Right or left? Brain stimulation can change which hand you favor

Right or left? Brain stimulation can change which hand you favor
September 27th, 2010 in Medicine & Health / Neuroscience

Each time we perform a simple task, like pushing an elevator button or reaching for a cup of coffee, the brain races to decide whether the left or right hand will do the job. But the left hand is more likely to win if a certain region of the brain receives magnetic stimulation, according to new research from the University of California, Berkeley.

UC Berkeley researchers applied transcranial magnetic stimulation (TMS) to the posterior parietal cortex region of the brain in 33 right-handed volunteers and found that stimulating the left side spurred an increase in their use of the left hand.

The left hemisphere of the brain controls the motor skills of the right side of the body and vice versa. By stimulating the parietal cortex, which plays a key role in processing spatial relationships and planning movement, the neurons that govern motor skills were disrupted.

"You're handicapping the right hand in this competition, and giving the left hand a better chance of winning," said Flavio Oliveira, a UC Berkeley postdoctoral researcher in psychology and neuroscience and lead author of the study, published this week in the journal Proceedings of the National Academy of Sciences.

The study's findings challenge previous assumptions about how we make decisions, revealing a competitive process, at least in the case of manual tasks. Moreover, it shows that TMS can manipulate the brain to change plans for which hand to use, paving the way for clinical advances in the rehabilitation of victims of stroke and other brain injuries.

"By understanding this process, we hope to be able to develop methods to overcome learned limb disuse," said Richard Ivry, UC Berkeley professor of psychology and neuroscience and co-author of the study.

At least 80 percent of the people in the world are right-handed, but most people are ambidextrous when it comes to performing one-handed tasks that do not require fine motor skills.

"Alien hand syndrome," a neurological disorder in which victims report the involuntary use of their hands, inspired researchers to investigate whether the brain initiates several action plans, setting in motion a competitive process before arriving at a decision.

While the study does not offer an explanation for why there is a competition involved in this type of decision making, researchers say it makes sense that we adjust which hand we use based on changing situations.
"In the middle of the decision process, things can change, so we need to change track," Oliveira said.

In TMS, magnetic pulses alter electrical activity in the brain, disrupting the neurons in the underlying brain tissue. While the current findings are limited to hand choice, TMS could, in theory, influence other decisions, such as whether to choose an apple or an orange, or even which movie to see, Ivry said.

With sensors on their fingertips, the study's participants were instructed to reach for various targets on a virtual tabletop while a 3-D motion-tracking system followed the movements of their hands. When the left posterior parietal cortex was stimulated, and the target was located in a spot where they could use either hand, there was a significant increase of the use of the left hand, Oliveira said.

Provided by University of California -- Berkeley

Why science can't hold sway

Our biases are overpowering.

By Faye Flam

Inquirer Staff Writer
Why do so many Americans disagree with scientific consensus on issues such as global climate change and the safety of burying nuclear waste? Is it our poor education? Science illiteracy? Innumeracy?

None of the above, according to a new study published in Journal of Risk Research. People's positions on these issues and their willingness to believe or discount scientists depends mostly on ideology, or what the study's authors call "cultural cognition."

After surveying 1,500 people, the researchers found that those who were "egalitarian and resentful of economic inequality" were more likely to assume that there was scientific consensus that human activity is contributing to climate change, but not that it's safe to dispose of nuclear waste underground. Those who were more "hierarchical, individualistic and connected to industry and commerce" were more likely to make the opposite assumptions.

According to reports from the National Academy of Sciences, human activity is contributing to climate change and nuclear waste can be buried safely in certain designated sites.

"It's not that one group is paying more attention to what scientific consensus is," said Dan Kahan, a law professor at Yale and author of the study. But there's a pervasive tendency to form perceptions of scientific consensus that reinforce people's values.

