Posts tagged neuroimaging
Articles and news from the latest research reports.
Mapping brain circuitry
Common psychiatric disorders, such as anxiety and addiction, likely result from changes in brain circuitry. Understanding structural and functional brain connections – and how they change in psychiatric disorders – could lead to novel preventive and therapeutic strategies.
The bed nucleus of the stria terminalis (BNST) has been linked to both anxiety and addiction, but its circuitry in humans has not been described. Jennifer Blackford, Ph.D., assistant professor of Psychiatry, and colleagues used two neuroimaging methods – diffusion tensor imaging and functional MRI – to identify patterns of connectivity between the BNST and other brain regions in healthy individuals. The BNST showed connections to multiple subcortical brain regions, including limbic, thalamic and basal ganglia structures, which matched reported connections in rodents. The researchers also identified two novel BNST connections: to the temporal pole and to the paracingulate gyrus.
The findings, reported in NeuroImage, provide a map of BNST neurocircuitry and lay the foundation for future studies of the circuits that mediate anxiety and addiction.
(Source: news.vanderbilt.edu)
New Guidance System Could Improve Minimally Invasive Surgery
Johns Hopkins researchers have devised a computerized process that could make minimally invasive surgery more accurate and streamlined using equipment already common in the operating room.
In a report published recently in the journal Physics in Medicine and Biology, the researchers say initial testing of the algorithm shows that their image-based guidance system is potentially superior to conventional tracking systems that have been the mainstay of surgical navigation over the last decade.
“Imaging in the operating room opens new possibilities for patient safety and high-precision surgical guidance,” says Jeffrey Siewerdsen, Ph.D., a professor of biomedical engineering in the Johns Hopkins University School of Medicine. “In this work, we devised an imaging method that could overcome traditional barriers in precision and workflow. Rather than adding complicated tracking systems and special markers to the already busy surgical scene, we realized a method in which the imaging system is the tracker and the patient is the marker.”
Yale researchers reconstruct facial images locked in a viewer’s mind
Using only data from an fMRI scan, researchers led by a Yale University undergraduate have accurately reconstructed images of human faces as viewed by other people.
“It is a form of mind reading,” said Marvin Chun, professor of psychology, cognitive science and neurobiology and an author of the paper in the journal Neuroimage.
The increased level of sophistication of fMRI scans has already enabled scientists to use data from brain scans taken as individuals view scenes and predict whether a subject was, for instance, viewing a beach or city scene, an animal or a building.
“But they can only tell you they are viewing an animal or a building, not what animal or building,” Chun said. “This is a different level of sophistication.”
One of Chun’s students, Alan S. Cowen, then a Yale junior now pursing an advanced degree at the University of California at Berkeley, wanted to know whether it would be possible to reconstruct a human face from patterns of brain activity. The task was daunting, because faces are more similar to each other than buildings. Also large areas of the brain are recruited in the processing of human faces, a testament to its importance in survival.
“We perceive faces in a much greater level of detail than we perceive other things,” Cowen said.
Working with funding from the Yale Provost’s office, Cowen and post doctoral researcher Brice Kuhl, now an assistant professor at New York University, showed six subjects 300 different “training” faces while undergoing fMRI scans. They used the data to create a sort of statistical library of how those brains responded to individual faces. They then showed the six subjects new sets of faces while they were undergoing scans. Taking that fMRI data alone, researchers used their statistical library to reconstruct the faces their subjects were viewing.
Cowen said the accuracy of these facial reconstructions will increase with time and he envisions they can be used as a research tool, for instance in studying how autistic children respond to faces.
Chun said the study shows the value of funding research ambitions of Yale undergraduates.
“I would never have received external funding for this, it was too novel,” Chun said.
Overlapping Neural Systems Represent Cognitive Effort and Reward Anticipation
Anticipating a potential benefit and how difficult it will be to obtain it are valuable skills in a constantly changing environment. In the human brain, the anticipation of reward is encoded by the Anterior Cingulate Cortex (ACC) and Striatum. Naturally, potential rewards have an incentive quality, resulting in a motivational effect improving performance. Recently it has been proposed that an upcoming task requiring effort induces a similar anticipation mechanism as reward, relying on the same cortico-limbic network. However, this overlapping anticipatory activity for reward and effort has only been investigated in a perceptual task. Whether this generalizes to high-level cognitive tasks remains to be investigated. To this end, an fMRI experiment was designed to investigate anticipation of reward and effort in cognitive tasks. A mental arithmetic task was implemented, manipulating effort (difficulty), reward, and delay in reward delivery to control for temporal confounds. The goal was to test for the motivational effect induced by the expectation of bigger reward and higher effort. The results showed that the activation elicited by an upcoming difficult task overlapped with higher reward prospect in the ACC and in the striatum, thus highlighting a pivotal role of this circuit in sustaining motivated behavior.
