Posts tagged fMRI
Articles and news from the latest research reports.
The image of mental fatigue
Functional magnetic resonance imaging offers insights into mental fatigue
We all perhaps know the feeling of mental exhaustion, but what does it mean physiologically to have mental fatigue? A new study carried out using brain scans could help scientists uncover the neurobiological mechanisms underlying mental fatigue.
According to Bui Ha Duc and Xiaoping Li of the National University of Singapore writing in a forthcoming issue of the International Journal Computer Applications in Technology, mental fatigue has become commonplace as many people face increasing mental demands from stressful jobs, longer working hours with less time to relax and increasingly suffer sleep problems. Mental fatigue has received attention from those involved generally in health and well being as well as from the military and transport industry. After all, mental fatigue not only affects the health of individuals but can also have implications for road safety and international security.
The researchers used functional magnetic resonance imaging (fMRI) to monitor activity in the brains of ten student volunteers (male and female aged 19 to 25 years) deprived of sleep for 25 hours and given a simple task repeatedly through that period. They carried out scans at 9am, 2pm, 3am, 9am the following day. All volunteers had to have avoided alcohol and caffeine for the 24 hours prior to the experiment, were all physically and mentally fit prior to participation and none had any sleep problems.
The activation of the left thalamus increases with sleep deprivation, going in an exactly opposite trend to the inferior parietal that (following the circadian rhythm) decreases in activation from 9 am to 3 am next day and then increases in activation. This finding fits with logic as the inferior parietal cortex integrates information from different sensory modalities. As all the information has to go through the thalamus and then is sent by the thalamus to the inferior parietal, when the inferior parietal decreases in activation, the thalamus must increase its activation to get the information sent through.
The team explains that a gradual increase in mental fatigue led to decreased activity in the volunteers’ brains in specific regions: the anterior cingulate gyrus, right inferior frontal, left middle frontal and right superior temporal cortex. The anterior cingulate cortex has been described as an interface between motivation, cognition and action, and has been implicated in using reinforcement information to control behavior. The fMRI scans suggest that decreased activity in this part of the brain is therefore linked to those familiar feelings of mental fatigue including lethargy and slowness of thinking.
"The research provides a neurophysiologic basis for measuring the level of mental fatigue by EEG, as well as for the intervention by non-invasive neural stimulation to maintain wakefulness," the team says. "We have developed devices for both, which will be commercialized by our spinoff company, Newrocare Pte Ltd."
(Source: eurekalert.org)
Where does it hurt? Pain map discovered in the human brain
Scientists have revealed the minutely detailed pain map of the hand that is contained within our brains, shedding light on how the brain makes us feel discomfort and potentially increasing our understanding of the processes involved in chronic pain.
The map, uncovered by scientists at UCL, is the first to reveal how finely-tuned the brain is to pain. Published in the Journal of Neuroscience, the study uses fMRI techniques in conjunction with laser stimuli to the fingers to plot the exact response to pain across areas of the brain.
“The results reveal that pain can be finely mapped in the brain,” said lead author Dr Flavia Mancini (UCL Institute of Cognitive Neuroscience). “While many studies have examined the brain response to pain before, our study is the first to map pain responses for the individual digits of the human hand.”
Using an fMRI brain imaging technique originally created to map the visual field, the researchers were able to distinguish the brain’s responses to painful laser heat stimuli on each finger in seven healthy participants, and to study their organisation in the brain.
This enabled the team to produce a fine-grained map showing how pain in the right hand results in certain parts of the brain being activated in the primary somatosensory cortex, an area in the left hemisphere of the brain which is involved in processing bodily information.
When comparing this pain map to ones generated by non-painful touch to the right hand, the researchers found that the two were very similar, with each map aligning with one another in each of the seven volunteers tested.
“The cells in the skin that respond to pain and the cells that respond to touch have very different structures and distributions, so we were surprised to find that the maps of pain and of touch were so similar in the brain,” said Dr Mancini. “The striking alignment of pain and touch maps suggests powerful interactions between the two systems.”
The pain maps could be used to provide markers for the location of pain in the human brain, enabling clinicians to see how patients’ brains reorganise following chronic pain.
“We know that the organisation of other sensory maps in the brain is altered in patients with chronic pain,” said Professor Patrick Haggard (UCL Institute of Cognitive Neuroscience). “Our method could next be used to track the reorganisation of brain maps that occurs in chronic pain, providing new insights into how the brain makes us feel pain. Therefore, measuring the map for pain itself is highly important.”
(Source: ucl.ac.uk)
Researchers find reading uses the same brain regions regardless of language
A team of French and Taiwanese researchers has found evidence to indicate that people use the same regions of the brain when reading, regardless of which language is being read. In their paper published in the Proceedings of the National Academy of Sciences, they describe how fMRI brain scans made while people were reading revealed that there are very few differences in how the brain works as reading occurs.
