Amnesia

November 5, 2009 by · Leave a Comment 

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Amnesia refers to the loss of memory. Memory loss may result from two-sided (bilateral) damage to parts ofthe brain vital for memory storage, processing, or recall (the limbic system, including the hippocampus in the medial temporal lobe).

Amnesia can be a symptom of several neurodegenerative diseases; however, people whose primary symptom is memory loss (amnesiacs), typically remain lucid and retain their sense of self. They may even be aware that they suffer from a memory disorder.

People who experience amnesia have been instrumental in helping brain researchers determine how the brain processes memory. Until the early 1970s, researchers viewed memory as a single entity. Memory of new experiences, motor skills, past events, and previous conditioning were grouped together in one system that relied on a specific area of the brain.

If all memory were stored in the same way, it would be reasonable to deduce that damage to the specific brain area would cause complete memory loss. However, studies of amnesiacs counter that theory. Such research demonstrates that the brain has multiple systems for processing, storing, and drawing on memory.

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Fasting Good for Brain?

September 3, 2009 by · 1 Comment 

By Andrea Useem

2009-09-02T125425Z_01_DHA004_RTRMDNP_3_BANGLADESH-RAMADAN Ramadan is in its third week now, and the required dawn-to-dusk fasting often feels like a daily mini–marathon. By late afternoon, hunger and thirst have sucked me dry, leaving me sleepy, slow-minded, and sometimes short-tempered.

I know that the purpose of fasting is spiritual—God will reward us in the next life—but in this lifetime, fasting sometimes makes me an ineffective, irritable person. So I was excited to learn that Harvard psychiatrist John Ratey, MD, had spoken at a recent Renaissance Weekend event about how caloric restriction can improve brain function.

I emailed Dr. Ratey to find out if those benefits might extend to religious fasting, and he sent me a 2006 paper on the brain functioning of men during the Ramadan fast. The researchers studied a small group of healthy men during and after the holy month, looking at their brain activity via functional magnetic resonance imaging (fMRI). They concluded that “all individual results showed consistent and significant increase of activity in the motor cortex during fasting.”

That research builds on the work of other scientists, including Mark Mattson, PhD, who heads a neuroscience lab at the NIH’s National Institute on Aging. Mattson has done important research on how dietary restrictions can significantly protect the brain from degenerative diseases like Alzheimer’s or Parkinson’s.

In 2003, Mattson and others reported that rats deprived of food every other day, or restricted to a diet at 30% to 50% of normal calorie levels, showed not only decreased heart rates and blood pressure, but also “younger” brains, with “numerous age-related changes in gene expression.”

Mattson and his colleagues also shared data from research on humans, which shows that populations with higher caloric intakes—such as the United States and Europe—have a greater prevalence of Alzheimer’s than do populations that eat less—such as China and Japan. The authors speculate that humans may have adapted to conditions of feast and famine; the stress of having little food, they write, “may induce changes in gene expression that result in adaptive changes in cellular metabolism and the increased ability of the organism to reduce stress.”

Although this research is relatively new, with many questions left unanswered, the authors conclude that “it seems a safe bet that if people would incorporate a spartan approach to food intake into their lifestyles, this would greatly reduce the incidence of Alzheimer’s, Parkinson’s and stroke.” (Of course, how this recommendation translates for individual people remains almost a complete unknown; consult with your own doctor before restricting your diet in dramatic ways.)

But here’s the hard part: Although we know eating too much leads to all sorts of health problems, “it has proven very difficult to successfully implement prolonged dietary-restriction regimens,” reports Mattson and his team. Information and doctor’s orders are rarely enough motivation.

This last observation gave me hope, because it seemed the authors were overlooking the role of religion; it can inspire people in ways information or experts don’t. Would I be undergoing this rigorous month of fasting unless I believed strongly it was the right thing for me to do? Probably not. And the same goes for millions of Muslims around the world.

And many other religions include fasting or dietary restrictions as part of their religious observances. Members of the Church of Jesus Christ of Latter-Day Saints, or Mormons, for example, fast one Sunday a month. The Orthodox Church in America notes five separate fasting seasons on its website, in addition to individual fast days; during some of these fasts, all food is restricted, and during other fasts, only certain foods are off-limits. Some Roman Catholics abstain from meat on Fridays, and all do during Lent. Many types of Buddhist monks abide by a code that prohibits eating after noon each day.

Science may only now be discovering that some of these religious practices, both ancient and modern, offer nourishment not just for the soul, but for the body as well.

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Concussion

June 27, 2009 by · Leave a Comment 

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Concussion is a trauma-induced change in mental status, with confusion and amnesia, and with or without a brief loss of consciousness.

A concussion occurs when the head hits or is hit by an object, or when the brain is jarred against the skull, with sufficient force to cause temporary loss of function in the higher centers of the brain. The injured person may remain conscious or lose consciousness briefly, and is disoriented for some minutes after the blow. According to the Centers for Disease Control and Prevention, approximately 300,000 people have mild to moderate sports-related brain injuries each year, most of them young men between 16 and 25.

While concussion usually resolves on its own without lasting effect, it can set the stage for a much more serious condition. “Second impact syndrome” occurs when a person with a concussion, even a very mild one, suffers a second blow before fully recovering from the first. The brain swelling and increased intracranial pressure that can result is potentially fatal. More than 20 such cases have been reported since the syndrome was first described in 1984.

A state following injury in which there is temporary functional impairment without physical evidence of damage to the impaired tissues. The term usually refers to cerebral concussion produced by any type of trauma.

From a clinical point of view cerebral concussion is produced by a head injury which causes temporary unconsciousness but with complete recovery within 24 h. This temporary alteration is believed to result from one of several mechanisms. In all of these a sudden acceleration or deceleration appears to be aprerequisite. The sudden movement is thought to cause an unequal shifting of tissues of different specific gravities within the skull, between skull and brain, or between different brain tissues.

This word originally meant severe shaking, or the shock of an impact, but has come to mean the effect of such violence on the brain. The immediate effect of such an impact — usually when the moving head meets an immovable object, most commonly the ground — is unconsciousness. After a mild injury this lasts only a minute or so and the person is then dazed or confused for a few more minutes before recovering normal consciousness; occasionally recovery may take hours. After more severe impact injury, the patient may remain in coma for many days and remain confused for many more days thereafter. In either event there will be no memory for the moment of impact, often for a period immediately before this, and always for the period of unconsciousness and confusion: this is known as post-traumatic amnesia.

It is now recognized that the effect of the jelly-like brain being distorted by these forces is to stretch or even tear delicate nerve fibres, resulting in some permanent damage. After mild injury this is very limited, but after more severe impact there is more severe and more widespread damage to fibres. There can therefore be both mild and severe concussion.

After only mild concussion there are often symptoms for several days, sometimes weeks — headache, fatigue, dizziness, and poor concentration. In a few patients these post-concussional symptoms give rise to anxiety and other psychological symptoms that can aggravate and prolong the organically-impaired function that the patient suffers. In contact sports there is the risk of repeated concussions, and the small amount of damage sustained each time can be cumulative. Moreover, soon after one concussion the brain may be more susceptible to a second blow, and this is why most sports have rules about waiting 2-3 weeks before playing again, for example after concussion on the football field or in the boxing ring. The repeated concussions over a period of years that boxers can experience may result in progressive brain damage, evident in altered mental function and control of the limbs — the so-called ‘punch-drunk’ syndrome. This is now rare, as there are stringent regulations to limit exposure to such a hazard.

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