The study, part-funded by the Medical Research Council (MRC) and published online in PNAS, challenges the idea that suppressed memories remain fully preserved in the brain’s unconscious, allowing them to be inadvertently expressed in someone’s behaviour. The results of the study suggest instead that the act of suppressing intrusive memories helps to disrupt traces of the memories in the parts of the brain responsible for sensory processing.
The team at the MRC Cognition and Brain Sciences Unit and the University of Cambridge’s Behavioural and Clinical Neuroscience Institute (BCNI) have examined how suppression affects a memory’s unconscious influences in an experiment that focused on suppression of visual memories, as intrusive unwanted memories are often visual in nature.
After a trauma, most people report intrusive memories or images, and people will often try to push these intrusions from their mind, as a way to cope. Importantly, the frequency of intrusive memories decreases over time for most people. It is critical to understand how the healthy brain reduces these intrusions and prevents unwanted images from entering consciousness, so that researchers can better understand how these mechanisms may go awry in conditions such as post-traumatic stress disorder.
Participants were asked to learn a set of word-picture pairs so that, when presented with the word as a reminder, an image of the object would spring to mind. After learning these pairs, brain activity was recorded using functional magnetic resonance imaging (fMRI) while participants either thought of the object image when given its reminder word, or instead tried to stop the memory of the picture from entering their mind.
The researchers studied whether suppressing visual memories had altered people’s ability to see the content of those memories when they re-encountered it again in their visual worlds. Without asking participants to consciously remember, they simply asked people to identify very briefly displayed objects that were made difficult to see by visual distortion. In general, under these conditions, people are better at identifying objects they have seen recently, even if they do not remember seeing the object before—an unconscious influence of memory. Strikingly, they found that suppressing visual memories made it harder for people to later see the suppressed object compared to other recently seen objects.
Brain imaging showed that people’s difficulty seeing the suppressed object arose because suppressing the memory from conscious awareness in the earlier memory suppression phase had inhibited activity in visual areas of the brain, disrupting visual memories that usually help people to see better. In essence, suppressing something from the mind’s eye had made it harder to see in the world, because visual memories and seeing rely on the same brain areas: out of mind, out of sight.
Over the last decade, research has shown that suppressing unwanted memories reduces people’s ability to consciously remember the experiences. The researchers’ studies on memory suppression have been inspired, in part, by trying to understand how people adapt memory after psychological trauma. Although this may work as a coping mechanism to help people adapt to the trauma, there is the possibility that if the memory traces were able to exert an influence on unconscious behaviour, they could potentially exacerbate mental health problems. The idea that suppression leaves unconscious memories that undermine mental health has been influential for over a century, beginning with Sigmund Freud.
These findings challenge the assumption that, even when supressed, a memory remains fully intact, which can then be expressed unconsciously. Moreover, this discovery pinpoints the neurobiological mechanisms underlying how this suppression process happens, and could inform further research on uncontrolled ‘intrusive memories’, a classic characteristic of post-traumatic stress disorder.
Dr Michael Anderson, at the MRC Cognition and Brain Sciences Unit said: “While there has been a lot of research looking at how suppression affects conscious memory, few studies have examined the influence this process might have on unconscious expressions of memory in behaviour and thought. Surprisingly, the effects of suppression are not limited to conscious memory. Indeed, it is now clear, that the influence of suppression extends beyond areas of the brain associated with conscious memory, affecting perceptual traces that can influence us unconsciously. This may contribute to making unwanted visual memories less intrusive over time, and perhaps less vivid and detailed.”
Dr Pierre Gagnepain, lead author at INSERM in France said: “Our memories can be slippery and hard to pin down. Out of hand and uncontrolled, their remembrance can haunt us and cause psychological troubles, as we see in PTSD. We were interested whether the brain can genuinely suppress memories in healthy participants, even at the most unconscious level, and how it might achieve this. The answer is that it can, though not all people were equally good at this. The better understanding of the neural mechanisms underlying this process arising from this study may help to better explain differences in how well people adapt to intrusive memories after a trauma”
Researchers identify decision-making center of brain
Although choosing to do something because the perceived benefit outweighs the financial cost is something people do daily, little is known about what happens in the brain when a person makes these kinds of decisions. Studying how these cost-benefit decisions are made when choosing to consume alcohol, University of Georgia associate professor of psychology James MacKillop identified distinct profiles of brain activity that are present when making these decisions.
