Posts tagged fMRI
Articles and news from the latest research reports.
Neuroscientists Investigate Lotteries to Study How the Brain Evaluates Risk
People are faced with thousands of choices every day, some inane and some risky. Scientists know that the areas of the brain that evaluate risk are the same for each person, but what makes the value assigned to risk different for individuals?
To answer this question, a new video article in Journal of Visualized Experiments (JoVE) uses functional magnetic resonance imaging (fMRI) to characterize subjective risk assessment while subjects choose between different lotteries to play.
The article, a joint effort from laboratories at Yale School of Medicine and New York University, is led by Yale’s Dr. Ifat Levy. Dr. Levy explains, “This procedure allows us to examine all kinds of normal and pathological behaviors focusing on risk assessment. It could explain things like substance abuse and over-eating from a different perspective than how it is usually characterized.”
I’ve been up since 6 am. I’ve had a breath test for alcohol, a urine test for drugs and a psychological test for mental health. Then I’m handed a red pill and a glass of water. I swallow it… and I’m told to relax. Which is easier said than done when you don’t know if you’ve just taken vitamin C or 83 milligrams of pure MDMA.
I’m taking part in a groundbreaking study on MDMA, the drug commonly known as ecstasy. The research is run by David Nutt of Imperial College London, a former government adviser and one of the few UK researchers licensed to study class-A drugs.
His main aim is to discover what MDMA does to the human brain, something that, remarkably, has never been done before. A second goal is to study MDMA as a therapy for post-traumatic stress disorder. The experiment is also being filmed for a Channel 4 documentary called Drugs Live: The Ecstasy Trial, which will be broadcast in the UK next week.
Imaging the network traffic in our brains
MRI brain scans no longer just show the various regions of brain activity; nowadays the networks in the brain can now be imaged with ever greater precision. This will make functional MRI (fMRI) increasingly powerful in the coming years, leading to tools that can be used in cognitive neuroscience. This is the claim made by Prof. David Norris in his inaugural lecture as Professor of Neuroimaging at the University of Twente on 13 September.
During the twenty years since the invention of fMRI (functional Magnetic Resonance Imaging) developments have come thick and fast, from initially identifying active brain regions to more complex analysis of the connections and hubs in the brain. In his inaugural lecture Norris describes how this has been achieved thanks to not only a growing understanding of the underlying biophysics but also rapid technological developments: scanners with larger magnetic fields, better image-processing techniques and algorithms. His aim is to go beyond merely localizing which parts of the brain are active. The challenge is to answer two questions: How are the various regions interconnected, structurally and functionally? What do the networks in our brains look like?
Faster and more powerful
Back in the 19th century scientists observed increased blood flow in brain regions that are functionally active. fMRI enables the change in oxygen content to be seen. Haemoglobin, the substance that transports oxygen in the blood, can take the form of oxyhaemoglobin (when it is still combined with oxygen) and deoxyhaemoglobin (when the oxygen has been released), each of which has different magnetic properties. One of the complicating factors when interpreting the scans is that various physiological mechanisms are at work simultaneously, causing the deoxyhaemoglobin level to rise and fall. One of the remedies to increase accuracy, Norris explains, has been to increase the magnetic field strength: there are now MRI scanners operating at 7 Tesla. At the same time the speed at which laminae can be imaged has gone up by leaps and bounds: the entire brain can be scanned in three seconds with a precision of 1 millimetre.
Hubs
The functional connections between parts of the brain can be registered by means of blood flow, but MRI also enables the structural and anatomical connections to be seen. This involves measuring the movement of water molecules caused by the ‘white matter’ in nerve fibres. This technology is known as diffusion-weighted imaging (DWI). Combining these technologies provides a wealth of fresh information on the networks in the brain and the places where many connections come together, the ‘hubs’. Not only have ‘known networks’ thus been proven, so have networks that neuroscience posits as plausible but that have never been measured.
