Posts tagged memory formation
Articles and news from the latest research reports.
A time for memories
Neuroscientists from the University of Leicester, in collaboration with the Department of Neurosurgery at the University California Los Angeles (UCLA), are to reveal details of how the brain determines the timing at which neurons in specific areas fire to create new memories.
This research exploits the unique opportunity of recording multiple single-neurons in patients suffering from epilepsy refractory to medication that are implanted with intracranial electrodes for clinical reasons.
The study, which is to be published in the academic journal Current Biology, is the result of collaboration between Professor Rodrigo Quian Quiroga and Dr Hernan Rey at the Centre for Systems Neuroscience at the University of Leicester and Professor Itzhak Fried at UCLA.
The work follows up on the group’s research into what was dubbed the ‘Jennifer Aniston neurons’ – neurons in the hippocampus and its surrounding areas within the brain that specifically fire in an ‘abstract’ manner when we see or hear a certain concept - such as a person, an animal or a landscape - that we recognise.
Professor Quian Quiroga said: “The firing of these neurons is relatively very late after the moment of seeing the picture, or hearing the person’s name, but is still very precise. These neurons also fire only when the pictures are consciously recognised and remain silent when they are not.
“Our research shows that there is a specific brain response that marks the timing of the firing of these neurons. This response shortly precedes the neuron’s firing and is only present for the consciously recognised pictures - being absent if the pictures were not recognised.
“This brain response thus reflects an activation that provides a temporal window for processing consciously perceived stimuli in the hippocampus and surrounding cortex. Given the proposed role of these neurons in memory formation, we argue that the brain response we found is a gateway for processing consciously perceived stimuli to form or recall memories.”
Dr Hernan Rey, first author of the study, added: “This time-keeping may indeed be critical for synchronizing and combining multisensory information involving different processing times. This, in turn, helps in creating a unified conceptual representation that can be used for memory functions.”
Professor Quian Quiroga’s work is specifically concerned with examining how information about the external world - what we see, hear and touch - is represented by neurons in the brain and how this leads to the creation of our own internal representations and memories.
For example, we can easily recognize a person in a fraction of a second, even when seen from different angles, with different sizes, colours, contrasts and under strikingly different conditions. But how neurons in the brain are capable of creating such an ‘abstract’ representation, disregarding basic visual details, is only starting to be known.
(Source: www2.le.ac.uk)
Cleveland Clinic identifies mechanism in Alzheimer’s-related memory loss
Cleveland Clinic researchers have identified a protein in the brain that plays a critical role in the memory loss seen in Alzheimer’s patients, according to a study to be published in the journal Nature Neuroscience and posted online today.
The protein – Neuroligin-1 (NLGN1) – is known to be involved in memory formation; this is the first time it’s been linked to amyloid-associated memory loss.
In Alzheimer’s disease, amyloid beta proteins accumulate in the brains of Alzheimer’s patients and induce inflammation. This inflammation leads to certain gene modifications that interrupt the functioning of synapses in the brain, leading to memory loss.
Using animal models, Cleveland Clinic researchers have discovered that during this neuroinflammatory process, the epigenetic modification of NLGN1 disrupts the synaptic network in the brain, which is responsible for developing and maintaining memories. Destroying this network can lead to the type of memory loss seen in Alzheimer’s patients.
"Alzheimer’s is a challenging disease that researchers have been approaching from all angles," said Mohamed Naguib, M.D., the Cleveland Clinic physician who lead the study. "This discovery could provide us with a new approach for preventing and treating Alzheimer’s disease."
Previous studies from this group of researchers have also identified a novel compound called MDA7, which can potentially stop the neuroinflammatory process that leads to the modification of NLGN1. Treatment with the compound restored cognition, memory and synaptic plasticity – a key neurological foundation of learning and memory – in an animal model. Significant preliminary work for the first-in-man study has been completed for MDA7 including in-vitro studies and preliminary clinical toxicology and pharmacokinetic work. The Cleveland Clinic plans to initiate Phase I human studies on the safety of this class of compounds in the near future.
