Posts tagged neuroimaging
Articles and news from the latest research reports.
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)
Memory vs. Math: Same brain areas show inverse responses to recall and arithmetic
Scientists have historically relied on neuroimaging – but not electrophysiological – data when studying the human default mode network (DMN), a group of brain regions with lower activity during externally-directed tasks and higher activity if tasks require internal focus. Recently, however, researchers at Stanford University School of Medicine recorded electrical activity directly from a core DMN component known as the posteromedial cortex (PMC) during both internally- and externally-directed waking states – specifically, autobiographical memory and arithmetic calculation, respectively. The data they recorded showed an inverse relationship – namely, the degree activation during memory retrieval predicted the degree of suppression during arithmetic calculation – which they say provides important anatomical and temporal details about DMN function at the neural population level.
New algorithm can analyze information from medical images to identify diseased areas of the brain and connections with other regions.
Disorders such as schizophrenia can originate in certain regions of the brain and then spread out to affect connected areas. Identifying these regions of the brain, and how they affect the other areas they communicate with, would allow drug companies to develop better treatments and could ultimately help doctors make a diagnosis. But interpreting the vast amounts of data produced by brain scans to identify these connecting regions has so far proved impossible.
Now, researchers in the Computer Science and Artificial Intelligence Laboratory at MIT have developed an algorithm that can analyze information from medical images to identify diseased areas of the brain and their connections with other regions.
The MIT researchers will present the work next month at the International Conference on Medical Image Computing and Computer Assisted Intervention in Nice, France.
Reduced Brain Connections Seen in People With Generalized Anxiety Disorder
A new University of Wisconsin-Madison imaging study shows the brains of people with generalized anxiety disorder (GAD) have weaker connections between a brain structure that controls emotional response and the amygdala, which suggests the brain’s “panic button” may stay on due to lack of regulation.
Anxiety disorders are the most common class of mental disorders and GAD, which is characterized by excessive, uncontrollable worry, affects nearly 6 percent of the population.
Lead author Dr. Jack Nitschke, associate professor of psychiatry in the UW School of Medicine and Public Health, says the findings support the theory that reduced communications between parts of the brain explains the intense anxiety felt by people with GAD.
In this case, two types of scans showed the amygdala, which alerts us to threat in our surroundings and initiates the “fight-or-flight” response, seems to have weaker “white matter” connections to the prefrontal and anterior cingulate cortex (ACC), the center of emotional regulation.
The researchers did two types of imaging - diffusion tensor imaging (DTI) and functional magnetic resonance (fMRI) - on the brains of 49 GAD patients and 39 healthy volunteers. Compared with the healthy volunteers, the imaging showed the brains of people with GAD had reduced connections between the prefrontal and anterior cingulate cortex and the amygdala via the uncinate fasciculus, a primary “white matter” tract that connects these brain regions. This reduced connectivity was not found in other white matter tracts elsewhere in their brains.
"We know that in the brain, if you use a circuit you build it up, the way you build muscle by exercise,” says Nitschke, a clinical psychologist who treats patients with anxiety disorders and does research at the UW-Madison’s Waisman Center.
Nitschke says that researchers wonder if this weak connection results in the intense anticipatory anxiety and worry that is the hallmark of GAD, because the ACC is unable to tell the amygdala to “chill out.” It also suggests that behavioral therapy that teaches patients to consciously exercise this emotional regulation works to reduce anxiety by strengthening the connection.
"It’s possible that this is exactly what we’re doing when we teach patients to regulate their reactions to the negative events that come up in everyone’s lives,” Nitschke says. "We can help build people’s tolerance to uncontrollable future events by teaching them to regulate their emotions to the uncertainty that surrounds those events.
(Source: news.wisc.edu)
A pain map of the brain being developed by scientists could finally put an end to the debate about whether women suffer more pain than men.
Using brain scanning technology, neuroscientists have been able to see how the brain responds to pain and map the signals to different parts of the body. They have also been able to measure how much pain someone is in from the signals in the brain.
Standard head movements made while exposed to one of the three electromagnetic fields produced by a heavy duty MRI scanner seem to temporarily lower concentration and visuospatial awareness, shows an experimental study published online in Occupational and Environmental Medicine.
Thirty one volunteers made standard head movements within the static magnetic field of a higher field 7 Tesla MRI scanner at exposure levels of zero (sham), 0.5 (medium), and 1 (high)Tesla, in a random order, one week apart.
After each exposure level, the volunteers were set 12 timed cognitive tasks, designed to test the sorts of skills that a surgeon or other healthcare professional might need to deploy within the vicinity of an MRI scanner.