The researchers also confronted subjects with fictional authors - Robert Linden, professor of meteorology at MIT; Oliver Roberts, professor of nuclear engineering at U.C. Berkeley; and James Williams, professor of criminology at Stanford. All had Ivy League Ph.D.s and membership in the National Academy of Sciences.

Subjects were asked whether they'd recommend a book by any of these authors to a friend.

The result: The experts could be seen as sages or stooges depending on whether they were said to agree with a subject's preexisting belief.

Sure, professor Roberts might have a Ph.D. from Princeton but if he's going to panic about nuclear waste he must be a girly man - or if he thinks it's safe to bury it, someone in the nuclear industry must be paying him.

It's not that people don't like science - it's that they selectively attend to evidence in a way that's gratifying to them, said Kahan. "People will do that with our article," he said. "They'll say that's why those people [who disagree with them] are so dumb."


Read more: http://www.philly.com/inquirer/magazine/20100920_Why_science_can_t_hold_sway.html#ixzz10YUuI1Ph
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Vegetative state patients may soon be able to communicate

Vegetative state patients may soon be able to communicate
September 22nd, 2010 in Medicine & Health / Neuroscience
Communication in the vegetative state (Owen et al., Science, 2006; Monti et al., NEJM, 2010)

Researchers from Cambridge University in the UK have been able to communicate with brain-injured patients in "locked states" commonly referred to as persistent vegetative states (PVS). They predict such patients will soon be able to communicate and perhaps even move themselves around in motorized wheelchairs.

Neuroscientist Dr. Adrian Owen and colleagues used electroencephalography (EEG) monitors connected to 128 electrodes in a cap placed on the heads of brain injured patients, and were able to understand responses from them. Own thinks a similar system connected to a computer will be able to decode messages from their brains and allow them to communicate via a voice synthesizer and even control a motorized wheelchair. These systems could be available within a decade.

Dr. Owen used functional magnetic resonance imaging (fMRI) brain scans to prove that one PVS victim could understand queries and give “yes” or “no” answers to simple questions. The 29-year-old male patient had suffered brain damage in a car accident in 2003, and had been in a coma for two years before entering a persistent vegetative state. He appeared to be awake and blinked occasionally, but otherwise showed no signs of awareness.

The team used the fMRI scanner to measure the patient’s brain response while asking him questions. Brain signals associated with “yes” and “no” are complex and quite similar, and to overcome this problem the researchers asked the patient to imagine playing tennis for “yes” and walking through his home for “no”. Tennis movements activate regions at the top of the brain associated with spatial activities, while moving around the home is a navigational task that activates areas in the base of the brain. Using this technique the patient was able to correctly answer six test questions.

The team has now shown that similar responses could be achieved using EEG monitors, which measure electrical activity in the brain. EEG has the advantages of being much cheaper, smaller, and more portable than fMRI, which uses magnetic fields and radio waves to detect electrical pulses in the brain. EEG also gives results much more quickly than fMRI, making a conversation possible.

Dr. Owen said “we have seen something that is quite extraordinary” and that we now have a moral and ethical obligation to find ways to help patients in persistent vegetative states to communicate. The communication will be via yes/no questions, but he said “you can get a long way with yes/no questions.”

The research findings suggest about 20 percent of PVS sufferers could be able to communicate, and this may raise questions about switching off life support systems for such patients.

Dr. Owen and several members of team will soon be transferring to research posts at the University of Western Ontario in Canada, where they will receive a grant worth around 20 million US dollars to continue the research.

More information: -- Monti MM, Vanhaudenhuyse A, Coleman MR, Boly M, Pickard JD, Tshibanda L, Owen AM, Laureys S (2010), “Willful modulation of brain activity in disorders of consciousness.” N Engl J Med 362(7):579-89
-- Owen AM, Coleman MR, Davis MH, Boly M, Laureys S, Pickard JD (2006), “Detecting awareness in the vegetative state” Science 313:1402

For neurons to work as a team, it helps to have a beat

For neurons to work as a team, it helps to have a beat
September 20th, 2010 in Medicine & Health / Neuroscience

When it comes to conducting complex tasks, it turns out that the brain needs rhythm, according to researchers at the University of California, Berkeley.

