TH
5018 NE 15 AVE · PORTLAND, OR 97211 · FAX: (503) 229-8064 · (800) 837-8428 · [email protected] · WWW.VESTIBULAR.ORG
Cognitive Aspects of Vestibular Disorders
This document is a transcript of an informal talk given to a support group in the 1980s by
Kenneth Erickson, MD, PhD. For the sake of brevity, some parts of the lecture were omitted.
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 have now
begun to recognize and study a number
of cognitive disturbances associated with
vestibular disorders.
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
with 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.
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.
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 1 of 11
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."
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
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 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
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.
Recent memory
This 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.
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 2 of 11
Long-term 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 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 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.
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 3 of 11
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 involve the front part of that
loop. They are very much a front
executive function of the brain.
The whole frontal lobe of our brain is
involved in all our planning, decision
making, handling two things at the same
time, problem solving, sticking to a task,
mental stamina — a lot of those things
sound very similar to the areas I was
pinpointing for vestibular disorders.
We don't understand how the vestibular
apparatus links in so intimately with the
frontal lobe in terms of the mental
processes we see impaired. That is an
unknown. It will be a very difficult area to
study based on our present knowledge. It
is potentially a fruitful area to study over
future years, however. In any event, the
key problems in vestibular recall are the
input and the output. I say this because
the storage part, the retention part, is
actually not so badly affected.
We know this because we are able to
measure the storage component. You
might call it the tape recorder. Memory
retention involves the temporal lobe and
can be measured by using so-called
recognition tasks. In recognition tasks,
the patient is simply asked, "have you
seen this word in the last half hour or
not?" Patients are given virtually
everything but the answer. It's like a
multiple-choice question.
With that level of assistance, people with
vestibular disorders do exceedingly well.
It is also frustrating as well because on
standard psychologic tests, a vestibular
patient can look darn good. This adds to
their feeling of invalidation. Doing well on
those recognition tasks can make the
patient and sometimes the examiner
believe that the physical and chemical
malfunction is all psychosomatic or
hysterical.
But if the examiner takes it a step further
and asks how good is a person at putting
in the information and then without much
help pulling it out (much more like real
life), that's when we see significant
problems.
Special terms
I've coined a few terms to discuss the
problems that arise when specific kinds of
tests are given to vestibular patients.
First of all, we find that vestibular
patients have a reduced channel
capacity.
We all have a certain capacity to take in
new information at a certain rate; we get
used to being able to do and to do it at
our own rate. We know when we are tired
we'll be a little poorer at it, or when
several things are coming at us at once it
will be reduced; but we know what it
feels like, and we're pretty comfortable
with our rate. It's similar to a computer's
capacity to process information at a
certain speed.
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 4 of 11
This capacity is considerably reduced in
the majority of patients we see in the clinic
with vestibular disorders.
Another area bears on the sequencing
of information. The ability to recall in
what order we learned or heard or were
exposed to information is crucial to later
recalling it in a meaningful or useful way.
For reasons we don't fully understand,
most vestibular patients find it very
difficult to properly sequence information.
If they're presented with a task, like the
one we use in our clinic to measure
sequencing, the "divided attention recall
test," where we break up the person's
attention, we find our patients have real
difficulty. This task is much more like real
life than mere recognition tasks. We
present a series of words to the person
and, not only do they have to pull back
the word that they saw a couple of words
ago (so they're starting to have to reach
back), but at the same time they're
having to sort every new word into a
category. So there are two different
things going on at once, and they're also
having to reach back and recall recent
material.
How many of you with vestibular problems
find it hard to track a conversation,
especially if there's more than one person
conversing? I would imagine that the
majority of you have had that experience.
Even extremely bright people who have
vestibular problems have massive
problems with this. It's also extremely
fatiguing.
Thus the sequencing problem that shows
up in tasks like this is unique. They can
reach back, the people who have taken this
test, and hold back some of that
information, but they often reach back too
far or too recently; it's as though the time
tag, the ability to know just about when
that word happened, is very loose or gone.
We don't understand it, but it's
exceedingly similar to a kind of problem
seen in early Alzheimer's disease. It
seems to indicate a loss of a kind of time
setting or time tag.
Finally, the lack of internal conceptual
validation, the "aha, I've got it"
experience, the sense of being valid
about what you're thinking, seeing the
big picture, being sure you've accurately
completed a detailed task, being certain
you remembered the correct name or
fact, having that satisfying feeling of
"yep, that's the match," — is frequently
gone.
Even though the majority of people we
test are darn smart in many ways, they
lack this sense of rightness. The
vestibular patients we see often do rather
well on the standard kinds of
psychological tests, but we find they have
a real problem knowing they are right,
inside. They may be right 90% of the
time, but they don't have that internal
satisfying feeling.
That's a difficult one to understand, but
we know from studies done years ago of
people with brain injury that deep areas
in the front part of the brain from the
deep thalamus out to the front part of the
brain are very important for locking into a
kind of "gold standard," matching your
sense with what is somehow stored in the
brain and knowing that you are right.
