28 in Scientific Reports, Shetty and his research team members reported that treatment with resveratrol had apparent benefits in terms of learning, memory and mood function in aged rats.
"The results of the study were striking," Shetty said. "They indicated that for the control rats who did not receive resveratrol, spatial learning ability was largely maintained but ability to make new spatial memories significantly declined between 22 and 25 months. By contrast, both spatial learning and memory improved in the resveratrol-treated rats."
Shetty said neurogenesis (the growth and development of neurons) approximately doubled in the rats given resveratrol compared to the control rats. The resveratrol-treated rats also had significantly improved microvasculature, indicating improved blood flow, and had a lower level of chronic inflammation in the hippocampus.
"The study provides novel evidence that resveratrol treatment in late middle age can help improve memory and mood function in old age," Shetty said.
This study was funded primarily by the National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health. Shetty's lab is now examining the molecular mechanisms that underlie the improved cognitive function following resveratrol treatment. He also plans to conduct studies to see whether lower doses of resveratrol in the diet for prolonged periods would offer similar benefits to the aged brain.
Science Daily/SOURCE :http://www.sciencedaily.com/releases/2015/02/150204184230.htm