"We were interested in understanding how the brain makes decisions about drinking alcohol. Particularly, we wanted to clarify how the brain weighs the pros and cons of drinking," said MacKillop, who directs the Experimental and Clinical Psychopharmacology Laboratory in the UGA Franklin College of Arts and Sciences.
The study combined functional magnetic resonance imaging and a bar laboratory alcohol procedure to see how the cost of alcohol affected people’s preferences. The study group included 24 men, age 21-31, who were heavy drinkers. Participants were given a $15 bar tab and then were asked to make decisions in the fMRI scanner about how many drinks they would choose at varying prices, from very low to very high. Their choices translated into real drinks, at most eight that they received in the bar immediately after the scan. Any money not spent on drinks was theirs to keep.
The study applied a neuroeconomic approach, which integrates concepts and methods from psychology, economics and cognitive neuroscience to understand how the brain makes decisions. In this study, participants’ cost-benefit decisions were categorized into those in which drinking was perceived to have all benefit and no cost, to have both benefits and costs, and to have all costs and no benefits. In doing so, MacKillop could dissect the neural mechanisms responsible for different types of cost-benefit decision-making.
"We tried to span several levels of analysis, to think about clinical questions, like why do people choose to drink or not drink alcohol, and then unpack those choices into the underlying units of the brain that are involved," he said.
When participants decided to drink in general, activation was seen in several areas of the cerebral cortex, such as the prefrontal and parietal cortices. However, when the decision to drink was affected by the cost of alcohol, activation involved frontostriatal regions, which are important for the interplay between deliberation and reward value, suggesting suppression resulting from greater cognitive load. This is the first study of its kind to examine cost-benefit decision-making for alcohol and was the first to apply a framework from economics, called demand curve analysis, to understanding cost-benefit decision making.
"The brain activity was most differentially active during the suppressed consumption choices, suggesting that participants were experiencing the most conflict," MacKillop said. "We had speculated during the design of the study that the choices not to drink at all might require the most cognitive effort, but that didn’t seem to be the case. Once people decided that the cost of drinking was too high, they didn’t appear to experience a great deal of conflict in terms of the associated brain activity."
These conflicted decisions appeared to be represented by activity in the anterior insula, which has been linked in previous addiction studies to the motivational circuitry of the brain. Not only encoding how much people crave or value drugs, this portion of the brain is believed to be responsible for processing interceptive experiences, a person’s visceral physiological responses.
"It was interesting that the insula was sensitive to escalating alcohol costs especially when the costs of drinking outweighed the benefits," MacKillop said. "That means this could be the region of the brain at the intersection of how our rational and irrational systems work with one another. In general, we saw the choices associated with differential brain activity were those choices in the middle, where people were making choices that reflect the ambivalence between cost and benefits. Where we saw that tension, we saw the most brain activity."
While MacKillop acknowledges the impact this research could have on neuromarketing-or understanding how the brain makes decisions about what to buy-he is more interested in how this research can help people with alcohol addictions.
"These findings reveal the distinct neural signatures associated with different kinds of consumption preferences. Now that we have established a way of studying these choices, we can apply this approach to better understanding substance use disorders and improving treatment," he said, adding that comparing fMRI scans from alcoholics with those of people with normal drinking habits could potentially tease out brain patterns that show what is different between healthy and unhealthy drinkers. "In the past, we have found that behavioral indices of alcohol value predict poor treatment prognosis, but this would permit us to understand the neural basis for negative outcomes."
The research was published in the journal Neuropsychopharmacology March 3. A podcast highlighting this work is available at http://www.nature.com/multimedia/podcast/npp/npp_030314_alcohol.mp3.
Nicotine Withdrawal Weakens Brain Connections Tied to Self-Control Over Cigarette Cravings
People who try to quit smoking often say that kicking the habit makes the voice inside telling them to light up even louder, but why people succumb to those cravings so often has never been fully understood. Now, a new brain imaging study in this week’s JAMA Psychiatry from scientists in Penn Medicine and the National Institute on Drug Abuse (NIDA) Intramural Research Program shows how smokers suffering from nicotine withdrawal may have more trouble shifting from a key brain network—known as default mode, when people are in a so-called “introspective” or “self-referential” state— and into a control network, the so-called executive control network, that could help exert more conscious, self-control over cravings and to focus on quitting for good.
The findings help validate a neurobiological basis behind why so many people trying to quit end up relapsing—up to 80 percent, depending on the type of treatment—and may lead to new ways to identify smokers at high risk for relapse who need more intensive smoking cessation therapy.
