Monday, April 11, 2011


Brain: Hippocampus
The hippocampus is located in the medial temporal lobe of the brain. In this lateral view of the human brain, the frontal lobe is at left, the occipital lobe at right, and the temporal and parietal lobes have largely been removed to reveal the hippocampus underneath.

It’s hard to deny that we live in a stressful society. Many of us are busy from the instant we wake up to the moment we fall asleep, taking care of children, commuting to and from work, putting in a solid eight to twelve hours at the office, keeping up with our reading and e-mail and phone correspondence, and then having to confront 100-odd cable TV channels.

The human response to stress—an increase in heart rate, blood pressure, breathing, metabolism, and blood flow to muscles—has evolved over millions of years and is responsible, in no small measure, for the survival of our species. It also contributes to peak performance under pressure—an asset to athletes, firefighters, and countless others. But the inappropriate activation of the stress response, in a world where people rarely face life-or-death situations, can eventually damage both the heart and the brain.

Researchers have examined how stress affects people in various ways. As one example, in a five-year study published in 1998, psychologists gave memory tests to people in their 70s and asked them to find their way through different mazes. The subjects who did the worst on the tests had the highest levels of cortisol, a stress hormone in the glucocorticoid family. Over the years these same people had lost the most brain cells from the hippocampus, a brain structure critical for memory.

Some studies imply that there is a link between a shrinking hippocampus, and chronic exposure to glucocorticoids like cortisol. We see this most clearly in an extreme condition called Cushing’s syndrome, in which the adrenal glands release large quantities of glucocorticoids.

This condition is accompanied by memory problems known as Cushingoid dementia. MRI brain scans performed at the University of Michigan showed that the hippocampus shrinks in Cushing’s patients. People who secreted the most glucocorticoids suffered the most serious memory problems and the worst hippocampal atrophy.

However, other studies question whether the glucocorticoids alone are responsible for the degeneration of hippocampal neurons. A 1999 study performed at the University of Washington exposed aging rats to elevated glucocorticoid concentrations for 12 months without increasing their exposure to stress.

The average size of the hippocampus in these rats, as well as the number and density of neurons in that region, remained the same as in an unexposed control group. Hippocampal damage, the researchers concluded, must arise from other effects of stress, perhaps in conjunction with elevated glucocorticoid levels but not due only to them. These results hint that the organic effects of stress on the brain are complex and unlikely to yield to a simple remedy.

Unfortunately, stress is not the only thing we have to worry about. Research at Washington University School of Medicine in St. Louis shows that chronic depression can also harm the hippocampus.

In a 1999 study, investigators scanned the brains of 48 women, ranging from age 23 to 86. In women who had a history of depression, the size of the hippocampus was 9 percent to 13 percent smaller. The hippocampal volumes were smaller in women who had been depressed more often, but age was not a factor. Glucocorticoids may be involved here, too, as depressed patients produce abnormally high quantities of this stress hormone.

Fortunately, there are techniques for managing stress. Physical conditioning can help by lowering your blood pressure, and resting heart rate. Exercise—such as aerobic workouts and competitive sports—can also provide an outlet for relieving some of the stress and frustration that build up in a day. Some people achieve deep relaxation through contemplative activities like yoga and meditation, while others may prefer listening to Mozart or wild dancing.

People who handle stress well generally have strong social ties with others.
Whenever possible, they avoid putting themselves in situations in which they feel helpless, buffeted by forces beyond their control. However, when things don’t go their way, they try to take it in stride.

Tags:Stress management techniques

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