Specifically, cortical rhythms, or oscillations, can effectively rally groups of neurons in widely dispersed regions of the brain to engage in coordinated activity, much like a conductor will summon up various sections of an orchestra in a symphony.

Even the simple act of catching a ball necessitates an impressive coordination of multiple groups of neurons to perceive the object, judge its speed and trajectory, decide when it's time to catch it and then direct the muscles in the body to grasp it before it whizzes by or drops to the ground.

Until now, neuroscientists had not fully understood how these neuron groups in widely dispersed regions of the brain first get linked together so they can work in concert for such complex tasks.

The UC Berkeley findings are to be published the week of Sept. 20 in the online early edition of the journal Proceedings of the National Academy of Sciences.

"One of the key problems in neuroscience right now is how you go from billions of diverse and independent neurons, on the one hand, to a unified brain able to act and survive in a complex world, on the other," said principal investigator Jose Carmena, UC Berkeley assistant professor at the Department of Electrical Engineering and Computer Sciences, the Program in Cognitive Science, and the Helen Wills Neuroscience Institute. "Evidence from this study supports the idea that neuronal oscillations are a critical mechanism for organizing the activity of individual neurons into larger functional groups."

The idea behind anatomically dispersed but functionally related groups of neurons is credited to neuroscientist Donald Hebb, who put forward the concept in his 1949 book "The Organization of Behavior."

"Hebb basically said that single neurons weren't the most important unit of brain operation, and that it's really the cell assembly that matters," said study lead author Ryan Canolty, a UC Berkeley postdoctoral fellow in the Carmena lab.

It took decades after Hebb's book for scientists to start unraveling how groups of neurons dynamically assemble. Not only do neuron groups need to work together for the task of perception - such as following the course of a baseball as it makes its way through the air - but they then need to join forces with groups of neurons in other parts of the brain, such as in regions responsible for cognition and body control.

At UC Berkeley, neuroscientists examined existing data recorded over the past four years from four macaque monkeys. Half of the subjects were engaged in brain-machine interface tasks, and the other half were participating in working memory tasks. The researchers looked at how the timing of electrical spikes - or action potentials - emitted by nerve cells was related to rhythms occurring in multiple areas across the brain.

Among the squiggly lines, patterns emerged that give literal meaning to the phrase "tuned in." The timing of when individual neurons spiked was synchronized with brain rhythms occurring in distinct frequency bands in other regions of the brain. For example, the high-beta band - 25 to 40 hertz (cycles per second) - was especially important for brain areas involved in motor control and planning.

"Many neurons are thought to respond to a receptive field, so that if I look at one motor neuron as I move my hand to the left, I'll see it fire more often, but if I move my hand to the right, the neuron fires less often," said Carmena. "What we've shown here is that, in addition to these traditional 'external' receptive fields, many neurons also respond to 'internal' receptive fields. Those internal fields focus on large-scale patterns of synchronization involving distinct cortical areas within a larger functional network."

The researchers expressed surprise that this spike dependence was not restricted to the neuron's local environment. It turns out that this local-to-global connection is vital for organizing spatially distributed neuronal groups.

"If neurons only cared about what was happening in their local environment, then it would be difficult to get neurons to work together if they happened to be in different cortical areas," said Canolty. "But when multiple neurons spread all over the brain are tuned in to a specific pattern of electrical activity at a specific frequency, then whenever that global activity pattern occurs, those neurons can act as a coordinated assembly."

The researchers pointed out that this mechanism of cell assembly formation via oscillatory phase coupling is selective. Two neurons that are sensitive to different frequencies or to different spatial coupling patterns will exhibit independent activity, no matter how close they are spatially, and will not be part of the same assembly. Conversely, two neurons that prefer a similar pattern of coupling will exhibit similar spiking activity over time, even if they are widely separated or in different brain areas.