The brain imaging study was led by researchers at University of Pennsylvania’s new Brain and Behavior Change Program, led by Caryn Lerman, PhD, who is also the deputy director of Penn’s Abramson Cancer Center, and Elliot Stein, PhD, and collaborators at NIDA. They found that smokers who abstained from cigarettes showed weakened interconnectivity between certain large-scale networks in their brains: the default mode network, the executive control network, and the salience network. They posit that this weakened connectivity reduces smokers’ ability to shift into or maintain greater influence from the executive control network, which may ultimately help maintain their quitting attempt.
“What we believe this means is that smokers who just quit have a more difficult time shifting gears from inward thoughts about how they feel to an outward focus on the tasks at hand,” said Lerman, who also serves as the Mary W. Calkins professor in the Department of Psychiatry. “It’s very important for people who are trying to quit to be able to maintain activity within the control network— to be able to shift from thinking about yourself and your inner state to focus on your more immediate goals and plan.”
Prior studies have looked at the effects of nicotine on brain interconnectivity in the resting state, that is, in the absence of any specific goal directed activity. This is the first study, however, to compare resting brain connectivity in an abstinent state and when people are smoking as usual, and then relate those changes to symptoms of craving and mental performance.
For the study, researchers conducted brain scans on 37 healthy smokers (those who smoke more than 10 cigarettes a day) ages 19 to 61 using functional magnetic resonance imaging (fMRI) in two different sessions: 24 hours after biochemically confirmed abstinence and after smoking as usual.
Imaging showed a significantly weaker connectivity between the salience network and default mode network during abstinence, compared with their sated state. Also, weakened connectivity during abstinence was linked with increases in smoking urges, negative mood, and withdrawal symptoms, suggesting that this weaker internetwork connectivity may make it more difficult for people to quit.
Establishing the strength of the connectivity between these large-scale brain networks will be important in predicting people’s ability to quit and stay quit, the authors write. Also, such connectivity could serve as a clinical biomarker to identify smokers who are most likely to respond to a particular treatment.
“Symptoms of withdrawal are related to changes in smokers’ brains, as they adjust to being off of nicotine, and this study validates those experiences as having a biological basis,” said Lerman. “The next step will be to identify in advance those smokers who will have more difficultly quitting and target more intensive treatments, based on brain activity and network connectivity.”
(Source: uphs.upenn.edu)
Outside the body our memories fail us
New research from Karolinska Institutet and Umeå University in Sweden demonstrates for the first time that there is a close relationship between body perception and the ability to remember. For us to be able to store new memories from our lives, we need to feel that we are in our own body. According to researchers, the results could be of major importance in understanding the memory problems that psychiatric patients often exhibit.
The memories of what happened on the first day of school are an example of an episodic memory. How these memories are created and how the role that the perception of one’s own body has when storing memories has long been inconclusive. Swedish researchers can now demonstrate that volunteers who experience an exciting event whilst perceiving an illusion of being outside their own body exhibit a form of memory loss.
“It is already evident that people who have suffered psychiatric conditions in which they felt that they were not in their own body have fragmentary memories of what actually occurred”, says Loretxu Bergouignan, principal author of the current study. “We wanted to see how this manifests itself in healthy subjects.”
The study, which is published in the scientific journal PNAS, involved a total of 84 students reading about and undergoing four oral questioning sessions. To make these sessions extra memorable, an actor (Peter Bergared) took up the role of examiner – a (fictional) very eccentric professor at Karolinska Institutet. Two of the interrogations were perceived from a first person perspective from their own bodies in the usual way, while the participants in the other two sessions experienced a created illusion of being outside their own body. In both cases, the participants wore virtual reality goggles and earphones. One week later, they either underwent memory testing where they had to recall the events and provide details about what had happened, in which order, and what they felt, or they had to try to remember the events while they underwent brain imaging with functional magnetic resonance imaging (fMRI).
It then turned out that the participants remembered the ‘out-of-body’ interrogations significantly worse than those experienced from the normal ‘In body’ perspective. This was the case despite the fact that they responded equally well to the questions from each situation and also indicated that they experienced the same level of emotion. The fMRI scans further revealed a crucial difference in activity in the portion of the temporal lobe – the hippocampus – that is known to be central for episodic memories.
“When they tried to remember what happened during the interrogations experienced out-of-body, activity in the hippocampus was eliminated, unlike when they remembered the other situations. However, we could see activity in the frontal lobe cortex, so they were really making an effort to remember”, says professor Henrik Ehrsson, the research group leader behind the study.