Alzheimer’s disease is an irreversible, fatal brain disease that slowly destroys memory and thinking skills. About 5 million people in the United States have Alzheimer’s disease. With the aging of the population, and without successful treatment, there will be 16 million Americans and 106 million people worldwide with Alzheimer’s by 2050, according to the 2011 Alzheimer’s Disease Facts and Figures report from the Alzheimer’s Association.
(Source: eurekalert.org)
People with highly superior powers of recall also vulnerable to false memories
People who can accurately remember details of their daily lives going back decades are as susceptible as everyone else to forming fake memories, UC Irvine psychologists and neurobiologists have found.
In a series of tests to determine how false information can manipulate memory formation, the researchers discovered that subjects with highly superior autobiographical memory logged scores similar to those of a control group of subjects with average memory.
“Finding susceptibility to false memories even in people with very strong memory could be important for dissemination to people who are not memory experts. For example, it could help communicate how widespread our basic susceptibility to memory distortions is,” said Lawrence Patihis, a graduate student in psychology & social behavior at UC Irvine. “This dissemination could help prevent false memories in the legal and clinical psychology fields, where contamination of memory has had particularly important consequences in the past.”
Patihis works in the research group of world-renowned psychologist Elizabeth Loftus, who pioneered the study of false memories and their implications.
Persons with highly superior autobiographical memory (HSAM, also known as hyperthymesia) – which was first identified in 2006 by scientists at UC Irvine’s Center for the Neurobiology of Learning & Memory – have the astounding ability to remember even trivial details from their distant past. This includes recalling daily activities of their life since mid-childhood with almost 100 percent accuracy.
The lead researcher on the study, Patihis believes it’s the first effort to test malleable reconstructive memory in HSAM individuals.
Working with neurobiology & behavior graduate student Aurora LePort, Patihis asked 20 people with superior memory and 38 people with average memory to do word association exercises, recall details of photographs depicting a crime, and discuss their recollections of video footage of the United Flight 93 crash on 9/11. (Such footage does not exist.) These tasks incorporated misinformation in an attempt to manipulate what the subjects thought they had remembered.
“While they really do have super-autobiographical memory, it can be as malleable as anybody else’s, depending on whether misinformation was introduced and how it was processed,” Patihis said. “It’s a fascinating paradox. In the absence of misinformation, they have what appears to be almost perfect, detailed autobiographical memory, but they are vulnerable to distortions, as anyone else is.”
He noted that there are still many mysteries about people with highly superior autobiographical memory that need further investigation. LePort, for instance, is studying forgetting curves (which involve how many autobiographical details people can remember from one day ago, one week ago, one month ago, etc., and how the number of details decreases over time) in both HSAM and control participants and will employ functional MRI to better understand the phenomenon.
“What I love about the study is how it communicates something that memory distortion researchers have suspected for some time: that perhaps no one is immune to memory distortion,” Patihis said. “It will probably make some nonexperts realize, finally, that if even memory prodigies are susceptible, then they probably are too. This teachable moment is almost as important as the scientific merit of the study. It could help educate people – including those who deal with memory evidence, such as clinical psychologists and legal professionals – about false memories.”
The study appears this week in the early online version of Proceedings of the National Academy of Sciences.
How video gaming can be beneficial for the brain
Video gaming causes increases in the brain regions responsible for spatial orientation, memory formation and strategic planning as well as fine motor skills. This has been shown in a new study conducted at the Max Planck Institute for Human Development and Charité University Medicine St. Hedwig-Krankenhaus. The positive effects of video gaming may also prove relevant in therapeutic interventions targeting psychiatric disorders.
In order to investigate how video games affect the brain, scientists in Berlin have asked adults to play the video game “Super Mario 64” over a period of two months for 30 minutes a day. A control group did not play video games. Brain volume was quantified using magnetic resonance imaging (MRI). In comparison to the control group the video gaming group showed increases of grey matter, in which the cell bodies of the nerve cells of the brain are situated. These plasticity effects were observed in the right hippocampus, right prefrontal cortex and the cerebellum. These brain regions are involved in functions such as spatial navigation, memory formation, strategic planning and fine motor skills of the hands. Most interestingly, these changes were more pronounced the more desire the participants reported to play the video game.