These included visual tracking and movement, as well as more general functions, such as attention, concentration and working memory. The tests were neutral in that they didn’t test intelligence or depend on practice.
In all, 30 volunteers completed all three sessions. Compared with the sham test, the results showed that the more general functions, such as attention and concentration, and visuospatial awareness were significantly affected.
Neuroscientist David Sulzer Turns Brain Waves Into Music
Columbia neurophysiologist David Sulzer took his first piano lessons at the age of 11 and was playing his violin and guitar in bars by age 15. Later he gained a national following as a founder of the Soldier String Quartet and the Thai Elephant Orchestra—an actual orchestra of elephants in northern Thailand—and for playing with the likes of Bo Diddley, the Velvet Underground’s John Cale and the jazz great Tony Williams.
From left, Brad Garton and David Sulzer discuss turning brain waves into music on WHYY/PBS in Philadelphia.
It was only after arriving at Columbia, however, that the musician-turned-research-scientist embarked on perhaps his most exotic musical venture—using a computer to translate the spontaneous patterns of his brain waves into music.
With the help of Brad Garton, director of Columbia’s Computer Music Center, Sulzer has performed his avant-garde brain wave music in solo recitals and with musical ensembles.
Last spring, Sulzer presented a piece entitled Reading Stephen Colbert at a conference in New York City sponsored by Columbia and the Paris-based IRCAM (Institut de Recherche et Coordination Acoustique/Musique), a global center of musical research.
Sulzer, a professor in the departments of Psychiatry, Neurology and Pharmacology, wore electrodes attached to his scalp to measure voltage fluctuations in his brain as he sat in a chair reading a book by the comedian. Those fluctuations were fed into a computer program created by Garton, which transformed them into musical notes.
MRI Findings Shed Light On Multiple Sclerosis
ScienceDaily (Aug. 21, 2012) — New magnetic resonance imaging (MRI) research shows that changes in brain blood flow associated with vein abnormalities are not specific for multiple sclerosis (MS) and do not contribute to its severity, despite what some researchers have speculated. Results of the research are published online in the journal Radiology.
"MRI allowed an accurate evaluation of cerebral blood flow that was crucial for our results," said Simone Marziali, M.D., from the Department of Diagnostic Imaging at the University of Rome Tor Vergata in Rome.
MS is a disease of the central nervous system in which the body’s immune system attacks the nerves. There are different types of MS, and symptoms and severity vary widely. Recent reports suggest a highly significant association between MS and chronic cerebrospinal venous insufficiency (CCSVI), a condition characterized by compromised blood flow in the veins that drain blood from the brain. This strong correlation has generated substantial attention from the scientific community and the media in recent years, raising the possibility that MS can be treated with endovascular procedures like stent placement. However, the role of brain blood flow alterations on MS patients is still unclear.
To investigate this further, Italian researchers compared brain blood flow in 39 MS patients and 26 healthy control participants. Twenty-five of the MS patients and 14 of the healthy controls were positive for CCSVI, based on Color-Doppler-Ultrasound (CDU) findings. The researchers used dynamic susceptibility contrast-enhanced (DSC) MRI to assess blood flow in the brains of the study groups. DSC MR imaging offers more accurate assessment of brain blood flow than that of CDU. MRI and CDU were used to assess two different anatomical structures.
While CCSVI-positive patients showed decreased cerebral blood flow and volume compared with their CCSVI-negative counterparts, there was no significant interaction between MS and CCSVI for any of the blood flow parameters. Furthermore, the researchers did not find any correlation between the cerebral blood flow and volume in the brain’s white matter and the severity of disability in MS patients.
The results suggest that CCSVI is not a pathological condition correlated with MS, according to Dr. Marziali, but probably just an epiphenomenon — an accessory process occurring in the course of a disease that is not necessarily related to the disease. This determination is important because, to date, studies of the prevalence of CCSVI in MS patients have provided inconclusive results.
"This study clearly demonstrates the important role of MRI in defining and understanding the causes of MS," Dr. Marziali said. "I believe that, in the future, it will be necessary to use powerful and advanced diagnostic tools to obtain a better understanding of this and other diseases still under study."
Source: Science Daily
A technique called high-definition fiber tractography (HDFT) provides a powerful new tool for tracing the course of nerve fiber connections within the brain — with the potential to improve the accuracy of neurosurgical planning and to advance scientific understanding of the brain’s structural and functional networks, reports a paper in the August issue of Neurosurgery, official journal of the Congress of Neurological Surgeons.
MRI of human skull (sagittal view)