The researchers’ interpretation of the results is that there is a close relationship between body experience and memory. Our brain constantly creates the experience of one’s own body in space by combining information from multiple senses: sight, hearing, touch, and more. When a memory is created, it is the task of the hippocampus to link all the information found in the cerebral cortex into a unified memory for further long-term storage. During the experience of being outside one’s body, this memory storage process is disturbed, whereupon the brain creates fragmentary memories instead.
“We believe that this new knowledge may be important for future research on memory disorders in a number of psychiatric conditions such as post-traumatic stress disorder, borderline personality disorder and certain psychoses where patients have dissociative experiences,” says Loretxu Bergouignan.
(Source: news.cision.com)
Inherited Alzheimer’s damage greater decades before symptoms appear
In a paper published in the prestigious journal Science Translational Medicine, Professor Colin Masters from the Florey Institute of Neuroscience and Mental Health and University of Melbourne – and colleagues in the UK and US – have found rapid neuronal damage begins 10 to 20 years before symptoms appear.
“As part of this research we have observed other changes in the brain that occur when symptoms begin to appear. There is actually a slowing of the neurodegeneration,” said Professor Masters.
Autosomal-dominant Alzheimer’s affects families with a genetic mutation, predisposing them to the crippling disease. These families provide crucial insight into the development of Alzheimer’s because they can be identified years before symptoms develop. The information gleaned from this group will also influence treatment offered to those living with the more common age-related version. Only about one per cent of those with Alzheimer’s have the genetic type of the disease.
The next part of the study involves a clinical trial. Using a range of imaging techniques (MRI and PET) and analysis of blood and cerebrospinal fluid, individuals from the US, UK and Australia will be observed as they trial new drugs to test their safety, side effects and changes within the brain.
“As part of an international study, family members are invited to be part of a trial in which two experimental drugs are offered many years before symptoms appear,” Prof Masters says. “It’s going to be very interesting to see how clinical intervention affects this group of patients in the decades before symptoms appear.”
The Florey is looking to recruit more participants in the Dominantly Inherited Alzheimer Network (DIAN) study. Those who either know they have a genetic mutation that causes autosomal-dominant Alzheimer’s or who don’t know their genetic status but have a parent or sibling with the mutation are invited to email: dian@florey.edu.au
Researchers Use Computers to “See” Neurons to Better Understand Brain Function
A study conducted by local high school students and faculty from the Department of Computer and Information Science in the School of Science at Indiana University-Purdue University Indianapolis reveals new information about the motor circuits of the brain that may one day help those developing therapies to treat conditions such as stroke, schizophrenia, spinal cord injury or Alzheimer’s disease.
"MRI and CAT scans of the human brain can tell us many things about the structure of this most complicated of organs, formed of trillions of neurons and the synapses via which they communicate. But we are a long way away from having imaging techniques that can show single neurons in a complex brain like the human brain," said Gavriil Tsechpenakis, Ph.D., assistant professor of computer science in the School of Science at IUPUI.
"But using the tools of artificial intelligence, specifically computer vision and image processing, we are able to visualize and process actual neurons of model organisms. Our work in the brain of a model organism—the fruit fly—will help us and other researchers move forward to more complex organisms with the ultimate goal of reconstructing the human central nervous system to gain insight into what goes wrong at the cellular level when devastating disorders of the brain and spinal cord occur. This understanding may ultimately inform the treatment of these conditions," said Tsechpenakis.
In this study, which processed images and reconstructed neuronal motor circuitry in the brain, the researchers, who included two Indianapolis high school students—Rachel Stephens and Tiange (Tony) Qu—collected and analyzed data on minute structures over various developmental stages, efforts linking neuroscience and computer science.
"Both high school students who worked on this study performed neuroscience and computation efforts similar to that conducted elsewhere by graduate students. It was impressive to see what sophisticated and key work they could—with mentoring—do," said Tsechpenakis.
Qu said the work was initially rather scary and intimidating but that he rapidly grew to appreciate the opportunity to work in the School of Science lab. “Unlike high school, we were not told how to get from point A to point B. Dr. Tsechpenakis explained what point A and B were and taught us how to figure out how to get from A to B.”
Qu, a 17-year-old senior at Ben Davis High School, now sees neuroscience as a potential college major with biomedical research as an eventual career goal. He continues to work in the lab after school focusing on change over time in fruit fly larvae motor neurons.
Stephens, a senior at North Central High School, said she enjoyed the collaborative nature of the research, with computer scientists and life scientists working together on a problem.
"Dr. Tsechpenakis made it clear to us that different perspectives are necessary, and the ability to think about a problem is more valuable than the education and training you’ve had,” she said. “Before I joined the lab I hadn’t really thought about how computer science could help heal." The 17-year-old plans a pre-med major in college and a career as a physician.