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Memory
and Memory Loss
by
Marilyn Aiello
Introduction-
Memory- Am I losing It?
Everyone is concerned about their memory as they age and start to forget
things more frequently. Dementia is one of the greatest fears of the senior
population. The probability of developing a form of dementia dramatically
increases as we age. The precise prevalence of dementia is unknown but is
estimated to be 15% of the population greater than age 65 and increasing at
about 1% per year to a projected 45% of the population at age 85 years. There
are many causes of dementia, but Alzheimer’s Disease (AD) is estimated to
account for over 50% of all cases. Dementia has probably existed for
centuries, but it was rare when Alois Alzheimer first reported it in 1907. At
this time the average life expectancy was only 50 years of age and only a few
people lived to their 6th or 7th decade. (Virginia Lee;
2000). Scientists estimate that
up to 4 million Americans currently suffer from Alzheimer’s Disease.
According to the U.S. Bureau of the Census, more than 34 million (13%)
Americans are over 65 years and this percentage will accelerate rapidly
beginning in 2011, when the first baby boomers reach age 65. Because of our
increased life expectancy, it is estimated that 18% of the population will be
older than 65 by the year 2025. (NIA; 1999)
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Memory-
How does it work in the brain?
The human brain is made up of billions of nerve cells called neurons that
communicate with each other via a large array of biological and chemical
signals. Each neuron has several parts and each part has a specific function.
Glial cells support and nourish the neurons.
Neurons
communicate with each other through small gaps called synapses using a
combination of electrical discharge and a secreted substance called a
neurochemical. Scientists estimate that each one of our neurons can have up to
15,000 synapses. There are several neurochemicals and each one can either
“turn on” or “turn off” a signal. Millions of signals travel back and
forth across the synapses in a fraction of a second at any given time.
(NIA;1999)
Neurons
are grouped and organized and have different jobs depending on their location
in the brain. The brain is divided into the right and left hemisphere and each
hemisphere is divided into 4 lobes called the frontal, temporal, occipital and
parietal lobes. The location of neurons responsible for memory are generally
wide spread. However, within the brain there is a “complex highly organized
filing system” for the retrieval of memory.
By
studying bizarre cases of memory difficulty, we can understand memory better.
For example, Dr. John Hart studied K.R., a librarian who could no longer name
animals or describe them. She could say, “parsley is green”, but could not
name the color of a frog. She could pick out the proper color for an elephant
from cue cards but could not say that an elephant was gray. This shows that
the description of animals in language
is stored in a different place in the brain than the knowledge of animals in vision.
So K.R. was able to visually recognize that an orange elephant is incorrect
because she could use her intact visual knowledge, but she could not say that
an elephant should be gray because her language system was partly cut off from
her visual system. In another case studied by Dr. Hart, a woman had lost her
ability to name small household appliances. She could name refrigerator and
stove but could not name iron or scissors. (Barry Gordon, 1995)
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What
are the Mechanics of Memory?
Before a memory can be retrieved, it must be registered or perceived and
stored properly. Deficits in any of these three areas may appear to memory
problems. However, if the item to be remembered does not register, we are
looking at comprehension, attention or sensory (hearing, visual) deficits,
rather than memory deficits.
There
are three major types of memory storage filing systems; short-term memory also
called working memory or immediate memory, intermediate memory and long term
memory also called permanent memory. (Essentials of Medicine)
Short-term
memory (STM) works much like an echo on the canyon wall, it parrots back what
we saw or heard. The duration of STM of what we heard lasts between 7 to 10
seconds and what we saw lasts about ½ second in most circumstances.
We use STM when we retrieve and activate long term memories. The
capacity of STM is very small and holds between 4 to 7 items. Once this space
is filled, any new item randomly displaces one that is already there. This is
why it is much easier to recall a short list such as the digits 6813 where as
9196813949 is more difficult. (Barry Gordon, 1995)
Intermediate
memory covers the time span beginning within a few seconds past and extending
backward for 24 to 48 hours. It is much easier to recall what we had for
dinner yesterday and the day before, but the memory of what we ate for dinner
3 weeks ago is gone.
Long-term
memory covers the memories that extend beyond short-term memory and
intermediate memory. These are memories already in our brains that need to be
reactivated. However, over time long term memories begin to fade.
Successful
memory retrieval relies on a combination of all three-memory storage systems
at any given time.