"It is like the radio communication between emergency first responders at an earthquake," Canolty said. "You have many people spread out over a large area, and the police need to be able to talk to each other on the radio to coordinate their action without interfering with the firefighters, and the firefighters need to be able to communicate without disrupting the EMTs. So each group tunes into and uses a different radio frequency, providing each group with an independent channel of communication despite the fact that they are spatially spread out and overlapping."

The authors noted that this local-to-global relationship in brain activity may prove useful for improving the performance of brain-machine interfaces, or lead to novel strategies for regulating dysfunctional brain networks through electrical stimulation. Treatment of movement disorders through deep brain stimulation, for example, usually targets a single area. This study suggests that gentler rhythmic stimulation in several areas at once may also prove effective, the authors said.

Provided by University of California -- Berkeley

How does Prozac act?

How does Prozac act? By acting on the microRNA
September 16th, 2010 in Medicine & Health / Research


The adaptation mechanisms of the neurons to antidepressants has, until now, remained enigmatic. Research, published this week by teams of Odile Kellermann and of Jean-Marie Launay (Inserm, Paris), sheds new light on the mechanisms of action of these drugs which have been used for more than 30 years and are heavily consumed.

The response time to antidepressants, such as Prozac, is around three weeks. How can we explain this? The adaptation mechanisms of the neurons to antidepressants has, until now, remained enigmatic. Research, published this week by the teams of Odile Kellermann (Inserm Unit 747 Cellules souches, Signalisation et Prions, Universite Paris-Descartes) and of Jean-Marie Launay (Inserm Unit 942 Hôpital Lariboisicre, Paris and the mental health network, Santé Mentale), sheds new light on the mechanisms of action of these drugs which have been used for more than 30 years and are heavily consumed over the world. In particular, the researchers have revealed, for the first time, a sequence of reactions caused by Prozac at the neuron level, which contributes to an increase in the amounts of serotonin, a chemical "messenger" essential to the brain, and deficient in depressive individuals.

Details of this work are published in the journal Science dated 17 September 2010.

Depressive states are associated with a deficit of serotonin (5-HT), one of the neurotransmitters essential for communication between neurons and particularly involved in eating and sexual behaviours, the sleep-wake cycle, pain, anxiety and mood problems.

Strategies employing antidepressant class I molecules, developed since the 1960s are thus primarily aimed at increasing the quantity of serotonin released in the synaptic gap, the space between two neurons, where the nervous communications take place via the neurotransmitters. Although it has been known for several years that antidepressants like Prozac have the effect of increasing the concentration of serotonin by blocking its recapture by the serotonin transporter (SERT) in the synapses, we did not hitherto know how to explain the delay in their action (3 weeks).

The teams of Odile Kellermann and of Jean-Marie Launay, in close collaboration with Hoffmann-LaRoche (Basel), have now characterised, for the first time, in vitro and then in vivo, the various reactions and intermediate molecules produced in the presence of Prozac, which are eventually responsible for an increased release of serotonin. In particular, the researchers have identified the key role of one particular microRNA in the active mechanisms of the antidepressants on the brain*.

This microRNA, known as miR-16, controls synthesis of the serotonin transporter.

Under normal physiological conditions, this transporter is present in the so-called "serotonergic" neurons, i.e. neurons specialised in production of this neurotransmitter. However, expression of this transporter is reduced to zero by miR-16 in so-called "noradrenaline" neurons, another neurotransmitter involved in attention, emotions, sleep, dreaming and learning.

In response to Prozac, the serotonergic neurons release a signal molecule, which causes the quantity of miR-16 to drop, which unlocks expression of the serotonin transporter in the noradrenaline neurons.

