Posts tagged psychology
Articles and news from the latest research reports.
To answer the seemingly simple question “Have I been here before?” we must use our memories of previous experiences to determine if our current location is familiar or novel. In a new study published in the Journal of Neuroscience researchers from the RIKEN Brain Science Institute have identified a region of the hippocampus, called CA2, which is sensitive to even small changes in a familiar context. The results provide the first clue to the contributions of CA2 to memory and may help shed light on why this area is often found to be abnormal in the schizophrenic brain.
Change comes in many flavors; if we move to a new country, city or house it is easy to recognize the novelty of the environment, but if we come home to find the furniture rearranged or a new piece of art on the wall, this recognition may be much slower. Scientists believe this is because memory formation requires comparing current information with previous experience and the larger the overlap, the more difficult the distinction. It has long been known that the hippocampus is a region of the brain crucial for this type of memory, however the identification of neurons responsible for this comparison has remained elusive.
In this study Marie Wintzer, Roman Boehringer, Denis Polygalov and Thomas McHugh used genetically modified mice and advanced cell imaging techniques to demonstrate that while the entire hippocampus is capable of detecting large changes in context, the small and often overlooked CA2 region is exquisitely sensitive to small changes.
Mice were familiarized with one context and then placed either in a much different context or back in the original with small alterations, such as several new small objects. By detecting the expression of activity induced genes Wintzer and colleagues were able to demonstrate that just a few new objects in the otherwise unchanged context completely altered the pattern of active cells specifically in CA2. Mice that had been genetically engineered to lack this CA2 response explored the new context much less than their normal siblings.
“CA2 has often been overlooked or simply grouped together with its more prominent neighbors, but these data suggest it’s unique and important for recognizing and reacting to changes in our environments” explains Dr. McHugh, the leader of the study.
Compared to rodents, human CA2 is proportionally larger, but still as mysterious. One intriguing finding has been that early in the onset of schizophrenia and bipolar disorder there is a loss of inhibitory neurons specifically in CA2. In addition to the memory problems that accompany these diseases, patients often exhibit a hyper-sensitivity to changes in environment and routine. This study suggests there may be a functional relationship between this sensitivity and CA2 dysfunction, hinting at a new circuit to target in our attempts to understand the function of both the normal and diseased brain.
Why does the brain remember dreams?
Some people recall a dream every morning, whereas others rarely recall one. A team led by Perrine Ruby, an Inserm Research Fellow at the Lyon Neuroscience Research Center (Inserm/CNRS/Université Claude Bernard Lyon 1), has studied the brain activity of these two types of dreamers in order to understand the differences between them. In a study published in the journal Neuropsychopharmacology, the researchers show that the temporo-parietal junction, an information-processing hub in the brain, is more active in high dream recallers. Increased activity in this brain region might facilitate attention orienting toward external stimuli and promote intrasleep wakefulness, thereby facilitating the encoding of dreams in memory.
The reason for dreaming is still a mystery for the researchers who study the difference between “high dream recallers,” who recall dreams regularly, and “low dream recallers,” who recall dreams rarely. In January 2013 (work published in the journal Cerebral Cortex), the team led by Perrine Ruby, Inserm researcher at the Lyon Neuroscience Research Center, made the following two observations: “high dream recallers” have twice as many time of wakefulness during sleep as “low dream recallers” and their brains are more reactive to auditory stimuli during sleep and wakefulness. This increased brain reactivity may promote awakenings during the night, and may thus facilitate memorisation of dreams during brief periods of wakefulness.
In this new study, the research team sought to identify which areas of the brain differentiate high and low dream recallers. They used Positron Emission Tomography (PET) to measure the spontaneous brain activity of 41 volunteers during wakefulness and sleep. The volunteers were classified into 2 groups: 21 “high dream recallers” who recalled dreams 5.2 mornings per week in average, and 20 “low dream recallers,” who reported 2 dreams per month in average. High dream recallers, both while awake and while asleep, showed stronger spontaneous brain activity in the medial prefrontal cortex (mPFC) and in the temporo-parietal junction (TPJ), an area of the brain involved in attention orienting toward external stimuli.
Brain Damage in Children—The Result of Too Many Chemicals?
A new report is sounding the alarm of a “silent epidemic” of childhood neurological disorders linked to neurotoxic compounds.
While genetics is known to play a role in neurological problems, only 30 to 40 percent of neurodevelopmental disorders can be definitively tied to family history. “There are a lot of chemicals out there that have been shown to have the capability to injure the developing brain,” says study coauthor Philip Landrigan, MD, professor and chair of the department of community and preventive medicine at Mount Sinai School of Medicine in New York City and one of the world’s foremost authorities on children’s environmental health. “And we’re very concerned that a number of chemicals in everyday products have never been properly tested to determine whether they’re toxic to the human brain.”