The researchers note that previous research has suggested that different neural networks might be involved when people read text written in very different types of languages. French, for example, is an alphabetic language, whereas Chinese is logographic. Those of Roman origin are based on abstract concepts while Chinese characters are based on realistic depictions of handwriting strokes.
To learn more, the researchers ran fMRI scans on volunteers reading either Chinese or French material as their native language. The material presented was shown in various forms, e.g. normal, static, backwards or distorted. The researchers also employed priming, which is where words are flashed on a screen for such a short period of time as to be unknown to the reader. Priming has been found to influence the rate at which readers recognize words that are shown thereafter for a normal duration of time. The material written in French was presented as cursive rather than block printed letters.
In analyzing the results, the researchers found the differences in brain activity between the two groups as they read to be minimal. Those differences that were found, centered around a slight increase in the brain regions associated with processing the physical movements that had occurred in creating the characters, which in the brain is recognized as motor skills.
The researchers suggest that their results indicate that because reading is a relatively new process for the human brain, it likely evolved using previously existing neural network circuitry, which would explain why it appears the brain works in roughly the same way when reading, regardless of language.
How Does the Brain Process Art?
New imaging techniques are mapping the locations of our aesthetic response
In Michelangelo’s Expulsion from Paradise, a fresco panel on the ceiling of the Sistine Chapel, the fallen-from-grace Adam wards off a sword-wielding angel, his eyes averted from the blade and his wrist bent back defensively. It is a gesture both wretched and beautiful. But what is it that triggers the viewer’s aesthetic response—the sense that we’re right there with him, fending off blows?
Recently, neuroscientists and an art historian asked ten subjects to examine the wrist detail from the painting, and—using a technique called transcranial magnetic stimulation (TMS)—monitored what happened in their brains. The researchers found that the image excited areas in the primary motor cortex that controlled the observers’ own wrists.
“Just the sight of the raised wrist causes an activation of the muscle,” reports David Freedberg, the Columbia University art history professor involved in the study. This connection explains why, for instance, viewers of Degas’ ballerinas sometimes report that they experience the sensation of dancing—the brain mirrors actions depicted on the canvas.
Freedberg’s study is part of the new but growing field of neuroaesthetics, which explores how the brain processes a work of art. The discipline emerged 12 years ago with publication of British neuroscientist Semir Zeki’s book, Inner Vision: An Exploration of Art and the Brain. Today, related studies depend on increasingly sophisticated brain-imaging techniques, including TMS and functional magnetic resonance imaging (fMRI), which maps blood flow and oxygenation in the brain. Scientists might monitor an observer’s reaction to a classical sculpture, then warp the sculpture’s body proportions and observe how the viewer’s response changes. Or they might probe what occurs when the brain contemplates a Chinese landscape painting versus an image of a simple, repetitive task.
Ulrich Kirk, a neuroscientist at the Virginia Tech Carilion Research Institute, is also interested in artworks’ contexts. Would a viewer respond the same way to a masterpiece enshrined in the Louvre if he beheld the same work displayed in a less exalted setting, such as a garage sale? In one experiment, Kirk showed subjects a series ofimages—some, he explained, were fine artwork; others were created by Photoshop. In reality, none were Photoshop-generated; Kirk found that different areas of viewers’ brains fired up when he declared an image to be “art.”
Kirk also hopes one day to plumb the brains of artists themselves. “You might be able to image creativity as it happens, by putting known artists in the fMRI,” he says.
Others, neuroscientists included, worry that neuroscience offers a reductionist perspective. Vilayanur Ramachandran, a neuroscientist at the University of California at San Diego, says that neuroaesthetics undoubtedly “enriches our understanding of human aesthetic experience.” However, he adds, “We have barely scratched the surface…the quintessence of art, and of genius, still eludes us—and may elude us forever.”
(Source: smithsonianmag.com)
Will Neuroscience Radically Transform the Legal System?
Although academic fields will often enjoy more than Andy Warhol’s famous 15 minutes of fame, they too are subject to today’s ever-hungry machinery of hype. Like people, bands, diets, and everything else, a field gets discovered, plucked from obscurity, thrown into the spotlight, and quickly replaced as it becomes yesterday’s news.
Neuroscience is now the popular plat de jour, or, perhaps better, the prefixde jour, and neurolaw is one of the main beneficiaries—and victims. Neuroscience will have important and even dramatic effects on our society and, as a result, on our laws. But not yet, and not as dramatically as some envision.
