The Aging Brain: Attitude Counts!
While the teenage brain faces its share of challenges as it weathers the storm of adolescence, aging undoubtedly poses the greatest challenge to the normal life cycle of the brain. But contrary to popular belief, the slow march of mental decline many people associate with aging is not inevitable. While many people do experience memory lapses as they age, even as early as their 40s, this too is not preordained. Scientists who study the aging brain have identified an intriguing set of circumstances and personal attributes that seem to protect some people from the age-related declines in mental ability that so many aging Americans fear. In fact, brain research is turning up a surprising amount of evidence that, when it comes to maintaining mental sharpness into old age, attitude counts.
Marilyn Albert, Ph.D., a neuropsychologist at Johns Hopkins University School of Medicine, and her colleagues have been following a large group of "high-functioning" elderly people in an effort to determine what specific attributes tend to characterize people who maintain high levels of mental abilities into their 70s and beyond. Moderate to strenuous physical activity and higher levels of formal education have been found to be key predictors of cognitive maintenance. But perhaps the most surprising correlate with successful aging is a psychosocial factor that scientists call "self-efficacy."
Dr. Albert defines self-efficacy as "the feeling that what you do makes a difference in the things that happen to you every day. It boils down to feelings of control." Scientists have theorized that our self-efficacy beliefs influence the types of activities we pursue, as well as how much effort we put into them, and how persistent we are if the task proves difficult. If we have doubts about our ability to accomplish something, we may be less likely to try it, or may give up more easily. A cycle ensues: If we fail to engage in challenging activities, our risk for cognitive decline increases as we age. We might be anxious or stressed about what we can no longer do, which sets off a cascade of stress hormones that can themselves contribute to memory lapses, and may damage brain systems in other ways as well. Scientists say that taking steps to assert control over one's life and surroundings, even in seemingly small ways, may help us to maintain our mental faculties well into old age.
According to Dr. Albert, specific activities that may help maintain memory and cognitive function in elderly people include mental excercises like word puzzles and games as well as physical excercises like walking long distances, climbing stairs, and lifting objects. Social stimulation appears to be important, too. Controlling weight, lowering cholesterol, and avoiding smoking are all associated with less disease of the blood vessels of both the heart and the brain.
Genetics and Stem-Cell Research: Breathtaking Vistas on the Great Biological Frontier
With all the advances neuroscience has seen in the past decades, the future holds even greater promise. New techniques in cellular, molecular, and genetic biology are opening up vast opportunities for scientists to explore.
Two major scientific accomplishments have recently focused public attention in these areas: the near complete sequencing and mapping of the human genome and discoveries related to stem cells, found in both human embryos and in adults.
The mapping and sequencing of the human genome, completed in 2003, is the crowning achievement of nearly two decades of effort by dozens of research laboratories. This identification of the makeup of the human genome basically provides the blueprint of the human body, with the 23 pairs of chromosomes and roughly 30,000 genes found in each of the approximately 100 trillion cells in the human body. Some researchers estimate that half of all human genes and the multiple proteins they produce play a role in developing and maintaining the central nervous system (the brain and spinal cord). (See Chapter 2 for a more in-depth look at genes and the brain.)
Having access to the human genome sequences will help brain researchers in four areas: helping brain medicine diagnose disease, determining genetic versus environmental effects, deciphering the underlying mechanisms of disease, and developing effective medications and treatments.
Our understanding of the role of human DNA increased even more just recently. Neuroscientist Thomas Insel, Ph.D., of the National Institute of Mental Health, says, "The good news is that we have extraordinary new tools and technologies with which to addressurgent public health challenges." The Human Genome Project provided a consensus map of human DNA but it failed to describe variation. "Because variation is the key to understanding individual vulnerability and resistance to disease as well as human diversity, a map of human DNA variation may be even more informative than the original consensus map. [The year 2006] marks the completion of the 'HapMap' project, the first comprehensive map of human haplotypes."
With the HapMap, scientists will begin to learn how genes vary in the population. The question of how individual variations in DNA sequences are associated with risks for diseases can now be answered not only for single gene disease (such as Huntington's disease) but also for complex genetic diseases that affect the brain and the nervous system.
Another major development in cellular biology has come in discoveries related to stem cells. Stem cells are "blank," undifferentiated cells that can grow into heart cells, kidney cells, or other cells of the body. Originally thought to be found only in embryos, stem cells have unexpectedly been discovered in adult brains and other parts of the body.
In experiments, researchers have shown that stem cells can be transplanted into various regions of the brain, where they develop into both neurons and glia. Moreover, researchers now believe that other types of stem cells-from bone marrow, muscle, or skin-can be made to differentiate into neurons (and even neurons of specific types) when grown in culture and treated with appropriate inducing factors.
The potential use of such stem cells for the treatment of neurodegenerative disorders such as Parkinson's disease and to replace damaged neural tissue could provide a whole new dimension to research and ultimately to treatment of some of our most difficult brain diseases and disorders. (For a more in-depth look at stem cell research, turn to p. 23.)As scientists learn more about cellular and genetic biology, they are discovering new keys that may unlock the mysteries of the devastating brain disorders that continue to ravage mankind. A large group of leading brain scientists from around the world has outlined specific areas of neuroscience in which rapid advances are forecast. Already, progress has been made in each of these areas. True breakthroughs that will change the way we think about the brain and its disorders are imminent
الإثنين يناير 12, 2015 2:09 am من طرف نبراس جميل
موضوع: the aging brain 
