-
- "When I was younger, I could remember
anything, whether it had happened or not; but my faculties are decaying
now and soon I shall be so I cannot remember any but the things that never
happened. It is sad to go to pieces like this but we all have to do it."
-- Mark Twain
-
- Mark Twain was not the first person to
recognize the propensity of old folks to clearly recall things that never
happened, but new research from Washington University in St. Louis is providing
still more evidence that Twain based his satire on a keen understanding
of the human condition.
-
- "Our study reaffirms what Mark Twain
said years ago -- older adults do appear more likely to remember things
that never happened," said David Balota, Ph.D., lead author of the
study and a professor of psychology in Arts and Sciences at Washington
University.
-
- "It is sad, as Twain said, when
our memories 'go to pieces,' but Twain may have been wrong when he said
that we all have to do it," Balota said. "Our studies and other
ongoing research in the field are beginning to provide important clues
about the processes that lead to memory loss in both normal aging and in
Alzheimer's, and about which specific aspects of memory are prone to breakdowns
and which seem to remain intact."
-
- In an invited address June 5, 1999, at
the American Psychological Society meeting in Denver, Balota will argue
that this study provides further compelling evidence in support of a relatively
novel approach to understanding how Alzheimer's cripples the human mind.
-
- "These findings suggest that the
cognitive problems associated with Alzheimer's might be better conceptualized
as a breakdown in attention rather than primarily a breakdown in memory
in the classical sense," Balota said.
-
- "Our results are quite consistent
with recent neuropathological evidence linking Alzheimer's disease to physical
breakdowns in the frontal lobes, where much of the mind's strategic information
processing, including attention functions, are believed to be in part coordinated.
Taken together, these studies provide evidence for an attention-based model
of Alzheimer's disease."
-
- The study, which is supported by a grant
from the National Institute on Aging, is in press for publication in a
forthcoming issue of the journal Cognitive Neuropsychology. Other authors
on the study are Michael J. Cortese, Janet M. Duchek, David Adams, Henry
L. Roediger III, Kathleen B. McDermott and Benjamin E. Yerys, all of Washington
University in St. Louis.
-
- It's no secret that older adults often
express frustration at their increasing inability to recall seemingly simple
things, but this study suggests that older people -- and to a much greater
extent those individuals struggling with Alzheimer's -- should also be
somewhat skeptical about the accuracy of even those things that they think
they remember quite well.
-
- "Our findings, along with other
studies, demonstrate that older people are very susceptible to the creation
of false memories," Balota said, "which is interesting because
it suggests that memory problems associated with aging are not the result
of a broad general decline in all memory-related functions, but are due
to sharp declines in some cognitive areas, specifically portions of the
brain that control the strategic processing of information once it is recalled
from memory."
-
- Testing memory
-
- Balota's study is based on an analysis
of false recall and recognition rates among 159 individuals who were divided
into five groups: healthy college students, healthy older adults about
age 70, healthy old-old adults about age 85; and two groups of older adults
with either very mild or mild symptoms of Alzheimer's related dementia,
who volunteered to participate in studies at Washington University's Alzheimer's
Disease Research Center.
-
- Subjects were read a list of 12 associated
words that strongly suggest another non-presented critical target word,
and later asked to recall words on the list. Imagine being read a list
of words, such as Bed, Rest, Awake, Tired, Dream, Wake, Snooze, Blanket,
Doze, Slumber, Snore, Nap. Although the word Sleep was never presented,
research demonstrates that many people will later recall the word and appear
to believe incorrectly that it was indeed presented as part of the list.
-
- Such lists of semantically associated
words, first developed in 1959 by James Deese, have recently become a popular
and powerful paradigm for the study of memory function. By applying the
simple word recall tests to various groups of individuals under various
constraints and conditions, researchers are slowly unravelling important
details about human memory function.
