Most bodily organs continually die and regrow a little at a time. It takes two years, for example, for all the cells of the liver to be replaced by fresh ones. Research from Karolinska Institutet in Sweden now shows that there is one important exception to this the nerve cells of the brain remain the same throughout a person's life.

Many scientists have suspected that the cerebral nerve cells lack this renewal ability. However, studies on apes and rodents have indicated that brain cells can reform in mammals after all including man. One problem with these findings has been the research methodology, as the most common way of measuring the age of nerve cells is extremely complicated, especially in man, and gives unreliable and controversial results.

Last year, stem cell researcher Jonas Frisn from Karolinska Institutet presented a way to settle the issue with help from unexpected quarters the nuclear tests of the cold war. He used a variation on the well-known carbon-14 method that is based on the fact that atmospheric concentrations of C14 peaked sharply during the cold war tests. By comparing levels of C14 in plant and animal cells with atmospheric levels, it is possible to pinpoint the exact time the cells were born.

Jonas Frisn has now teamed up with another Swedish research group from Gteborg University, led by Dr. Peter Eriksson, and scientists from Australia and America to measure levels of C14 in neocortical nerve cells from all the cerebral lobes of adult individual brains. They have been able to show that levels of C14 in the nerve cells from all areas of the cerebral cortex were just as high as the atmospheric levels at the time of the individual's birth. Put another way, no cell division had taken place in the neocortex during the person's life from infancy to adulthood.

The researchers stress that the method has certain limitations. For instance, newly formed nerve cells might remain undetected if they have m
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Contact: Katarina Sternudd
katarina.sternudd@ki.se
46-852-483-895
Karolinska Institutet
11-Aug-2006