These neurons become sensitive to Prozac. They continue to produce noradrenaline, but they become mixed: they also synthesise serotonin. Ultimately, the quantity of released serotonin is increased both in the serotonergic neurons, via the direct effect of the Prozac which prevents its recapture, and in the noradrenaline neurons through the reduction of miR-16.

Hence, "this will work has revealed, for the first time, that antidepressants are able to activate a new 'source' of serotonin in the brain", explain the researchers "Furthermore, our results demonstrate that the effectiveness of Prozac rests on the 'plastic' properties of the noradrenaline neurons, i.e. their capacity to acquire the functions of serotonergic neurons".

To elucidate the mode of action of Prozac, the researchers from the Ile-de-France region used neuron stem cells which were able to differentiate themselves into neurons for manufacturing serotonin or noradrenaline. The cells, isolated and characterised by the two research teams, allowed them to reveal using pharmacological and molecular approaches, the functional links between Prozac, miR-16, serotonin transporter and the signal-molecule trigger, known as S100Beta. These links observed in vitro have been validated in vivo in mice, in the serotonergic neurons of the raphe and the noradrenaline neurons in the locus coeruleus. Dialogue between these two areas of the brain, situated under the cortex in the brainstem, is therefore one of the keys to Prozac action.

Behavioural tests have moreover confirmed the importance of miR-16 as an intermediary in Prozac action.

These results open up new avenues of research for the treatment of depressive states. Each of the "actors" in the sequence of reactions initiated by Prozac constitutes a potential pharmacological target.

The pharmacological dynamics of antidepressants, i.e. the study of the speed of action of these molecules, should also be the subject of new investigations in light of these new ideas.

More information: "miR-16 Targets the Serotonin Transporter: A New Facet for Adaptive Responses to Antidepressants" Science, September 17th 2010, vol. 329, 5998.


Provided by INSERM

Two or three is all we see

Two or three is all we see
September 15th, 2010 in Medicine & Health / Research

The human brain can see only up to three moving objects at a given instant, new research has found.

The discovery has important implications for road design and safety, driver and pilot training, industrial safety, fast-moving sports and other areas of human visual activity affecting safety and performance.

“We have found that there is a limit to the maximum number of directions, and hence distinct objects, that the human brain can see at any given instant in time,” said Dr. Mark Edwards of The Vision Centre and The Australian National University.

“That limit is either two or three, depending upon how the directions are defined.”

“An example of this is when we’re at a road roundabout: although we can see cars coming and going in different directions, we can’t actually keep close tabs on more than three simultaneously. Rather, what the brain does is process them in series, like cars heading from the right, then in the roundabout, followed by cars on the left.”

The same theory also applies to multi-tasking, said Dr. Edwards: “We may assume that people who are good at multitasking can process lots of different things at once, but what may be closer to the reality is that they are actually able to switch their attention faster to the next item.”

Dr. Edwards and Dr. John Greenwood tested the brain’s ability to detect signal directions using random-dot stimuli. These stimuli consisted of a field of scattered dots, with groups of intermingled dots moving in different directions. They found that people could not detect more than two signal directions at once if those signals moved in different directions. The people could detect three signals when they differed in speed or depth.

However, once these limits were exceeded, instead of seeing distinct signals, what they saw was only randomly-moving noise.

Dr. Edwards explained that the limits of two and three occur for different reasons.

“In order to see motion, the signal intensity - proportion of dots moving in a given direction - needs to be of at least a certain value. For the transparent displays used here, that intensity level has to be over 40 per cent, said Dr. Edwards. “What this means is there has to be at least 40 per cent of the dots moving in a given direction to stimulate the brain cells that are processing that motion.”

Given that the dots that move in different directions act as noise for each other, this means that the maximum signal level that can be obtained with three directions, if all of those signals drive the same motion cells, is 33 per cent, a level that is too low to been seen.

However, our brain’s motion cells are also sensitive to different speeds and depth, so if the various signals not only move in different directions, but also at different speeds and depths, then they are processed by different motion cells, and so it is possible to get the signal intensity above 40 per cent even when many different signal directions are used.