“While previous studies have shown differences in brain structure of video gamers, the present study can demonstrate the direct causal link between video gaming and a volumetric brain increase. This proves that specific brain regions can be trained by means of video games”, says study leader Simone Kühn, senior scientist at the Center for Lifespan Psychology at the Max Planck Institute for Human Development. Therefore Simone Kühn and her colleagues assume that video games could be therapeutically useful for patients with mental disorders in which brain regions are altered or reduced in size, e.g. schizophrenia, post-traumatic stress disorder or neurodegenerative diseases such as Alzheimer’s dementia.
“Many patients will accept video games more readily than other medical interventions”, adds the psychiatrist Jürgen Gallinat, co-author of the study at Charité University Medicine St. Hedwig-Krankenhaus. Further studies to investigate the effects of video gaming in patients with mental health issues are planned. A study on the effects of video gaming in the treatment of post-traumatic stress disorder is currently ongoing.
Feelings forge stronger memories
Bad experiences enhance memory formation about places, scientists at The University of Queensland have found.
Dr Oliver Baumann from the Queensland Brain Institute found that associating negative imagery with specific locations activates a part of the brain responsible for forming memory of places during navigation – the parahippocampal cortex.
“This heightened recall occurs automatically, without people even being aware that the negative imagery is affecting their memories,” said Dr Baumann, who worked on the study in the QBI’s Mattingley lab.
“It could serve as a cue for avoiding potential threats,” Dr Baumann said.
“Our findings show that emotions can exert a powerful influence on spatial and navigational memory for places.
“In future we might be able to boost memory functions by triggering the positive side-effects of emotional arousal, while avoiding the need for negative experiences.”
For the research, Professor Jason Mattingley built a “virtual house” and staged events in each room unrelated to the subject navigating the house.
The events were designed to elicit an emotional response – positive, negative, or neutral, and varied in their rate of occurrence.
“The events were illustrated using images from the International Affective Picture System library and included dramatic scenes of attack and threat, as well as more pleasant imagery,” Dr Baumann said.
The day after navigating through the house, participants viewed static images of the house without the emotional imagery, while their neural activity was recorded using an MRI scanner.
“The results showed that emotional arousal exerted a powerful influence on memory by enhancing parahippocampal activity,” Dr Baumann said.
The study was published in the Journal of Cognitive Neuroscience.
(Source: uq.edu.au)
Study helps deconstruct estrogen’s role in memory
The loss of estrogens at menopause increases a woman’s risk of dementia and Alzheimer’s disease, yet hormone replacement therapy can cause harmful side effects.
Knowing the exact mechanism of estrogen activation in the brain could lead to new targets for drug development that would provide middle-aged women the cognitive benefits of hormone replacement therapy without increasing their risk for cardiovascular disease or breast cancer.
In a new study, Karyn Frick, professor of psychology at the University of Wisconsin-Milwaukee, uncovers details about estrogen’s role in the complex cellular communication system underlying memory formation.
“The receptor mechanisms that regulate estrogen’s ability to enhance memory are still poorly understood,” says Frick. “With this study, we’ve begun to sort out several of the key players needed for estrogens to mediate memory formation.”
The research, published in the The Journal of Neuroscience today, focused on estrogen effects in a brain region called the hippocampus, which deteriorates with age or Alzheimer’s disease. The researchers found that each of the two known estrogen receptors rapidly activate a specific cellular pathway necessary for memory formation in the hippocampus of female mice, but only if they interact with a certain glutamate receptor, called mGluR1.
The study revealed that when this glutamate receptor is blocked, the cell-signaling protein ERK cannot be activated by the potent estrogen, 17β-estradiol. Because ERK activation is necessary for memory formation, estradiol failed to enhance memory among mice in which mGluR1 was blocked.
Frick’s team also found evidence that estrogen receptors and mGluR1 physically interact at the cell membrane, allowing estradiol to influence memory formation within seconds to minutes. Collectively, the data provide the first evidence that the rapid signaling initiated by such interactions is essential for estradiol to enhance memory regulated by the hippocampus.