In the new report, Dr. Landrigan and his coauthor identified six chemicals that have been discovered, within the past seven years, to trigger brain damage in children. In 2006, he and other researchers ID’d lead, methylmercury, arsenic, polychlorinated biphenyls (PCBs), and toluene as known contributors to rising rates of neurodevelopmental disorders like autism, attention-deficit hyperactivity disorder, and learning disabilities.
Understanding the basic biology of bipolar disorder
Scientists know there is a strong genetic component to bipolar disorder, but they have had an extremely difficult time identifying the genes that cause it. So, in an effort to better understand the illness’s genetic causes, researchers at UCLA tried a new approach.
Instead of only using a standard clinical interview to determine whether individuals met the criteria for a clinical diagnosis of bipolar disorder, the researchers combined the results from brain imaging, cognitive testing, and an array of temperament and behavior measures. Using the new method, UCLA investigators — working with collaborators from UC San Francisco, Colombia’s University of Antioquia and the University of Costa Rica — identified about 50 brain and behavioral measures that are both under strong genetic control and associated with bipolar disorder. Their discoveries could be a major step toward identifying the specific genes that contribute to the illness.
The results are published in the Feb. 12 edition of the journal JAMA Psychiatry.
A severe mental illness that affects about 1 to 2 percent of the population, bipolar disorder causes unusual shifts in mood and energy, and it interferes with the ability to carry out everyday tasks. Those with the disorder can experience tremendous highs and extreme lows — to the point of not wanting to get out of bed when they’re feeling down. The genetic causes of bipolar disorder are highly complex and likely involve many different genes, said Carrie Bearden, a senior author of the study and an associate professor of psychiatry and psychology at the UCLA Semel Institute for Neuroscience and Human Behavior.
"The field of psychiatric genetics has long struggled to find an effective approach to begin dissecting the genetic basis of bipolar disorder," Bearden said. "This is an innovative approach to identifying genetically influenced brain and behavioral measures that are more closely tied to the underlying biology of bipolar disorder than the clinical symptoms alone are."
The researchers assessed 738 adults, 181 of whom have severe bipolar disorder. They used high-resolution 3-D images of the brain, questionnaires evaluating temperament and personality traits of individuals diagnosed with bipolar disorder and their non-bipolar relatives, and an extensive battery of cognitive tests assessing long-term memory, attention, inhibitory control and other neurocognitive abilities.
Approximately 50 of these measures showed strong evidence of being influenced by genetics. Particularly interesting was the discovery that the thickness of the gray matter in the brain’s temporal and prefrontal regions — the structures that are critical for language and for higher-order cognitive functions like self-control and problem-solving — were the most promising candidate traits for genetic mapping, based on both their strong genetic basis and association with the disease.
"These findings are really just the first step in getting us a little closer to the roots of bipolar disorder," Bearden said. "What was really exciting about this project was that we were able to collect the most extensive set of traits associated with bipolar disorder ever assessed within any study sample. These data will be a really valuable resource for the field."
The individuals assessed in this study are members of large families living in Costa Rica’s central valley and Antioquia, Colombia. The families were founded by European and native Amerindian populations about 400 years ago and have a very high incidence of bipolar disorder. The groups were chosen because they have remained fairly isolated since their founding and their genetics are therefore simpler for scientists to study than those of general populations.
The fact that the findings aligned so closely with those of previous, smaller studies in other populations was surprising even to the scientists, given the subjects’ unique genetic background and living environments.
"This suggests that even if the specific genetic variants we identify may be unique to this population, the biological pathways they disrupt are likely to also influence disease risk in other populations," Bearden said.
The researchers’ next step is to use the genomic data they collected from the families — including full genome sequences and gene expression data— to begin identifying the specific genes that contribute to risk for bipolar disorder. The researchers also plan to extend their investigation into the children and teens in these families. They hypothesize that many of the bipolar-related brain and behavioral differences found in adults with bipolar disorder had their origins in adolescent neurodevelopment.
Meditation helps pinpoint neurological differences between two types of love
These findings won’t appear on any Hallmark card, but romantic love tends to activate the same reward areas of the brain as cocaine, research has shown.
Now Yale School of Medicine researchers studying meditators have found that a more selfless variety of love — a deep and genuine wish for the happiness of others without expectation of reward — actually turns off the same reward areas that light up when lovers see each other.
