delanceyplace.com 2/11/10 - new brain cells

In today's encore excerpt - the brain can grow
new neurons, but these disappear unless cognitively
challenged:

"Fresh neurons arise in the brain every day. ... Recent
work, albeit mostly in rats, indicates that learning
enhances the survival of new neurons in the adult
brain, and the more engaging and challenging the
problem, the greater the number of neurons that stick
around. These neurons are then presumably
available to aid in situations that tax the mind. It
seems, then, that a mental workout can buff up the
brain, much as physical exercise builds up the
body. ...

"In the 1990s scientists rocked the field of
neurobiology with the startling news that the mature
mammalian brain is capable of sprouting new
neurons. Biologists had long believed that this talent
for neurogenesis was reserved for young, developing
minds and was lost with age. But in the early part of
the decade Elizabeth Gould, then at the Rockefeller
University, demonstrated that new cells arise in the
adult brain - particularly in a region called the
hippocampus, which is involved in learning and
memory. ...

"Studies indicate that in rats, between 5,000 and
10,000 new neurons arise in the hippocampus every
day. (Although the human hippocampus also
welcomes new neurons, we do not know how many.)
The cells are not generated like clockwork, however.
Instead their production can be influenced by a
number of different environmental factors. For
example, alcohol consumption has been shown to
retard the generation of new brain cells. And their birth
rate can be enhanced by exercise. Rats and mice that
log time on a running wheel can kick out twice as
many new cells as mice that lead a more sedentary
life. ...

"Exercise and other actions may help produce extra
brain cells. But those new recruits do not necessarily
stick around. Many if not most of them disappear
within just a few weeks of arising. Of course, most
cells in the body do not survive indefinitely. So the fact
that these cells die is, in itself, not shocking. But their
quick demise is a bit of a puzzler. Why would the brain
go through the trouble of producing new cells only to
have them disappear rapidly?

"From our work in rats, the answer seems to be: they
are made 'just in case.' If the animals are cognitively
challenged, the cells will linger. If not, they will fade
away."

Tracey J. Shors, "Saving New Brain Cells,"
Scientific American, March 2009, pp. 47-48.