The birth of brain cells

what you need to know  about neurogenesis

Neurogenesis

We've all heard the warnings: If you (fill in the blank) you'll kill brain cells. And because scientists believed until very recently that you were born with all the brain cells you'd ever have, that was a fairly dire warning. You broke it, and you were stuck with the results.

 Recently we've been able to relax a bit, because we know that our brain makes new cells in at least two sections: the detente Cyrus of the hippocampus, a structure involved in learning and memory, and the olefactory bulbs. And it may in fact create new neurons elsewhere in the brain; we don't know for certain yet.

 Most of this research has been done on animals, but some human studies have confirmed the finding. Studies were done on terminal cancer patients who generously agreed to be injected with a marker for new cell production and to offer their brains for study after their death. The autopsies showed that even in the face of aging and death, their brains continued to produce new neurons to the very end. Chemotherapy could give us an idea of what happens when we don't make new neurons. Chemotherapy impairs the cell division needed for making new cells, and people who have had chemotherapy treatment for cancer and some other serious diseases often complain about a syndrome sometimes referred to as chemobrain. They have trouble with the kinds of learning and remembering that everyone finds challenging, such as juggling multiple projects while trying to process new information. 

Because having a ready supply of new neurons on tap could help to keep your brain intellectually limber, scientists are looking for ways to exploit this to prevent or treat disorders that bring about cognitive decline. Meanwhile, they've found that these new brain cells disappear if you don't use them.

what to need to know about neuroplasticity

neuroplasticity 

 Scientists have long known that the brain can change itself. In fact, your brain is probably changing every microsecond in response to experiences, both external and internal. Those changes come mainly from the growth of new connections and networks among neurons, particularly among newborn neurons.

 We've known that different kinds of experiences lead to changes in brain structure, with more activity in the networks used most. In musicians, for example, the parts of the brain ddclicated to playing their instruments are disproportionately larger than in nonmusicians or in musicians who play a different instrument. A decade-old study of London taxi drivers skilled at navigation in the city center showed the same effect: they had larger hippocampi than nondrivers, reflecting the huge amount of data they needed to have at hand. Moreover, the longer they drove complicated routes around the city, the larger their hippocampi grew.

 Also, brains apparently riddled with blank areas or plaque and other signs of Alzheimer's disease have come from people functioning very well into late old age. Indeed, some brains lacking a hemisphere—the entire half of a brain—can function quite well.

 We also know the brain can sometimes repair itself after devastating injury, bypassing dead areas to create new connections. ABC news correspondent Bob Woodruff, critically injured by a roadside bomb in 2006 while covering the war in Iraq, suffered a brain injury so severe that part of his skull was permanently removed, and he was kept in a medically induced coma for more than a month. Few believed he would walk again, let alone work as a reporter. After more than a year of intensive therapy, which included relearning speech to

what is important or reasons to take care of human brain

 Centenarians—individuals one hundred years or older—are the fastest growing age group in the United States, and experts predict there may be as many as 1 million by 2050.

 If you're sixty years old (or younger) today, you could be in that group. And if you want your mind to be there along with you, take good care of your brain.

 You'll have plenty of company near your age: people aged eighty and older are the fastest-growing portion of the total population in many countries. By 2040, the number of people sixty-five or older worldwide will hit 1.3 billion, according to the National Institute on Aging, which announced the figures. And within ten years, there will be more people aged sixty-five and older than children under five in the world for the first time in human history.

 The most rapid increase will be in developing countries. By 2040, they will be home to more than 1 billion people aged sixty-five and over-76 percent of the projected world total. If you reach one hundred years, you are sure to live in interesting times, an old blessing (or curse) of the Chinese (who, incidentally, will have the world's largest population of elders by 2040). This global aging will change the social and economic nature of the planet and present some difficult challenges. Interesting times, indeed.

overcome aphasia, he made a hard-hitting documentary about the plight of injured soldiers and the deficits in government care. And then he went back to work as a reporter—in Iraq. Certainly Woodruff benefited from the kind of very expensive and intense treatment not available to all of us. Nevertheless, his recovery shows how remarkably able the brain is, especially because his was not a young brain: he was forty-four at the time of his injury. What we did not know for certain until recently is that what you think and feel also physically change your brain, such as intellectual

challenges, deliberate brain training, anxiety, and joy. So it seems there is a biological basis to mind training: you can learn skills aimed at changing your brain just as you learn repeated activities to change your body. Meditation is a brain-changing example. Studies show that regular practice of meditation results in physical as well as mental and emotional changes. In long-time practitioners of meditation, the two hemispheres become more balanced, the trigger-happy amygdala shows less reaction to emotional sounds, and the many brain regions involved in focused attention show greater activity (see "Boosting Your Brain with Meditation," p. 31).

How to changes in human brain 

Epigenetics 

Scientists are finding one of the ways your brain changes itself is by actually changing your genes—or more correctly, by the acting out (or not) of certain genes—in the process of epigenesis. We know that your genome is the total deoxyribonucleic acid (DNA) that you inherit from your ancestors and contains the instructions for making your unique body and brain. Another layer of information, called the epigenome, is stored in the proteins and chemicals that surround and stick to the DNA. It's a kind of chemical switch that determines which genes are activated (or not): it tells your genes what to do and where and when.

Researchers have discovered that the epigenome can be affected by many things, from aging and diet to environmental toxins to even what you think and feel. This means that even your experiences can literally change your mind by chemically coating the DNA that con
trols a function. The coating doesn't alter the underlying genetic code; rather, it alters specific gene expression, shutting down or revving up the production of proteins that affect your mental state.

 Epigenetics helps explain the gap between nature and nurture that has long puzzled scientists: why some illnesses and traits pop up in one but not both identical twins who have the same DNA, or why these traits skip a generation. It also helps explain neuroplasticity.

One researcher describes DNA as a computer hard disk, with certain areas that are password protected and others that are open. Epigenetics is the programming that accesses that material, writes Jolt Walter of Saarland, Germany, on the Web site Epigenome. 

Epigenetics can profoundly affect your health and, it seems, your happiness, changing not only your vulnerability to some diseases such as cancer but also your mental health. Scientists have found, for example, that a mother rat's nurturing, through licking and loving behavior that boosts the expression of a gene that eases anxiety and stress, bolsters emotional resilience in her newborn pups. They've also found that distressing events can turn off the expression of genes for brain cell growth protein and thereby trigger depression, and that epigenetic changes may also underlie the pathology of schizophrenia, suicide, depression, and drug addiction. 

The acting-out process of changeable genes—gene expression—is quite complicated and a new area of intense research. Just recently biologists have found that epigenetic changes may be heritable—passed on to your descendants—just as your DNA is. They have also found that altering gene expression with drugs or environments that provide more intellectual stimulation can improve learning and memory in cognitively impaired animals. Future therapies for memory disorders in humans might work in a similar way. It's a promising area with much to be learned. In 2008, the National Institutes of Health invested $190 million in the five-year Roadmap Epigenomics Program to pursue some of these promising fields of research.