“When we truly, selflessly wish for the well-being of others, we’re not getting that same rush of excitement that comes with, say, a tweet from our romantic love interest, because it’s not about us at all,” said Judson Brewer, adjunct professor of psychiatry at Yale now at the University of Massachusetts.
Brewer and Kathleen Garrison, postdoctoral researcher in Yale’s Department of Psychiatry, report their findings in a paper scheduled to be published online Feb. 12 in the journal Brain and Behavior.
The neurological boundaries between these two types of love become clear in fMRI scans of experienced meditators. The reward centers of the brain that are strongly activated by a lover’s face (or a picture of cocaine) are almost completely turned off when a meditator is instructed to silently repeat sayings such as “May all beings be happy.”
Such mindfulness meditations are a staple of Buddhism and are now commonly practiced in Western stress reduction programs, Brewer notes. The tranquility of this selfless love for others — exemplified in such religious figures such as Mother Theresa or the Dalai Llama — is diametrically opposed to the anxiety caused by a lovers’ quarrel or extended separation. And it carries its own rewards.
“The intent of this practice is to specifically foster selfless love — just putting it out there and not looking for or wanting anything in return,” Brewer said. “If you’re wondering where the reward is in being selfless, just reflect on how it feels when you see people out there helping others, or even when you hold the door for somebody the next time you are at Starbucks.”
New evidence that chronic stress predisposes brain to mental illness
University of California, Berkeley, researchers have shown that chronic stress generates long-term changes in the brain that may explain why people suffering chronic stress are prone to mental problems such as anxiety and mood disorders later in life.
Their findings could lead to new therapies to reduce the risk of developing mental illness after stressful events.
Doctors know that people with stress-related illnesses, such as post-traumatic stress disorder (PTSD), have abnormalities in the brain, including differences in the amount of gray matter versus white matter. Gray matter consists mostly of cells – neurons, which store and process information, and support cells called glia – while white matter is comprised of axons, which create a network of fibers that interconnect neurons. White matter gets its name from the white, fatty myelin sheath that surrounds the axons and speeds the flow of electrical signals from cell to cell.
How chronic stress creates these long-lasting changes in brain structure is a mystery that researchers are only now beginning to unravel.
In a series of experiments, Daniela Kaufer, UC Berkeley associate professor of integrative biology, and her colleagues, including graduate students Sundari Chetty and Aaron Freidman, discovered that chronic stress generates more myelin-producing cells and fewer neurons than normal. This results in an excess of myelin – and thus, white matter – in some areas of the brain, which disrupts the delicate balance and timing of communication within the brain.
“We studied only one part of the brain, the hippocampus, but our findings could provide insight into how white matter is changing in conditions such as schizophrenia, autism, depression, suicide, ADHD and PTSD,” she said.
The hippocampus regulates memory and emotions, and plays a role in various emotional disorders.
Kaufer and her colleagues published their findings in the Feb. 11 issue of the journal Molecular Psychiatry.
Does stress affect brain connectivity?
Kaufer’s findings suggest a mechanism that may explain some changes in brain connectivity in people with PTSD, for example. One can imagine, she said, that PTSD patients could develop a stronger connectivity between the hippocampus and the amygdala – the seat of the brain’s fight or flight response – and lower than normal connectivity between the hippocampus and prefrontal cortex, which moderates our responses.
“You can imagine that if your amygdala and hippocampus are better connected, that could mean that your fear responses are much quicker, which is something you see in stress survivors,” she said. “On the other hand, if your connections are not so good to the prefrontal cortex, your ability to shut down responses is impaired. So, when you are in a stressful situation, the inhibitory pathways from the prefrontal cortex telling you not to get stressed don’t work as well as the amygdala shouting to the hippocampus, ‘This is terrible!’ You have a much bigger response than you should.”
She is involved in a study to test this hypothesis in PTSD patients, and continues to study brain changes in rodents subjected to chronic stress or to adverse environments in early life.
Stress tweaks stem cells
Kaufer’s lab, which conducts research on the molecular and cellular effects of acute and chronic stress, focused in this study on neural stem cells in the hippocampus of the brains of adult rats. These stem cells were previously thought to mature only into neurons or a type of glial cell called an astrocyte. The researchers found, however, that chronic stress also made stem cells in the hippocampus mature into another type of glial cell called an oligodendrocyte, which produces the myelin that sheaths nerve cells.
The finding, which they demonstrated in rats and cultured rat brain cells, suggests a key role for oligodendrocytes in long-term and perhaps permanent changes in the brain that could set the stage for later mental problems. Oligodendrocytes also help form synapses – sites where one cell talks to another – and help control the growth pathway of axons, which make those synapse connections.