However, when this is done, the maximum number of signals that can be perceived can only increase to three: far less than if the limit was due purely to signal-to-noise limitations.

“Clearly, there is another processing limit being imposed by the visual system, most likely an attentional bottleneck. To see more than three different directions of motion, and hence more than three moving objects, you have to selectively attend to them, one by one,” he explained.

Dr. Edwards said that the new insight into the ability of the average person to keep track of numerous moving objects has important health and safety implications for a whole range of areas such as road design and planning, operator training for vehicles, aircraft and for large equipment, sports training and other activities that demand a lot of our visual system.

Provided by Australian National University

Why some memores stick

Why some memories stick
Repetitive neural responses may enhance recall of faces and words.

Janelle Weaver

Faces that activate the same regions of the brain again and again are more likely to be remembered.
Pasieka / Science Photo Library

Practice makes perfect when it comes to remembering things, but exactly how that works has long been a mystery. A study published in Science this week1 indicates that reactivating neural patterns over and over again may etch items into the memory.

People find it easier to recall things if material is presented repeatedly at well-spaced intervals rather than all at once. For example, you're more likely to remember a face that you've seen on multiple occasions over a few days than one that you've seen once in one long period. One reason that a face linked to many different contexts — such as school, work and home — is easier to recognize than one that is associated with just one setting, such as a party, could be that there are multiple ways to access the memory. This idea, called the encoding variability hypothesis, was proposed by psychologists about 40 years ago2.

Each different context or setting activates a distinct set of brain regions; the hypothesis suggests that it is these differing neural responses that improve the memory. But neuroimaging research led by Russell Poldrack, a cognitive neuroscientist at the University of Texas, Austin, now suggests that the opposite is true — items are better remembered when they activate the same neural patterns with each exposure.

Neural rehearsal
Poldrack's team measured brain activity in 24 people using functional magnetic resonance imaging (fMRI). The subjects saw 120 unfamiliar faces, each one repeated four times at varying intervals during the fMRI scan. One hour later, they were shown the faces again, mixed with 120 new ones, and asked to rate the familiarity of each.

The researchers then looked at the brain responses that had been recorded when the subjects were first shown the faces, focusing on 20 brain regions associated with visual perception and memory. Faces that were later recognized evoked similar activation patterns at each repetition in nine of the regions, particularly those associated with object and face perception; faces that were later forgotten did not evoke such pattern to the same extent.

In a separate experiment, subjects in the fMRI scanner were shown 180 words, each repeated three times. Six hours later, they performed two memory tests. The remembered words elicited similar patterns at each repetition in 15 of the 20 brain regions that the researchers examined.

Explaining the brain
But Marvin Chun, a cognitive neuroscientist at Yale University in New Haven, Connecticut, says that the results do not invalidate the encoding variability hypothesis because Poldrack and his team were at a different type of situation. To directly test the hypothesis, the authors should have presented items in different contexts, he says.

What's more, attention-grabbing words or faces may elicit more reproducible patterns of activation when they are presented multiple times than do less striking items, says Rik Henson, a cognitive neuroscientist at the MRC Cognition and Brain Sciences Unit in Cambridge, UK. This effect could explain the results without refuting the encoding variability hypothesis, he adds.

"We can't rule that out," Poldrack says. To address this concern, he would have to further analyse subjects' brain responses to individual items. "It may well be the case that there is a version of the encoding variability hypothesis that is compatible with these data."

"If we push the theorists to think a little harder, and to try to incorporate neuroscience data into these theories, then I think that is a good thing, regardless of whether the encoding variability theory turns out to be right," he adds.

a.. References
1.. Xue, G. et al. Science doi:10.1126/science.1193125 (2010).
2.. Martin, E. Psych. Rev. 75, 421-441 (1968). | Article
Source: Nature
http://www.nature.com/news/2010/100909/full/news.2010.457.html