Hi all , found this in the NY Times ,
Is Memory Loss Inevitable? Maybe Not
By LINDA CARROLL
Ruth Arnold can recall a time when her memory was perfect.
Years
ago, working as a college reference librarian, she could put
her finger
on any piece of minutia at will. "I remembered all the books
and what
was in them," Mrs. Arnold said.
At the moment, it is still thought to be generally true that older
people do not
remember as well as younger people. Dr. Denise C. Park, a professor
of
psychology and a senior research scientist at the Institute for
Social Research
at the University of Michigan in Ann Arbor, says that when young
and old
people, ranging in age from 20 to 90, are asked to listen to a
series of
numbers and letters and then reverse the series, young people can
remember
and manipulate longer lists faster.
Older people also appear to have more attention problems. Dr.
Sandra
Weintraub, associate professor of psychiatry and neurology and
clinical core
director of the Alzheimer's Disease Center at Northwestern
University, found
a conspicuous different between older and younger people in a
driving
simulation experiment. The older group -- both those with good
memories
and those with early Alzheimer's -- were more easily distracted by
passing
objects and scenery than the younger group. But, studies have also
shown
that more than a third of the elderly can remember the names and
events in
their lives as sharply as their 20-year-old counterparts,
suggesting that
memory loss is not necessarily inevitable.
At research centers around the country, scientists are trying to
tease out the
underlying causes for non-Alzheimer's-related memory loss and,
ultimately,
to find a cure. In one lab, researchers have improved the memories
of older
mice by tweaking certain neurotransmitter levels.
In another lab, investigators studying the effects of stress on
memory have
found that the neurons needed for memory shrink in response to high
levels
of stress hormones. Long-term exposure to stress may lead to
permanent
changes in the brain, some experts think.
Still other researchers are studying identical and fraternal twins
to discover
whether some people are genetically programmed to become forgetful
with
old age. Early indications are that genes do play some role,
although experts
debate how important it is.
Ultimately, scientists may discover that age-related memory loss
may be a
result of a combination of bad genes and a hard life. "I think it's
a
nature-nurture interaction, in large part," said Dr. Bruce S.
McEwen,
professor and head of the laboratory for neuroendocrinology at
Rockefeller
University in New York. "A genetic vulnerability increases the
likelihood that
experience will have an effect."
Researchers only recently learned that "normal" age-related memory
loss
might involve a different part of the hippocampus, a small
structure in the
middle of the brain, than Alzheimer's disease.
Several decades ago, scientists learned that the hippocampus was
central to
learning and memory. In surgery to cure epilepsy, doctors removed
the
hippocampus from a man, curing him of seizures, but leaving him
unable to
store new memories.
It was equivalent to having no save function on a computer, said
Dr. Scott A.
Small, an assistant professor of neurology at the Columbia College
of
Physicians and Surgeons in New York. One has the information as
long as it
is on the screen, but once something new flashes on the monitor,
the old data
are lost.
"If you met this man at a dinner party, he would know who you were
as long
as his attention was focused on you," Dr. Small said. "If his
attention was
diverted in the middle of the conversation, he would look at you as
if he'd
never met you before."
Dr. Small and his colleagues have been using functional M.R.I., an
imaging
system sensitive to the activity of nerve cells, to get a closer
look at how
Alzheimer's disease and mild age-related memory loss affect the
brain. In one
experiment, the scientists put people into a functional M.R.I.
and then watched as neurons sparked in different regions of the
hippocampus
when the people remembered others' faces.
Scans from Alzheimer's patients showed next to no neuronal activity
in a
section of the hippocampus called the entorhinal cortex as well as
a variety of
other regions.
Studies have shown that the entorhinal cortex is the first area of
the
hippocampus to be damaged by Alzheimer's.
But, in people with mild memory loss, the results were different.
In 8 of 12
people, the entorhinal cortex flashed brightly, while another
region, called the
subiculum, also in the hippocampus, glowed dully. The other four
people had
less activity in the entorhinal cortex, but still more than those
with
Alzheimer's.
The researchers suspect that those four people may have early
Alzheimer's.
They will follow the 12 to see if it is possible to predict who is
at risk of
developing the disease.
Dr. Small and others suspect that the non-Alzheimer's related
deficits in
memory are a result of faulty wiring rather than actual nerve-cell
death.
Studies have shown that while the brain shrinks in size, the number
of cells
stays relatively constant. So, researchers now think that there is
either a
scarcity of certain crucial neurotransmitters or that receptors
designed to
take up these brain chemicals are malfunctioning.
Whether the cause of the wiring problem is genes or environment is
the
matter of some debate.
"This is the million dollar question," said Dr. Richard Mayeux, a
professor of
psychiatry and public health and director of the Taub Institute on
Alzheimer's
Disease and the Aging Brain at Columbia.
"There are suggestions from all over that mental function is a
heritable trait,
albeit a complex one."
For example, Dr. Mayeux said, studies that followed twins found
that even in
their 80's, identical pairs were often more similar with respect to
memory
than fraternal twins. "This doesn't mean that we will identify one
particular
gene that controls preservation of memory, but it really points to
memory
being a heritable trait," Dr. Mayeux said.
While allowing that heredity may play a role in memory loss, other
researchers have focused on a host of environmental factors,
including
stress, sex hormones and blood flow to the brain.
Large population studies have implicated stress in memory loss. A
10-year
MacArthur Foundation study found that "self-efficacy," along with
physical
and mental activity, predicted good memory in old age.
"What we called self-efficacy has to do with the control people
feel over their
lives, whether they feel they can do something to influence what
happens in
their daily lives,"' said Dr. Marilyn S. Albert, a professor of
psychiatry and
neurology at Harvard.
"This general feeling of control, we can think of as a sort of
anti-stress."
So far, laboratory researchers have looked only at the effects of
short-term
stress, which appear not to be permanent.
"In our animal model of stress, you can largely reverse the effects
of stress
as long as it hasn't gone on for a number of weeks," Dr. McEwen of
Rockefeller University said. "This is actually a gray area. We
don't know yet
how long it takes before you produce permanent brain damage."
But Dr. McEwen says the kinds of stresses generated by tight
deadlines and
high pressure jobs are probably not enough to seriously affect the
memory.
"More likely it's the kind of stress experienced by a person at the
low end of
the totem pole, in a meaningless job, in a lousy environment, with
bad
interpersonal relationships," Dr. McEwen said.
"It comes from a sense of hopelessness, helplessness, despair and
depression.'
Researchers have looked at other possible culprits to explain
age-related
memory loss. Studies of post-menopausal women have linked low
levels of
estrogen and testosterone to memory decline. Some think a byproduct
of
oxygen metabolism -- free radicals -- could be toxic to memory
brain cells.
Or the brain may simply be starving to death as blood supply from
the heart
decreases with age.
Some researchers, rather than looking for causes, are seeking
treatments. In
another Columbia laboratory, researchers are improving the memories
of
mice with injections of a drug similar to dopamine. If young mice
are put in a
maze several days in a row, most will learn where the escape route
is and go
right to it, said Dr. Eric L. Kandel, a professor at Columbia. If
middle-aged
mice, those 12 to 14 months old, are in the same maze for several
days,
fewer of them will remember how to negotiate their way out. But
when the
middle-aged mice are given the dopamine substitute, their memories
improve.
"It's not a fountain of youth, but it restored most of their
function," Dr.
Kandel said. "The idea that we will one day come up with a drug
that cures
all memory problems is a dream. I think it's a decade away, at
least."
Copyright 2000 The New York Times Company
--
Cheers,
Joao Paulo - Salvador,Bahia,Brazil
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