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Memory
Loss- What is Normal?
Memory depends on the survival and healthy functioning of the neurons. Loss of
memory function is related to an interruption of normal neuron function. The
interruption can take place at many different stages such as communication
between neurons, nourishment and metabolism within the neuron and the repair
of injured neurons.
At
what age do we start losing our ability to remember? Studies suggest that
memory peaks between the ages of 20 to 30 followed by a subtle decline. After
the age of 60 the memory capacity declines and memory loss becomes more
pronounced at the ages of 70 and 80 when a definite decline is noticeable. The
pattern of memory loss can be
divided into 5 groups.
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No
loss of memory capacity or
retrieval
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Normal
Aging- no loss of memory
capacity but have a delayed
retrieval
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Age
associated memory loss
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Mild
cognitive impairment
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Dementia
Not
everyone loses memory function at the same rate and there are some that never
seem to suffer any decline. I am humbled by the ability of R.J. age 83 who
could recall details such as the exact date I purchased my new vehicle several
years after the event. R. J. belongs to a very small hearty group that never
seems to age mentally.
In
people with normal aging, the most common complaint is the slowing down of
mental function with a slight decline in memory. People commonly find it takes
a little longer to retrieve information, however, the information is still
intact.
Some
people have more pronounced difficulty with their memory as they age and have
“Age Associated Memory Loss”. Dr. Ronald Petersen Ph.D., MD, Director of
the Mayo Clinic Alzheimer’s Disease Center, characterizes this group as
having small lapses of memory such as misplacing an item at work or home,
briefly forgetting someone’s name or forgetting to pick up a much needed
item at the store. (NIA; 1999) These memory difficulties develop over a long
period of time and gradually worsen. (Barry Gordon; 1995)
A
new category of memory loss has been labeled Mild Cognitive Impairment (MCI).
Dr. Doraiswamy MD, Director of Clinical Trials in Psychiatry at Duke
University Medical Center, characterizes MCI as having a more consistent and
persistent memory problems than an Age Associated Memory Loss. They have a
significant decline in short-term memory compared to their peers, difficulty
learning new material and family or friends have noticed this decline.
Functioning in activities of daily living have not suffered as a result of
declining memory and with overall cognition in the normal range. Much research
is being done in this area with hopes that severe memory loss may be
forestalled. It is estimated that 12 to 15% of patients with the diagnosis MCI
may convert to AD per year and about 40% after 3 years. (NIA; 1999) This is a
much higher rate of AD conversion than 1% per year over the age of 65 seen in
the general public. It is
believed that MCI is a risk factor for developing AD. However, not everyone
who is diagnosed as MCI will develop AD.
More
serious symptoms and functional impairment characterize abnormal memory loss
associated with dementia. Since
only 50 % of dementia cases are AD, what are the other dementias? Dementias
are classified by cause and belong to the following types: Degenerative (AD,
Parkinson’s Disease, Pick’s Disease), Vascular (Infarcts, Hemorrhage,
Cardiac Disorders); Mixed-Vascular and Alzheimer’s (Bacterial meningitis,
Creutzfeldt-Jakob disease, Multiple Sclerosis); Traumatic (subdural hematoma
or traumatic brain injury); Toxic (Heavy metals, alcohol, some medications),
Metabolic (Vitamin B12 or folate deficiency, Cushing’s disease); Psychiatric
(depression) and Hydrocephalus. The deterioration associated with dementia is
not necessarily diffuse but does affect more than one domain of intellectual
function. Dementia is an acquired disorder, in which at least two domains of
function are impaired, one of which is memory. The other domain(s) can be
language, perception, visuospatial function, calculation, judgment,
abstraction or problem-solving skills. Because of impairment in two or more of
these domains, the demented person suffers deterioration in social and
occupational skills or activities of daily living. These impairments must
result from impairment in mental function and not be due to physical
disabilities. (Kevin Fleming et al; 1995)
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Memory
Loss- What is significant and what are some warning
signs?
We all forget. The results of a “Forgetting Frequency Questionnaire” may
be reassuring. This survey indicated that once a week, the average person
forgot where they put things, had to recheck whether or not they had done
something that they had meant to do such as lock the door and had word finding
difficulties i.e.“ a word on the tip of the tongue”. About once a month, they completely forgot to do something
important such as passing on a message or lost their train of thought while
talking and needed to ask, “Where was I?” (Barry Gordon; 1995)
But
if we forget important things to the point that it interferes with our work or
endangers others, the forgetfulness is more than an annoyance or
inconvenience. When the forgetfulness is consistent and persistent and others
are concerned about our memory, it may be a sign of something more serious.