The fact that chronic stress also decreases the number of stem cells that mature into neurons could provide an explanation for how chronic stress also affects learning and memory, she said.
Kaufer is now conducting experiments to determine how stress in infancy affects the brain’s white matter, and whether chronic early-life stress decreases resilience later in life. She also is looking at the effects of therapies, ranging from exercise to antidepressant drugs, that reduce the impact of stress and stress hormones.
Vision is key to spatial skills
Try to conjure a mental image of your kitchen, or imagine the route that you take to work every day. For most people, this comes so naturally that we think nothing of it, but for neuroscientists, there is still much to learn about how the brain develops this critical skill, known as spatial imagery.
Sensory information from the eyes, ears, and sense of touch all contribute to our ability to imagine spatial structures, but questions remain about the influence of each sensory system. A new study from MIT neuroscientists suggests that visual input plays a special role in developing these skills, particularly for more complex tasks.
By studying children in India who were born blind but whose blindness could be treated, the researchers found that the children’s ability to perform more complex spatial imagery tasks improved markedly following surgery that restored their sight.
“Just four months of vision seems to have a significant impact on spatial imagery skills,” says Pawan Sinha, an MIT professor of brain and cognitive sciences and senior author of the paper. “That seems to be consistent with the greater richness of spatial information that vision provides. With audition and touch we get a coarser sense of the environment. With vision we have a much more fine-grained appreciation of the environment.”
The study, which appeared in a recent issue of the journal Psychological Science, grew out of Project Prakash, a charitable effort Sinha launched to identify and treat children in India suffering from curable forms of blindness, such as cataracts or corneal scarring.
Tapan Gandhi, a postdoc in Sinha’s lab, is the paper’s lead author; Suma Ganesh, an ophthalmologist at Dr. Shroff’s Charity Eye Hospital in New Delhi, is also an author.
How Your Memory Rewrites the Past
Your memory is a wily time traveler, plucking fragments of the present and inserting them into the past, reports a new Northwestern Medicine® study. In terms of accuracy, it’s no video camera.
Rather, the memory rewrites the past with current information, updating your recollections with new experiences.
Love at first sight, for example, is more likely a trick of your memory than a Hollywood-worthy moment.
“When you think back to when you met your current partner, you may recall this feeling of love and euphoria,” said lead author Donna Jo Bridge, a postdoctoral fellow in medical social sciences at Northwestern University Feinberg School of Medicine. “But you may be projecting your current feelings back to the original encounter with this person.”
The study is published Feb. 5 in the Journal of Neuroscience.
This the first study to show specifically how memory is faulty, and how it can insert things from the present into memories of the past when those memories are retrieved. The study shows the exact point in time when that incorrectly recalled information gets implanted into an existing memory.
To help us survive, Bridge said, our memories adapt to an ever-changing environment and help us deal with what’s important now.
“Our memory is not like a video camera,” Bridge said. “Your memory reframes and edits events to create a story to fit your current world. It’s built to be current.”
All that editing happens in the hippocampus, the new study found. The hippocampus, in this function, is the memory’s equivalent of a film editor and special effects team.
For the experiment, 17 men and women studied 168 object locations on a computer screen with varied backgrounds such as an underwater ocean scene or an aerial view of Midwest farmland. Next, researchers asked participants to try to place the object in the original location but on a new background screen. Participants would always place the objects in an incorrect location.
For the final part of the study, participants were shown the object in three locations on the original screen and asked to choose the correct location. Their choices were: the location they originally saw the object, the location they placed it in part 2 or a brand new location.
“People always chose the location they picked in part 2,” Bridge said. “This shows their original memory of the location has changed to reflect the location they recalled on the new background screen. Their memory has updated the information by inserting the new information into the old memory.”
Participants took the test in an MRI scanner so scientists could observe their brain activity. Scientists also tracked participants’ eye movements, which sometimes were more revealing about the content of their memories – and if there was conflict in their choices — than the actual location they ended up choosing.
The notion of a perfect memory is a myth, said Joel Voss, senior author of the paper and an assistant professor of medical social sciences and of neurology at Feinberg.
“Everyone likes to think of memory as this thing that lets us vividly remember our childhoods or what we did last week,” Voss said. “But memory is designed to help us make good decisions in the moment and, therefore, memory has to stay up-to-date. The information that is relevant right now can overwrite what was there to begin with.”
Bridge noted the study’s implications for eyewitness court testimony. “Our memory is built to change, not regurgitate facts, so we are not very reliable witnesses,” she said.