“Our data suggesting that interactions between estrogen receptors and mGluR1 at the cell membrane are critical for estradiol to enhance memory provides important new information about how estrogens regulate memory formation,” Frick says. “Because membrane proteins are better targets for drug development than proteins inside the cell, these data could lead to a new generation of therapies that provide the cognitive benefits of estrogens without harmful side effects.”
Modifying the activity of neuronal networks that encode spatial memories leads to the formation of an incorrect fear memory in mice
The formation and retrieval of memories allows all kinds of organisms, including humans, to learn and thrive in their environment. Yet our memories are not always accurate, and mistaken remembrances can have important consequences, such as in the justice system and in our navigation of the world. Susumu Tonegawa, Steve Ramirez, Xu Liu and colleagues at the RIKEN-MIT Center for Neural Circuit Genetics, have gained insight into the creation of mistaken memories by using light activation of neurons to generate an incorrect fear memory in mice.
The researchers allowed mice to explore a novel location and used genetic techniques to label neurons in the hippocampus—a part of the brain linked to spatial memory—that were activated in the process with a special channel called channelrhodopsin-2. The cells that expressed this channel could then be artificially activated by light. In this way, the researchers were able to reactivate neurons that fired in that particular location, even if the mice were no longer there.
They then moved the mice to another location where they were exposed to foot shocks, causing the mice to exhibit immobility, a fear behavior. At the same time, the researchers used light to activate the channelrhodopsin-2-expressing neurons that had fired in the first location.
When Tonegawa and his colleagues moved the animals to a third location, they did not show fear behavior. Yet when the mice went back to the first location, where they had never experienced a foot shock, the mice now exhibited prominent freezing behavior. The researchers had generated a ‘false memory’ in the mice of foot shocks in a location in which they had never been exposed to them.
The researchers showed that light reactivation of neuronal networks in the central area of the hippocampus, called the dentate gyrus, could create false memories, while reactivation of the outer ‘CA1’ area of the hippocampus could not. Tonegawa and his colleagues suggest that this is because mouse exploration of different locations leads to activation of more overlapping neuronal networks in the CA1 than in the dentate gyrus. “This may reflect the fundamental differences of how memories are encoded in these two regions,” explains Liu.
The findings provide insight into how the brain encodes and processes memories and could one day lead to treatments for post-traumatic stress disorder. “Our work may also have implications for situations where patients mix reality with their own imaginations, such as in schizophrenia,” says Liu.
Scientists Pinpoint Proteins Vital to Long-Term Memory
Scientists from the Florida campus of The Scripps Research Institute (TSRI) have found a group of proteins essential to the formation of long-term memories.
The study, published online ahead of print on September 12, 2013 by the journal Cell Reports, focuses on a family of proteins called Wnts. These proteins send signals from the outside to the inside of a cell, inducing a cellular response crucial for many aspects of embryonic development, including stem cell differentiation, as well as for normal functioning of the adult brain.
“By removing the function of three proteins in the Wnt signaling pathway, we produced a deficit in long-term but not short-term memory,” said Ron Davis, chair of the TSRI Department of Neuroscience. “The pathway is clearly part of the conversion of short-term memory to the long-term stable form, which occurs through changes in gene expression.”
The findings stem from experiments probing the role of Wnt signaling components in olfactory memory formation in Drosophila, the common fruit fly—a widely used doppelgänger for human memory studies. In the new study, the scientists inactivated the expression of several Wnt signaling proteins in the mushroom bodies of adult flies—part of the fly brain that plays a role in learning and memory.
The resulting memory disruption, Davis said, suggests that Wnt signaling participates actively in the formation of long-term memory, rather than having some general, non-specific effect on behavior.
“What is interesting is that the molecular mechanisms of adult memory use the same processes that guide the early development of the organism, except that they are repurposed for memory formation,” he said. “One difference, however, is that during early development the signals are intrinsic, while in adults they require an outside stimulus to create a memory.”
(Source: scripps.edu)
Study creates new memories by directly changing the brain
Findings could prove helpful in understanding and resolving learning and memory disorders
By studying how memories are made, UC Irvine neurobiologists created new, specific memories by direct manipulation of the brain, which could prove key to understanding and potentially resolving learning and memory disorders.