The Alzheimer’s Association has developed a list of 10 warning signs that
are briefly listed below. (alz.org) Individuals who exhibit several of these
symptoms should see a physician for a complete evaluation.
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Memory
loss that affects job skills.
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Difficulty
performing familiar tasks.
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Problems
with language. Difficulties with word finding ability and fluency of
speech.
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Disorientation
to time and place.
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Poor
or decreased judgment.
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Problems
with abstract thinking.
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Consistently
misplacing things. Placing a wristwatch in the fridge and not remembering
how it got there.
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Changes
in mood or behavior.
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Changes
in personality.
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Apathy
or loss of initiative.
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What
can I do to preserve my memory?
At this point, not one pharmaceutical or herb has been proven to preserve or
improve memory. For a product to get the indication that it preserves memory,
it must have reproducible results in double blind placebo controlled studies.
These studies are vigorous, expensive and require hundreds of participants.
Any evaluation of a study must always consider placebo effect. It is
incredible but true, just wishing to
improve your memory will improve
your memory by 20 to 30%. (Barry Gordon, 1995) It is also important to realize
that not every product we ingest reaches the brain. The brain is isolated and
protected by the “blood brain barrier” which works relentlessly at
filtering the passage of material into the brain.
The
recommended steps for preserving your memory are commonsense; good living,
getting regular check -ups and actively using your memory.
Good
living includes proper diet and water intake, exercise, adequate sleep and
having a positive outlook on life. Building up your cardiovascular endurance
through exercise can improve some mental abilities by 20 to 30%. (Barry
Gordon, 1995) Recreational drugs and excessive alcohol can impair brain cells
permanently. Lack of sleep, high anxiety and depression affects focus and
concentration and therefore impair the registration process of memory.
A
regular check up includes having a comprehensive annual physical and
neurological examination by your physician and should include hearing and
vision tests. If you have memory complaints, your physician should rule out
common physical causes such as hypothyroidism, Vitamin B12 deficiency and
Folate deficiency. Your physician should review your medication profile since
some drugs have been known to impair memory. A brain scan may also be
indicated. If you have a diagnosis such as diabetes or hypertension, it is
imperative that you following your MD recommendations. Uncontrolled diabetes
or hypertension can have a permanent, detrimental effect on your brain.
Actively
using memory is important and can be compared to actively using muscles.
A muscle that is not exercised will wither or atrophy. “ Use it or
lose it” memory exercises are highly recommended. Several techniques are
found in memory improvement books and can improve memory as much as 30 to 40
%. (Barry Gordon, 1995) Rather than passively watching television, actively
engage your memory by reading a book, playing a board game, filling out
crossword puzzles or learning a new skill. Use of memory aides (notes, diary
or recorder) and improved organization (keeping the keys in one consistent
location) can greatly enhance our memory success while reducing the memory
workload.
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What
are scientists doing about memory loss?
It is estimated that 50 compounds are being tested for AD. (NIA, 1999). There
is reason to feel optimistic because great advances have been made in
understanding the neuron on a cellular and a functional level. Several
different types of pharmaceuticals are being tested for memory loss such as
anti-inflammatory agents, estrogen, antioxidants, Nerve Growth Factor
(AIT-082), cholinesterase inhibitors and vaccine. These pharmaceuticals target
either slowing, delaying or preventing memory loss.
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References
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Virginia
Lee (2000) “Alzheimer’s Disease and Related Tauopathies: A Brief
Overview for the Non-Specialist.”
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National
Institute on Aging (NIA)(1999) Progress Report on Alzheimer’s Disease
Pages 2-3, 34
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Barry
Gordon (1995) Remembering and Forgetting in Everyday Life Pages 254 to
256, 108 to 113, pages 44 to 69, pages 269 to 275
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Connections
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Kevin
Fleming, Andrea Adams, Ronald Petersen “Dementia: Diagnosis and
Evaluation” Mayo Clin Proc, November 1995, Vol 70
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Essentials
of Medicine page 747 to 751
Marilyn
Aiello, Duke University Medical Center, Department of Psychiatry and
Behavioral Sciences
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