Image showing the distribution of connector hubs on the surface of a flattened brain. The top two figures show the medial views of each hemisphere, the bottom two show the external views.
CMI
The new Centre for Medical Imaging that is to come to the University of Twente campus will soon provide extensive facilities for collaborating in the field of fMRI, says Norris, who is also on the staff of the Donders Institute in Nijmegen.
(Source: utwente.nl)
You already know it’s hard to balance your checkbook while simultaneously reflecting on your past. Now, investigators at the Stanford University School of Medicine — having done the equivalent of wire-tapping a hard-to-reach region of the brain — can tell us how this impasse arises.
The researchers showed that groups of nerve cells in a structure called the posterior medial cortex, or PMC, are strongly activated during a recall task such as trying to remember whether you had coffee yesterday, but just as strongly suppressed when you’re engaged in solving a math problem.
The PMC, situated roughly where the brain’s two hemispheres meet, is of great interest to neuroscientists because of its central role in introspective activities.
“This brain region is famously well-connected with many other regions that are important for higher cognitive functions,” said Josef Parvizi, MD, PhD, associate professor of neurology and neurological sciences and director of Stanford’s Human Intracranial Cognitive Electrophysiology Program. “But it’s very hard to reach. It’s so deep in the brain that the most commonly used electrophysiological methods can’t access it.”
Ιn a study published online Sept. 3 in Proceedings of the National Academy of Sciences, Parvizi and his Stanford colleagues found a way to directly and sensitively record the output from this ordinarily anatomically inaccessible site in human subjects. By doing so, the researchers learned that particular clusters of nerve cells in the PMC that are most active when you are recalling details of your own past are strongly suppressed when you are performing mathematical calculations.
Stimulating the brain through touch
July 19, 2012
(Medical Xpress) — When learning to master complex movements such as those required in surgery, is being physically guided by an expert more effective than learning through trial and error?
Dr. George Van Doorn and a participant in the fMRI
New research by Monash University’s Departments of Psychological Studies and Physiology challenges earlier claims that externally guided (or passive) movement is a superior learning method to self-generated (or active) movement.
In the first study of its kind, researchers discovered that different brain regions become active depending on the type of movement used. Lead researcher Dr. George Van Doorn, head of Psychological Studies, said the findings did not support the view that passive movement was a more effective way to learn.
“There has been much debate over the last 30 years about which form of movement is better,” Dr. Van Doorn said. “We found that active movements result in greater activation in brain areas implicated in higher-order processes such as monitoring and controlling goal-directed behaviour, attention, execution of movements, and error detection.
“Passive movements, in contrast, produced greater activity in areas associated with touch perception, length discrimination, tactile object recognition, and the attenuation of sensory inputs.”
People were tested while making movements themselves, and while being guided.
“Whilst inside a functional Magnetic Resonance Imaging (fMRI) machine, we had people either freely move their index finger around a two-dimensional, raised-line pattern to measure self-generated touch. Or we had an experimenter guide the person’s finger around the pattern, to measure externally generated touch. Using the fMRI, we found that different brain regions become active depending on the type of movement used,” Dr. Van Doorn said.
Dr. Van Doorn said touch was becoming a popular area of investigation, with more scientists contributing to understanding about this important, though under-acknowledged, sensory system.
All researchers involved in this study are located at Monash University’s Gippsland campus. The study findings were presented at EuroHaptics 2012, a major international conference and the primary European meeting for researchers in the field of human haptic sensing and touch-enabled computer applications.
Provided by Monash University
Source: medicalxpress.com
Brain scanner, not joystick, is in human-robot future
July 6, 2012 by Nancy Owano
(Phys.org) — Talk about fMRI may not be entirely familiar to many people, but that could change with new events that are highlighting efforts to link up humans and machines. fMRI (Functional Magnetic Resonance Imaging) is a promising technology that can help human move beyond joysticks to control robots via brain scanners instead. Now a research project exploring ways to develop robot surrogates with whom humans can interact has turned a corner. A university student‘s ability to make his robot surrogate move around, using fMRI technology, was successful. The experiment linked up Israeli student Tirosh Shapira in a lab at Bar-Ilan University, Israel, with a small robot in another lab far away at Beziers Technology Institute in France.