First, consider timing. Many of the most interesting neuroscience results come from functional magnetic resonance imaging (fMRI). This technique allows us to see what parts of the brain are working and when, and thus to begin to correlate subjective mental states with physical brain states. The use of fMRI on humans goes back about 15 years, and although about 5,000 peer-reviewed scientific articles involving fMRI will be published this year, we are still trying to figure out how it works—or doesn’t. The fMRI results showing apparently purposeful brain activity in dead salmon are a wonderfully funny example of some of the limits of this technology, and fMRI is one of the oldest of the “new” neuroscience technologies. Half of what neuroscience is teaching us about human brain function will be shown, in the next 20 years, to be wrong—and we will need each of those 20 years to figure out which half.
But, second, we need a sense of proportion. Neuroscience will provide tools that will change the law in some important ways, but those tools will be neither perfect nor used in isolation, and those changes are not likely to strike at the law’s roots.
Study links hippocampus with unconscious bias
The hippocampus is an area of the brain known to be one in which links between memories are formed, but until now it was not known that this brain region is involved in steering the brain towards making particular choices over others when faced with new decisions for which we have no previous experiences to draw on.
In a paper published in the journal Science, research psychologists G. Elliott Wimmer and Daphna Shohamy of Columbia University in New York report on their study, which used functional magnetic resonance imaging (fMRI) of regions of the brain. In the study, they asked 31 volunteers to complete a three-part task while in the machine. Throughout the task their brain activity was determined by the fMRI.
The results suggest that several areas of the brain are involved in evaluating new stimuli and associating them with previous memories, but the process is strongly associated with the hippocampus.
The findings could have application, for example, in the design of new products, which could incorporate aspects of earlier products (such as color, logo or font) to stimulate the association and produce an unconscious bias towards those products over other equally new products.
The findings also suggest that misguided biases such as racism could stem from unconscious associations. (Guilt by association is a commonly known bias.) These biases have long been known, but the current study clearly shows their association with the hippocampus.
Training computers to understand the human brain
Understanding how the human brain categorizes information through signs and language is a key part of developing computers that can ‘think’ and ‘see’ in the same way as humans. Hiroyuki Akama at the Graduate School of Decision Science and Technology, Tokyo Institute of Technology, together with co-workers in Yokohama, the USA, Italy and the UK, have completed a study using fMRI datasets to train a computer to predict the semantic category of an image originally viewed by five different people.
The participants were asked to look at pictures of animals and hand tools together with an auditory or written (orthographic) description. They were asked to silently ‘label’ each pictured object with certain properties, whilst undergoing an fMRI brain scan. The resulting scans were analysed using algorithms that identified patterns relating to the two separate semantic groups (animal or tool).
After ‘training’ the algorithms in this way using some of the auditory session data, the computer correctly identified the remaining scans 80-90% of the time. Similar results were obtained with the orthographic session data. A cross-modal approach, namely training the computer using auditory data but testing it using orthographic, reduced performance to 65-75%. Continued research in this area could lead to systems that allow people to speak through a computer simply by thinking about what they want to say.
Nearly 100 years after a British neurologist first mapped the blind spots caused by missile wounds to the brains of soldiers, Perelman School of Medicine researchers at the University of Pennsylvania have perfected his map using modern-day technology. Their results create a map of vision in the brain based upon an individual’s brain structure, even for people who cannot see. Their result can, among other things, guide efforts to restore vision using a neural prosthesis that stimulates the surface of the brain. The study appears in the latest issue of Current Biology, a Cell Press journal.
Not getting sleepy? Research explains why hypnosis doesn’t work for all
Not everyone is able to be hypnotized, and new research from the Stanford University School of Medicine shows how the brains of such people differ from those who can easily be.
The study, published in the October issue of Archives of General Psychiatry, uses data from functional and structural magnetic resonance imaging to identify how the areas of the brain associated with executive control and attention tend to have less activity in people who cannot be put into a hypnotic trance.
“There’s never been a brain signature of being hypnotized, and we’re on the verge of identifying one,” said David Spiegel, MD, the paper’s senior author and a professor of psychiatry and behavioral sciences. Such an advance would enable scientists to understand better the mechanisms underlying hypnosis and how it can be used more widely and effectively in clinical settings, added Spiegel, who also directs the Stanford Center for Integrative Medicine.
Spiegel estimates that one-quarter of the patients he sees cannot be hypnotized, though a person’s hypnotizability is not linked with any specific personality trait. “There’s got to be something going on in the brain,” he said.
Study explores how brain disruption may foster schizophrenia
Yale University researchers have discovered an innovative way to study how large brain systems are organized, an advance that has already provided insights into diseases such as schizophrenia.
The Yale team used a combination of neuroimaging, computational neurobiology, and pharmacological techniques to reveal functioning at both the cellular level and across larger brain regions.
In a paper in Proceedings of the National Academy of Sciences the week of Sept. 24, Yale scientists use this approach to show that a disruption of a particular signaling mechanisms within larger neural systems may be contribute to schizophrenia symptoms.