Cognitive Aspects of Vestibular Disorders!

COGNITIVE ASPECTS OF VESTIBULAR DISORDERS pt. 1

From: “georgia”
Date: 29 Jul 2005 20:20:45 -0700

1989
COGNITIVE ASPECTS OF
VESTIBULAR DISORDERS
VEDA Conference – Portland, Oregon
The following is a transcript of a lecture by Kenneth Erickson, M.D.,
at
a VEDA conference held in Portland, Oregon.

Patients and families, of course, have known for a long time that
vestibular disorders bring about cognitive difficulties. Some
psychologists and neurologists here in Portland for at least five
years,
crystallizing in the last two or three years, have now begun to
recognize and study a number of cognitive disturbances associated with
vestibular disorders.

COGNITIVE DISTURBANCES
What is meant by cognitive disturbances?
Cognitive disturbances involve a difficulty in basic mental operations
such as memory, paying attention or focusing attention on something,
and
in prolonged concentration. They also involve shifting attention from
one subject or idea to another. People with cognitive disturbances
have trouble in perceiving accurate spatial relationships between
objects, in comprehending or expressing language, and performing
calculations, and in a number of other areas.

These are areas that psychologists routinely test when they are doing
so-called neuro-psychological exams.

A brief run-through of the kind of cognitive dysfunctions that we know
of in vestibular disorders would have to include the following areas:

First of all, vestibular patients exhibit a decreased ability to track
two processes at once, something we usually take for granted.

This ability requires a rapid shifting of attention. A good example
is when you are driving and you have one person approaching
unexpectedly
coming out of a left-hand lane and another car coming behind you
unexpectedly on your right side. Suddenly there are two things that you
need to monitor and pay attention to at the same time. This might
have come easily to you at one time, but if you now have vestibular
difficulties, it’s very hard.

Another example is when you have conflicting emotions inside of you,
if,
for example, there are two different things you want to do at the same
time. The sensation you feel is confusion. Because of your
cognitive problems, you may find it very difficult to express that
confusion.

These are only two concrete examples of a pervasive problem.

The second area of cognitive problems vestibular patients exhibit is
difficulty in handling sequences. This includes a wide range of
sequences. It pertains to the mixing up of words and syllables when
you’re speaking, to the transposing or reversing of letters or numbers,
to having trouble tracking the flow of a normal conversation or the
sequence of events in a story or article. All of those have been
very frequent complaints of the vestibular patients that we see.

A third area would be decreased mental stamina. That speaks for
itself. For a vestibular patient an hour or two of concentration is a
special blessing, and most days 15 minutes of intellectual
concentration
is very fatiguing.

The fourth area involves decreased memory retrieval ability, the
ability
to pull out information from your long-term memory store reliably.
You might hit it most of the time, but you do not have a reliable rate.

Number five is a decreased sense of internal certainty. This is a
peculiar way to state it, but it is exceedingly accurate.

Vestibular patients with on-going physical problems have a frustrating
lack of closure. They lack that “ah-ha; I’ve got it now; I see the
big picture.” Or “that’s what I was trying to remember; I know it’s
that.” They lack that kind of certainty which measures an idea or a
conversation or a social situation up against some internal “gold
standard.” Vestibular patients often lack internal certainty.

Finally, people with vestibular disorders experience a decreased
ability
to grasp the large whole concept. The ability to see the big picture
or the forest for the trees is very elusive for someone with vestibular
disorders.

MEMORY PROBLEMS
I’d like to discuss these areas but most specifically memory problems
in
vestibular disorders; for most people that I see the memory problem is
the most pervasive and troubling one.

To begin with I’d like to address what is known about stages of
memory.
Using human and animal studies, scientists have found out that there
are
varying distinct stages of memory, and these are tied in with distinct
physical areas of the brain.

(We’ll ignore sensory memory.)

Immediate memory is where I’d like to begin. This is the ability to
hold
a name or phone number in mind for up to 30 seconds and sort of juggle
it around while you’re walking over to the telephone. This kind of
memory takes concentration, and if any of us, sick or well, are
suddenly
distracted by a small child or something, it may be gone. It is a
very fragile store of memory, about 30 seconds long. If the phone
number stays longer after distraction, that’s because it’s gotten into
recent memory.

The recent memory area has to do with taking new information and
recruiting it into long-term memory. This is a key area that many
vestibular patients complain of.

Recent memory can be sub-grouped into declarative memory, which refers
to information — the sort of thing you’d pick up in a textbook or an
article or a conversation — and procedural memory, which refers to
procedures — how to do something. A number of vestibular patients
have noted that procedures tend to come easier than pulling out facts.

Thus if there’s a logical sequence that they are familiar with from
before their injury, and they can fit the new information into that
sequence, they have less difficulty than with placing new
non-sequential
information into their memories.

These kinds of memory are located in different areas of the brain, just
as are the immediate memory and the sensory memory.

Finally if you’re successful, the long-term memory store is filled with
the information you want and can remember. It goes into what is
called remote memory, and that store of information and sequences is
diffused throughout the brain.

The areas of the brain which are keys to memory are the temporal and
frontal.
If we look at microscopic sections of the brain, we see our brain cells
are tied together with an enormous amount of interconnections. This
is particularly true in areas that are called “association
areas.”

That’s a handy name because to remember things you have to form
associations and pull them out by associations, and throughout the
front
part of the brain, throughout areas that are called tertiary in other
parts of the brain, you have an enormous mass of interconnections
between the brain cells.
Some brain cells have 100,000 connections to other brain cells. It’s
no wonder that we can store an enormous amount of information; some
scientists think it may be limitless.

When we take a look in the deep areas of the brain, as though it were
sliced in half, there are some structures that are very relevant to
what
I was just speaking about.

Immediate memory involves a part of the cortex that is traveling
between
where you hear and process your hearing and the front part of the brain
where you speak. It’s a kind of traveling loop from the hearing
processing center, the auditory area, around through some fibers to the
speaking area, (Broca’s area). It is this area where strokes can
impair the immediate memory ability enormously and very specifically.
In some stroke victims, just that kind of memory gets affected.

Going on, recent memory, the one that allows us to store information
for
a long period of time, is housed in a couple of areas. It requires
the ability to input the information, which is very much a frontal-lobe
function connecting into deep structures.

Then there’s a complex loop, that’s been studied now for 45 to 50 years
that allows memories to cement down over minutes to months. The
hippocampus, the long banana-shaped organ on both sides is the key area
that allows us to fix the information over weeks and months.

If there are strokes or other damage in this area, a person becomes
virtually locked in time. They do not pick up any new information.
They might sound very intelligent based on their old information, from
before the stroke — that’s still there for them. They might sound
very intelligent in terms of something you are just saying to them this
instant, but if you ask them what we were talking about five minutes
ago, or half an hour ago, that information is gone.

Now we speculate that this area, this entire area, is somehow affected
in people with vestibular disorders because recent memory ability, the
laying down of new information is very confounded and difficult, in
comparison to their pre-accident or pre-surgery history.

Let’s talk a few minutes about stages of information input and
retrieval.

The input stage is called acquisition; you’re acquiring information.
The storage stage is called retention, the ability to retain over
minutes or months or years. And the retrieval, the output stage, is
called retrieval. The acquisition and retrieval stages I mentioned in
this diagram involve the front part of that loop. They are very much
a front executive function of the brain.

.

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