Shapira merely had to think about moving his arms or legs and the robot, with a camera on its head with an image displayed in front of Shapira, successfully would do the same. If Shapira thought about moving forward or backward, the robot responded accordingly.
fmri monitors blood flowing through the brain and can spot when areas associated with certain actions, such as movement, are in use. The fMRI read the student’s thoughts, which were translated via computer into commands relayed across the Internet to the robot in France.
There is much more work to be done to advance this approach, however. The researchers seek to devise a different type of scanning. An fMRI scanner is an expensive piece of equipment but the scientists believe that improvements in software might allow for a head-mounted device. Another research goal is to see if they can get humans to speak via the robot. The size of the robot will need modification, closer to the size and movement of a human, and engineered with a wider range of movement that would include hand gestures. In sum, according to the researchers, this experiment is only one of many steps ahead.
Medical applications for this technology are seen as promising, especially as scientists explore how patients with paralysis can interface with robots so that the patients can reconnect to the world. Another suggested application has been in the military, where robot surrogates rather than soldiers would be sent into battle.
Source: PHYS.ORG
Your brain on ‘shrooms: fMRI elucidates neural correlates of psilocybin psychedelic state
Decreased cerebral blood flow (CBF) after psilocybin imaged by fMRI. Regions where there was significantly decreased CBF after psilocybin versus after placebo are shown in blue. No CBF increases in any region were observed. Image Copyright © PNAS, doi:10.1073/pnas.1119598109
(Medical Xpress) — Psychedelic substances have long been used for healing, ceremonial, or mind-altering subjective experiences due to compounds that, when ingested or inhaled, generate hallucinations, perceptual distortions, or altered states of awareness. Of these, the psychedelic substance psilocybin, the prodrug (a precursor of a drug that must in vivo chemical conversion by metabolic processes before becoming an active pharmacological agent) of psilocin (4-hydroxy-dimethyltryptamine) and the key hallucinogen found in so-called magic mushrooms, is widely used not only in healing ceremonies, but, more recently, in psychotherapy as well – but little has been known about its specific activity in the brain.
Recently, however, scientists in the Neuropsychopharmacology Unit at Imperial College London used complementary blood-oxygen level dependent (BOLD) functional MRI, or fMRI, in conjunction with a technique for imaging the transition from normal waking consciousness to the psychedelic state. The study found decreased blood flow and BOLD in the thalamus, anterior and posterior cingulate cortex, and medial prefrontal cortex. The researchers concluded that the surprising results strongly suggest that the subjective effects of psychedelic drugs are caused by decreased activity and connectivity in the brain’s key connector hubs, enabling a state of unconstrained cognition.
Lead researcher Dr. Robin L. Carhart-Harris, working in the Neuropsychopharmacology Unit created by Prof. David J. Nutt, recounts the team’s main challenges in establishing an fMRI methodology that would be specific enough to highly correlate neurophysiological activity with the neuronal presence or absence of psilocybin. “There were a number of considerations,” Carhart-Harris tells Medical Xpress. “In terms of experimental design, we had to determine the precise dose and delivery protocol that would be appropriate for obtaining clear fMRI results. “For example,” he explains, “we had to consider temporal dynamics: If the drug was administered orally, the protracted period of time between ingestion, metabolism, and crossing of the blood-brain barrier would fall outside of the short scanning window needed to capture induced brain activity.” They therefore had to rely on intravenous administration.
The Love Competition from Brent Hoff on Vimeo.
Is it possible for one person to love more than another? In an attempt to find out, filmmaker Brent Hoff teamed with Stanford University neuroscientists to test lovers’ abilities, using an fMRI to monitor brain activity and measure whose adoration was the strongest.