Today, our brains age. The University of Houston's
College of Engineering presents this series about
the machines that make our civilization run, and
the people whose ingenuity created them.
Science
magazine writer Laura Helmuth describes new studies
of the way our brains age. Scientists have come up
with some surprises. We've known part of the story
for some time -- that brains cells die, for
example, and that certain brain centers shrink. The
volume of our hippocampus, which is crucial to
memory, shrinks about seven percent per decade
after we reach 45.
On average, our capacity for processing information
undergoes a fairly steady decline from age twenty
through eighty. However, the drop varies greatly
from person to person. Our knowledge and
understanding of words steadily
increases up to the age of seventy. Then
it begins dropping off only slightly. "That should
give comfort," Helmuth says, "to those who have
been trounced by a great-aunt in a game of
Scrabble."
So just what is the brain up to as we age?
Researchers have been running tests with
positron emission tomography. These
PET scans reveal what's happening in the
brain while subjects think. The result is
remarkable.
When a young person focuses upon, say, a verbal
puzzle, the left and right hemispheres both show
activity, but only for a moment. The young person
will quickly squelch right brain activity and focus
thought within the left brain. The old person no
longer does that. Instead, the older test-taker
continues using more than one portion of the brain.
This opens the way to different implications. It
might reflect a sort of floundering inefficiency in
the older person. But another factor emerges. The
fastest of the old people show the strongest
activity in the extra hemisphere. That suggests
that many older people have developed means for
calling in additional resources. It gives new
meaning to the old expression, ring wise.
Take the problem of recognizing faces: When elders
are called on to match faces, they often go to the
region of the brain that processes emotions.
Perhaps the older person uses the emotional content
of the face, the expression, in the
identification.
Helmuth ends by raising the old question of
wisdom. What about that mystic quality?
I'm still impatiently awaiting its arrival. And all
these tests, it turns out, tell us almost nothing
about wisdom. Helmuth says, "It's awfully tough to
find a quantitative measure, much less one that can
be assessed while the aged but wise recline in a
PET scanner." Still, it is clear that we old think
very differently now than we did fifty years ago.
Whether that's for better or worse, I am greatly
helped by something Wordsworth wrote,
The wiser mind
Mourns less for what age takes away
Than what it leaves behind
And often, glad no more,
We wear a face of joy because
We have been glad of yore.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Helmuth, L., A Generation Gap in Brain Activity.
Science, Vol. 296, June 21, 2002, pp
2131-2133.
Andreas Vesalius' Yorick-like image of the human
skull (or mind), contemplating the human mind, 1542
(about sixty years before Shakespeare wrote
Hamlet).
The Engines of Our Ingenuity is
Copyright © 1988-2002 by John H.
Lienhard.
