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Math ability requires crosstalk in the brain

September 9, 2012 Leave a comment

 

Examples of the simple numerical and arithmetic tasks used in the study. Participants were asked to judge whether the numerical operation was correct or not. Credit: Center for Vital Longevity, University of Texas at Dallas. (up)

A new study by researchers at UT Dallas’ Center for Vital Longevity, Duke University, and the University of Michigan has found that the strength of communication between the left and right hemispheres of the brain predicts performance on basic arithmetic problems. The findings shed light on the neural basis of human math abilities and suggest a possible route to aiding those who suffer from dyscalculia— an inability to understand and manipulate numbers.

It has been known for some time that the parietal cortex, the top/middle region of the brain, plays a central role in so-called numerical cognition—our ability to process numerical information. Previous brain imaging studies have shown that the right parietal region is primarily involved in basic quantity processing (like gauging relative amounts of fruit in baskets), while the left parietal region is involved in more precise numerical operations like addition and subtraction. What has not been known is whether the two hemispheres can work together to improve math performance. The new study demonstrates that they can. The findings were recently published online in Cerebral Cortex.

In the study, conducted in Dallas and led by Dr. Joonkoo Park, now a postdoctoral fellow at Duke University, researchers used functional magnetic resonance imaging, or fMRI, to measure the brain activity of 27 healthy young adults while they performed simple numerical and arithmetic tasks. In one task, participants were asked to judge whether two groups of shapes contained the same or different numbers of items. In two other tasks, participants were asked to solve simple addition and subtraction problems.

Consistent with previous studies, the researchers found that the basic number-matching task activated the right parietal cortex, while the addition and subtraction tasks produced additional activity in the left parietal cortex. But they also found something new: During the arithmetic tasks, communication between the left and right hemispheres increased significantly compared with the number-matching task. Moreover, people who exhibited the strongest connection between hemispheres were the fastest at solving the subtraction problems.

“Our results suggest that subtraction performance is optimal when there is high coherence in the neural activity in these two brain regions. Two brain areas working together rather than either region alone appears to be key” said co-author Dr. Denise C. Park, co-director of the UT Dallas Center for Vital Longevity and Distinguished University Chair in the School of Behavioral and Brain Sciences. Park (no relation to the lead author) helped direct the study along with Dr. Thad Polk, professor of psychology at the University of Michigan.

Lead author Dr. Joonkoo Park points out that the findings suggest that disrupted or inefficient neural communication between the hemispheres may contribute to the impaired math abilities seen in dyscalculia, the numerical equivalent of dyslexia. “If such a causal link exists,” he said, “one very interesting avenue of research would be to develop training tasks to enhance parietal connectivity and to test whether they improve numerical competence.”

Such a training program might help develop math ability in children and could also help older adults whose arithmetic skills begin to falter as a normal part of age-related cognitive decline.

 

Reference:

The above story is reprinted from materials provided by University of Texas at Dallas, via MedicalXpress.

Journal: Cerebral Cortex

 

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Mathematics or memory? Posterior Medial Cortex Study Charts Collision Course in Brain

September 8, 2012 Leave a comment

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.”

In a study to be 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. Parvizi is the study’s senior author. The first and second authors, respectively, are postdoctoral scholars Brett Foster, PhD, and Mohammed Dastjerdi, PhD.

Much of our understanding of what roles different parts of the brain play has been obtained by techniques such as functional magnetic resonance imaging, which measures the amount of blood flowing through various brain regions as a proxy for activity in those regions. But changes in blood flow are relatively slow, making fMRI a poor medium for listening in on the high-frequency electrical bursts (approximately 200 times per second) that best reflect nerve-cell firing. Moreover, fMRI typically requires pooling images from several subjects into one composite image. Each person’s brain physiognomy is somewhat different, so the blending blurs the observable anatomical coordinates of a region of interest.

