Thinking About Thinking
Stuart Kieran, MD
1019 West Main Street
Hamilton, MT 59840
Thinking about thinking
The next several articles will be about thinking processes or cognition
and its change with age and diseases. The loss of these processes, if
severe enough, is called dementia, of which Alzheimer's is one type.
First what are these cognitive processes? There are many which include
memory, language, creative skills, logic, abstract reasoning visual and
spatial abilities and more. One of the most important is memory. We are
very dependent on our memory to function normally throughout the day.
But what is memory. Memory can be divided into short and long term. Short
term memory is roughly analogous to a tape recorder, such as when given
a phone number and you immediately write it down and can remember it for
a few minutes. After that it is either forgotten or reprocessed in a way
that the brain can make sense of. This may not be what actually has occurred
in reality. This is very obvious when several witnesses are asked to recall
a crime scene and each give different renditions of the same event. We
filter, interpret, and prioritize the several components of the event.
While a crime scene is a very dramatic event, we do this for all our day
to day encounters as well. Sometimes the memory is true but it can also
be altered by our own interpretation and experiences. We try to make sense
of what we see and if it seems a little strange, we have a tendency to
bend the reality to make it more understandable. This interpretation,
not the actual event, is what gets recorded as memory. So memory is more
a story we tell our minds than recording of actual events.
Long term memory is usually more stable than short term which is more
fragile. This can be seen when memory declines and a person will first
forget the names of great grandchildren, then grandchildren, then children
and then their spouse or siblings. It is only at the end stage of diseases
like Alzheimer's that one may forget their own name. Another example
is when we smell something and it brings back memories of our childhood
(credit to Marcel Proust). Two reasons long term memory has more staying
power is that it is spread around different areas of the brain, while
short term is only in one area called the hippocampus. In Alzheimer's
disease, this area, the hippocampus, can be seen as visibly smaller on
MRI scanning. The second reason long term memory is more robust is that
it is encoded at times when our brain cells and connections are younger
and presumably stronger.
A common question is what is "normal" memory loss and what is
"serious" memory loss. While this can be difficult to separate
at times, it is common, and not a sign of dementia, when someone has difficulty
coming up with nouns, especially proper nouns, has no other memory difficulties,
and can do their normal functioning during the day. It is so common that
it is sometimes called "dysnomia of aging" and in and of itself
has no implication for further problems.
Another type of memory is called working memory. This is done by the front
parts of the brain, called appropriately the frontal lobes. This is where
one must remember one thing that you are doing in order to finish the
rest of the job. An example would be making something from a recipe where
several steps are required. This may also be the type of memory that is
necessary in complex physical skills, such as dancing and some sports,
which incidentally may be good exercises for the brain to keep it youthful.
This aspect will be discussed in future articles.
The community health column is brought to you this month by a partnership
between Marcus Daly Memorial Hospital and Bitterroot Neurology. For questions
and or comments, please contact Stuart Kieran, MD at Bitterroot Neurology,
1019 West Main Street Hamilton, MT 59840 or call (406) 375-9310. Working
together to build a healthier community!