A caveat of the research is that it was done in a controlled experimental setting and shows how memories changed within the experiment. “Although this occurred in a laboratory setting, it’s reasonable to think the memory behaves like this in the real world,” Bridge said.
(Source: northwestern.edu)
Brain Scans Show We Take Risks Because We Can’t Stop Ourselves
A new study correlating brain activity with how people make decisions suggests that when individuals engage in risky behavior, such as drunk driving or unsafe sex, it’s probably not because their brains’ desire systems are too active, but because their self-control systems are not active enough.
This might have implications for how health experts treat mental illness and addiction or how the legal system assesses a criminal’s likelihood of committing another crime.
Researchers from The University of Texas at Austin, UCLA and elsewhere analyzed data from 108 subjects who sat in a magnetic resonance imaging (MRI) scanner — a machine that allows researchers to pinpoint brain activity in vivid, three-dimensional images — while playing a video game that simulates risk-taking.
The researchers used specialized software to look for patterns of activity across the whole brain that preceded a person’s making a risky choice or a safe choice in one set of subjects. Then they asked the software to predict what other subjects would choose during the game based solely on their brain activity. The software accurately predicted people’s choices 71 percent of the time.
“These patterns are reliable enough that not only can we predict what will happen in an additional test on the same person, but on people we haven’t seen before,” said Russell Poldrack, director of UT Austin’s Imaging Research Center and professor of psychology and neuroscience.
When the researchers trained their software on much smaller regions of the brain, they found that just analyzing the regions typically involved in executive functions such as control, working memory and attention was enough to predict a person’s future choices. Therefore, the researchers concluded, when we make risky choices, it is primarily because of the failure of our control systems to stop us.
“We all have these desires, but whether we act on them is a function of control,” said Sarah Helfinstein, a postdoctoral researcher at UT Austin and lead author of the study that appears online this week in the journal Proceedings of the National Academy of Sciences.
Helfinstein said that additional research could focus on how external factors, such as peer pressure, lack of sleep or hunger, weaken the activity of our brains’ control systems when we contemplate risky decisions.
“If we can figure out the factors in the world that influence the brain, we can draw conclusions about what actions are best at helping people resist risks,” said Helfinstein.
To simulate features of real-world risk-taking, the researchers used a video game called the Balloon Analogue Risk Task (BART) that past research has shown correlates well with self-reported risk-taking such as drug and alcohol use, smoking, gambling, driving without a seatbelt, stealing and engaging in unprotected sex.
While playing the BART, the subject sees a balloon on the screen and is asked to make either a risky choice (inflate the balloon a little and earn a few cents) or a safe choice (stop the round and “cash out,” keeping whatever money was earned up to that point). Sometimes inflating the balloon causes it to burst and the player loses all the cash earned from that round. After each successful balloon inflation, the game continues with the chance of earning another standard-sized reward or losing an increasingly large amount. Many health-relevant risky decisions share this same structure, such as when deciding how many alcoholic beverages to drink before driving home or how much one can experiment with drugs or cigarettes before developing an addiction.
The data for this study came from the Consortium for Neuropsychiatric Phenomics at UCLA, which recruited adults from the Los Angeles area for researchers to examine differences in response inhibition and working memory between healthy adults and patients diagnosed with bipolar disorder, schizophrenia, or adult attention deficit hyperactivity disorder (ADHD). Only data collected from healthy participants were included in the present analyses.
A shock to the system: Electroconvulsive Therapy shows mood disorder-specific therapeutic benefits
The oldest well-established procedure for somatic treatment of unipolar and bipolar disorders, electroconvulsive therapy (ECT) has, at best, a variegated reputation – and not just in its reputation for being a “barbaric” treatment modality (which, as it turns out, it is not). The scientific, clinical, and ethical controversy extends to unanswered questions about its precise mechanism of action – that is, how major electrical discharge over half the brain shows efficacy in recovery from a range of sometimes quite distinct psychological and psychiatric disorders. Recently, however, scientists at Université de Lausanne, Lausanne, Switzerland and Charité University Medicine, Berlin, Germany found local but not general anatomical brain changes following electroconvulsive therapy that are differently distributed in each disease, and are actually the areas believed to be abnormal in each disorder. Since interaction between ECT and specific pathology appears to be therapeutically causal, the researchers state that their results have implications for deep brain stimulation, transcranial magnetic stimulation and other electrically-based brain treatments.
Prof. Bogdan Draganski discussed the paper that he, Dr. Juergen Dukart and their co-authors published in Proceedings of the National Academy of Sciences.