Nonetheless, fMRI imaging has shown that the PMC is quite active in introspective processes such as autobiographical memory processing (“I ate breakfast this morning”) or daydreaming, and less so in external sensory processing (“How far away is that pedestrian?”). “Whenever you pay attention to the outside world, its activity decreases,” said Parvizi.

To learn what specific parts of this region are doing during, say, recall versus arithmetic requires more-individualized anatomical resolution than an fMRI provides. Otherwise, Parvizi said, “if some nerve-cell populations become less active and others more active, it all washes out, and you see no net change.” So you miss what’s really going on.

For this study, the Stanford scientists employed a highly sensitive technique to demonstrate that introspective and externally focused cognitive tasks directly interfere with one another, because they impose opposite requirements on the same brain circuitry.

The researchers took advantage of a procedure performed on patients who were being evaluated for brain surgery at the Stanford Epilepsy Monitoring Unit, associated with Stanford University Medical Center. These patients were unresponsive to drug therapy and, as a result, suffered continuing seizures. The procedure involves temporarily removing small sections of a patient’s skull, placing a thin plastic film containing electrodes onto the surface of the brain near the suspected point of origin of that patient’s seizure (the location is unique to each patient), and then monitoring electrical activity in that region for five to seven days—all of it spent in a hospital bed. Once the epilepsy team identifies the point of origin of any seizures that occurred during that time, surgeons can precisely excise a small piece of tissue at that position, effectively breaking the vicious cycle of brain-wave amplification that is a seizure.

Implanting these electrode packets doesn’t mean piercing the brain or individual cells within it. “Each electrode picks up activity from about a half-million nerve cells,” Parvizi said. “It’s more like dotting the ceiling of a big room, filled with a lot of people talking, with multiple microphones. We’re listening to the buzz in the room, not individual conversations. Each microphone picks up the buzz from a different bunch of partiers. Some groups are more excited and talking more loudly than others.”

The experimenters found eight patients whose seizures were believed to be originating somewhere near the brain’s midline and who, therefore, had had electrode packets placed in the crevasse dividing the hemispheres. (The brain’s two hemispheres are spaced far enough apart to slip an electrode packet between them without incurring damage.)

The researchers got permission from these eight patients to bring in laptop computers and put the volunteers through a battery of simple tasks requiring modest intellectual effort. “It can be boring to lie in bed waiting seven days for a seizure to come,” said Foster. “Our studies helped them pass the time.” The sessions lasted about an hour.

On the laptop would appear a series of true/false statements falling into one of four categories. Three categories were self-referential, albeit with varying degrees of specificity. Most specific was so-called “autobiographical episodic memory,” an example of which might be: “I drank coffee yesterday.” The next category of statements was more generic: “I eat a lot of fruit.” The most abstract category, “self-judgment,” comprised sentences along the lines of: “I am honest.”

A fourth category differed from the first three in that it consisted of arithmetical equations such as: 67 + 6 = 75. Evaluating such a statement’s truth required no introspection but, instead, an outward, more sensory orientation.

For each item, patients were instructed to press “1” if a statement was true, “2” if it was false.

Significant portions of the PMC that were “tapped” by electrodes became activated during self-episodic memory processing, confirming the PMC’s strong role in recall of one’s past experiences. Interestingly, true/false statements involving less specifically narrative recall—such as, “I eat a lot of fruit”—induced relatively little activity. “Self-judgment” statements—such as, “I am attractive”—elicited none at all. Moreover, whether a volunteer judged a statement to be true or false made no difference with respect to the intensity, location or duration of electrical activity in activated PMC circuits.

This suggests, both Parvizi and Foster said, that the PMC is not the brain’s “center of self-consciousness” as some have proposed, but is more specifically engaged in constructing autobiographical narrative scenes, as occurs in recall or imagination.

Foster, Dastjerdi and Parvizi also found that the PMC circuitry activated by a recall task took close to a half-second to fire up, ruling out the possibility that this circuitry’s true role was in reading or making sense of the sentence on the screen. (These two activities are typically completed within the first one-fifth of a second or so.) Once activated, these circuits remained active for a full second.