Research led by senior author Norman M. Weinberger, a research professor of neurobiology & behavior at UC Irvine, and colleagues has shown that specific memories can be made by directly altering brain cells in the cerebral cortex, which produces the predicted specific memory. The researchers say this is the first evidence that memories can be created by direct cortical manipulation. Study results appeared in the August 29 issue of Neuroscience.
During the research, Weinberger and colleagues played a specific tone to test rodents then stimulated the nucleus basalis deep within their brains, releasing acetylcholine (ACh), a chemical involved in memory formation. This procedure increased the number of brain cells responding to the specific tone. The following day, the scientists played many sounds to the animals and found that their respiration spiked when they recognized the particular tone, showing that specific memory content was created by brain changes directly induced during the experiment. Created memories have the same features as natural memories including long-term retention.
"Disorders of learning and memory are a major issue facing many people and since we’ve found not only a way that the brain makes memories, but how to create new memories with specific content, our hope is that our research will pave the way to prevent or resolve this global issue," said Weinberger, who is also a fellow with the Center for the Neurobiology of Learning & Memory and the Center for Hearing Research at UC Irvine.
The creation of new memories by directly changing the cortex is the culmination of several years of research in Weinberger’s lab implicating the nucleus basalis and ACh in brain plasticity and specific memory formation. Previously, the authors had also shown that the strength of memory is controlled by the number of cells in the auditory cortex that process a sound.
How parents see themselves may affect their child’s brain and stress level
Self-perceived social status predicts hippocampal function and stress hormones
A mother’s perceived social status predicts her child’s brain development and stress indicators, finds a study at Boston Children’s Hospital. While previous studies going back to the 1950s have linked objective socioeconomic factors — such as parental income or education — to child health, achievement and brain function, the new study is the first to link brain function to maternal self-perception.
In the study, children whose mothers saw themselves as having a low social status were more likely to have increased cortisol levels, an indicator of stress, and less activation of their hippocampus, a structure in the brain responsible for long-term memory formation (required for learning) and reducing stress responses.
Findings were published online August 6th by the journal Developmental Science, and will be part of a special issue devoted to the effects of socioeconomic status on brain development.
"We know that there are big disparities among people in income and education," says Margaret Sheridan, PhD, of the Labs of Cognitive Neuroscience at Boston Children’s Hospital, the study’s first author. "Our results indicate that a mother’s perception of her social status ‘lives’ biologically in her children."
Sheridan, senior investigator Charles Nelson, PhD, of Boston Children’s Hospital and colleagues studied 38 children aged 8.3 to 11.8 years. The children gave saliva samples to measure levels of cortisol, and 19 also underwent functional MRI of the brain, focusing on the hippocampus.
Mothers, meanwhile, rated their social standing on a ladder on a scale of 1 to 10, comparing themselves with others in the United States. Findings were as follows:
- After controlling for gender and age, the mother’s self-perceived social status was a significant predictor of cortisol levels in the child. This finding is consistent with studies in animals. “In animal research, your stress response is related to your relative standing in the hierarchy,” Sheridan says.
- Similarly, the mother’s perceived social status significantly predicted the degree of hippocampal activation in their children during a learning task.
- In contrast, actual maternal education or income-to-needs ratio (income relative to family size) did not significantly predict cortisol levels or hippocampal activation.
The findings suggest that while actual socioeconomic status varies, how people perceive and adapt to their situation is an important factor in child development. Some of this may be culturally determined, Sheridan notes. She is currently participating in a much larger international study of childhood poverty, the Young Lives Project, that is looking at objective and subjective measures of social status along with health measures and cognitive function. The study will capture much wider extremes of socioeconomic status than would a U.S.-based study.
What the current study didn’t find was evidence that stress itself alters hippocampal function; no relationship was found between cortisol and hippocampal function, as has been seen in animals, perhaps because of the small number children having brain fMRIs. “This needs further exploration,” says Sheridan. “There may be more than one pathway leading to differences in long-term memory, or there may be an effect of stress on the hippocampus that comes out only in adulthood.”
(Source: eurekalert.org)