-
- Balota's studies indicated that young
adults recalled the presented words about 70 percent of the time, but mistakenly
recalled the non-presented word in about 30 percent of the trials. Whereas,
healthy older adults recalled the presented words about 55 percent of the
time, and the non-presented words about 37 percent of the time. And people
with mild Alzheimer's related dementia actually recalled the item that
was not presented slightly more often (35 percent) than they recalled words
that were actually presented (only 32 percent).
-
- Results from the study are shedding light
on one of the most salient problems in Alzheimer's research -- how the
disease influences a person's ability to acquire and retrieve new memories.
A key to understanding the memory process is knowing that memories are
never generated as 100 percent accurate, vivid snapshots of past events
and experiences, rather they are constructed from various tidbits of related
information that the mind is able to retrieve and assimilate.
-
- Memories of events, experiences and other
knowledge-based information are stored in intricate webs linked by logical,
semantic associations; a thought or other stimulus can spark a reaction
along these networks and cause a flood of information to be activated.
Higher strategic processing skills are then required to sort through these
jumbled recollections and associations, discarding those that seem out
of touch with reality and focusing on those that most meet the needs of
the current task at hand.
-
- Current models in experimental psychology
emphasize the importance of a particular strategic information processing
function -- attentional control systems -- in both the encoding and retrieval
of information in memory. These attentional systems, Balota explains, allow
a person to keep focused on a particular topic (the understanding of this
text, for example) while inhibiting irrelevant information that is also
impinging on the senses (the way in which your third toe feels on your
left foot, which is also providing a signal to the brain but is not consciously
apprehended until you select that pathway).
-
- The ability to maintain attention to
the mental task at hand is critical to the memory retrieval process because
the mind must constantly weigh and choose among various streams of potentially
relevant information that flood into the conscious mind from the memory
network. For instance, the ability to retrieve useful information about
"organs" during the following sentence "The musician was
pleased to hear about the sale of pianos and organs at the music store"
requires that the mind be able to quickly recognize and discard tangentially
related information, such as information about "organs" of the
human body.
-
- Attention breakdown
-
- The notion now being put forth by Balota
and other Alzheimer's researchers is that the underlying structure of the
knowledge-based memory system remains relatively intact, at least during
early stages of Alzheimer's, while critical strategic information processing
systems in the brain's frontal lobe begin to break down. The loss of these
strategic information processing skills, such as the ability to maintain
attention on the memory task at hand, makes it increasingly difficult for
the brain to accurately processs and assimilate the information it initially
set out to retrieve.
-
- The increase in false memory susceptibility
among healthy older adults and individuals with Alzheimer's seems to indicate
that the mind is somehow overwhelmed by the flood of jumbled recollections
still pouring in from an active network of knowledge-based associations.
False memories result not from a lack of information, but from the mind's
diminished ability to process the information and reach sound conclusions.
-
- "Recent studies in our laboratory
indicate that attentional control breakdowns can indeed provide a coherent
famework to interpret both the attention breakdowns and the memory breakdowns
that occur in Alzheimer's disease," Balota said. "It is quite
possible that the apparent memory loss in Alzheimer's disease is in fact
a breakdown in attention, as opposed to a breakdown in memory, as one finds
in classic cases of amnesia.
-
- "If indeed at least some of the
breakdowns may be due to strategic failures," Balota continued, "then
it is possible that more appropriate strategies may be trained in these
individuals and this may help reduce some of the cognitive declines that
occur in both healthy older adults and in early stage Alzheimer's disease.
For example, if there is a better understanding of the manner in which
such false memories are produced, maybe these individuals could be trained
to avoid such distortions of memory. The critical first step is to determine
which systems breakdown and which systems are relatively preserved in these
populations."
-
-
- Editor's Note: The original news release
can be found at http://news-info.wustl.edu/feature/1999/May99-alzheimer.html
Note: This story has been adapted from a news release issued by Washington
University In St. Louis for journalists and other members of the public.
If you wish to quote from any part of this story, please credit Washington
University In St. Louis as the original source. You may also wish to
include the following link in any citation: <http://www.sciencedaily.com/releases/1999/06/990607072023.htmhttp://www.scien
cedaily.com/releases/1999/06/990607072023.htm
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