Yet all the electrodes that lit up during the self-episodic condition were conspicuously deactivated during arithmetic calculation. In fact, the circuits being monitored by these electrodes were not merely passively silent, but actively suppressed, said Parvizi. “The more a circuit is activated during autobiographical recall, the more it is suppressed during math. It’s essentially impossible to do both at once.”

Reference:

The above story is reprinted from materials provided by Stanford University Medical Center, via MedicalXpress.

Journal: Proceedings of the National Academy of Sciences

Brain Waves

February 10, 2012 3 comments

Introduction Brain waves

The brain generates tiny electrical pulses as The brain produces four main waves with thoughts traverse the labyrinth of the mind. The specific frequencies:

physical conduits of these thoughts are the millions of nerve cells or neurons in the brain. Just as radio signals, in order to make a comprehensible message, are beamed out on radio waves, a band of signals within a defined frequency, so the brain’s activity also occurs in waves. Brain waves can be measured on an electro-encephalograph machine (which is normally abbreviated to EEG Machine). By attaching sensitive electrodes to the scalp, it is possible to measure accurately the type of brain wave that a subject is producing. These waves are usually expressed in the number of cycles per second (CPS) or with their frequency (Hz).

1. Beta level brain waves – range 12-16 Hz (also 13-25 Hz)

2. Alpha level brain waves – range 8-12 Hz 3. Theta level brain waves – range 4-7 Hz
4. Delta level brain waves – range 0.5-3 Hz

The following chart relates each type of brain wave to its principal function. We must remember however, that when we speak of someone being ‘in alpha’ we mean that this is their characteristic and predominant brain wave. Other brain waves will also be present, but in smaller quantities than usual.

Brain activities

The linking of left and right brain activities is important in producing a shift from learning to accelerated learning. Yet our society is very ‘beta orientated’. We are busy thinking about the problem in hand, but don’t leave ourselves sufficiently open to other influences, which would help us memorize faster and make the sort of less expected connections that we call creative thinking.

Beta brain

In beta you don’t see the wood for concentrating on the trees. But learn to relax, increase the proportion of the alpha and ideally theta brain waves, and you have created the conditions where you may begin to see the whole picture.

Alpha brain

‘Alpha’ is a natural and receptive state of mind, that we can all attain through the techniques of relaxation. They principally involve simple and pleasant relaxation exercises and listening to certain types of music.

Theta brain

The theta brain wave pattern is especially interesting. It occurs spontaneously to most of us in the twilight state between being fully awake and falling asleep. Arthur Koestler called it ‘reverie’. This drowsy stage is associated with fleeting semi-hallucinatory images. Thousands of artistic and literary inspirations and scientific inventions have been credited to this state, a sort of freeform thinking that puts you in touch with your subconscious.

Brain waves interpretation

Many psychologists would agree it is a reasonable hypothesis that, when left/right brain symbiosis takes place, conscious and subconscious are also united. The proportion of theta brain waves becomes much higher than normal. This is the moment when logical left brain activity declines. The left brain, which normally acts as a filter or censor to the subconscious, drops its guard, and allows the more intuitive, emotional and creative depths of the right brain to become increasingly influential.

If the hypothesis is true, then do women, popularly characterised as more intuitive, reach a walking theta state more often than men; and can this be associated with the fact that their left/right brain link, the Corpus callosum, is larger and richer in connective capabilities than men’s? We do not yet know, but it is a fascinating area for future research.

At the University of Colorado Medical Centre and at the Biofeedback Centre in Denver, Dr. Thomas Budzyski has found that, when people were trained to achieve and maintain theta brain waves using biofeedback techniques, they did indeed learn much faster. Moreover, many emotional and attitudinal problems were solved at the same time.

To read more click on this link to the full article: Brain Waves (pdf).