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 5 of 11
Again, it raises fascinating questions
about is there some way when you're
very young that the vestibular system is
wired into this whole area. We have
absolutely no way of knowing that at this
time.
We do know the vestibular system links
with your visual system, and visual
control is very much a frontal lobe
function, but there is no real knowledge
of other networks going into these
memory centers.
Practical ramifications
What are the practical ramifications of all
these deficits that I've been describing?
The three areas of dysfunction I just
listed — the decreased channel capacity,
the diminished sequencing ability, and
that lack of the “aha” experience inside —
those three areas cause incredible
difficulties with simple daily life functions.
Let's start with personal life, your home,
your shopping, your social interactions,
your family responsibilities. The above
difficulties I've spoken of wreak havoc
with your ability to function in any normal
personal setting, from planning a menu
to organizing your day's to-do list, to
tracking your children's conversation.
There's an astonishing contrast between
the ease which most of our patients
remember encountering in social
situations prior to their illness compared
to the difficulty they feel now when they
try to deal with more than one person at
a time. Situations which seemed
hum-drum when they were well now
appear impossible.
Occupationally, any time-locked task that
has to be done by a certain time
obviously is going to be affected. We
don't even have to go into the detail I've
gone into to say that the fatigue that is
felt causes great problems with those
kinds of tasks. But any task that requires
tracking more than one train of thought
at a time, like that of a receptionist
answering phone calls and plugging them
into the right message boxes and so forth
would be dramatically impaired.
Finally psychiatric complications such as
depression and anxiety are almost too
obvious to mention. After this kind of
alteration of your most basic habits of
thought, it's hard to conceive of not
experiencing anxiety, depression, and
disappointment.
Even if you have a supportive family
structure that understands the cognitive
problems, you end up inside not getting
that sense of satisfying "I'm doing what I
should be doing."
That links with that certainty inside that I
spoke about. Even when you're fatigued
and vestibular and you know you put in a
good day and have done the best you
can, that internal lock that says "I know I
did this, I can retrieve what I did today, I
can look at the big picture, and I had a
good day" is not there for most vestibular
patients.
That alone, even within a loving
supportive family and with no financial
problems, would create anxiety and
depression.
Physical & psychological
relationships
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 6 of 11
Why do these kind of memory and
functioning patterns exist among
vestibular patients?
There are three very obvious factors that
many psychologists will raise. Those of
you who have seen psychologists may
recognize these diagnoses. First, pain is
bound to cause problems with
concentration and depression. Second,
anybody with as much fatigue as the
vestibular patient experiences will have a
lot of trouble. Finally, the depression
ensuing from that and everything else
affects people's attention span and
concentration and memory.
So, those of you who have gone through
psychological tests often end up with a
psychologist telling you that you have a
few problems with attention but you're
above average IQ, and there's nothing
much to worry about; in fact, on their
tests you look pretty darn good. The
things that they do see, the mild
attention and concentration problems, are
probably due to the pain, the fatigue, and
the depression.
Well, the hypotheses that we have are
somewhat different than that. We don't
know that ours are correct, but they do
not include the above. The reason that
we don't explain the difficulty vestibular
patients have as due to pain, fatigue and
depression is that if you test people with
pain, with fatigue and depression, they
either don't have this pattern of difficulty
or it's far milder.
If we test people with a lot of pain or
depression or fatigue, they will do badly
on a variety of attention and
concentration tests. On those tests,
however, vestibular patients may do
pretty well. If, instead, we test using the
tasks where we divide up the patient's
attention between sorting words by
category and pulling back recent words,
we find that even when they're feeling
stable and are not in much pain, on this
one test vestibular patients perform
badly.
Obviously common sense leads us to
explore this further. We can only
conclude that this kind of malfunction
seems highly specific to most vestibular
patients. Shortly we will have enough
control patients to publish these findings.
Our hypothesis is that the reason you
have this problem as a vestibular patient
is that your brain stem is affected. The
brain stem is a stalk connected to the
spinal cord. There are nuclei located in
the brain stem that attach to your
balance system; they are also highly
important for keeping your cortex, your
thinking areas, alert and aroused and
attentive.
Could it be that since you're constantly
fighting the mismatch from your visual
input and your disordered balance system
that a very basic mechanism — a
mechanism that was developed as you
learned to sit and crawl and that
influenced how you later manipulated
objects and then walked and spoke and
thought, a mechanism that's taken for
granted and built into very fundamental
habits — could it be that something that
fundamental is being distorted? That the
vestibular and visual disturbance
interferes with nuclei functioning within
the brain stem and thus interferes with
your sequencing of information and
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 7 of 11
impairs and reduces your channeling
capacity?
up against the fatigue problem, which we
can do little about.
It's an intriguing hypothesis, exceedingly
difficult to test. Nevertheless it makes
some sense. Basic problems with reading,
watching letters transpose, problems with
movement and the orienting to the
environment — these are manipulations
of the environment that were learned at a
very fundamental developmental stage.
One of our goals is to try to teach people
tricks or handy ways of remembering
things that would help anybody walking
around the streets, shorthand ways of
remembering things using pictures and so
forth.
Question: Can some of these problems be
described as dyslexia?
Answer: Yes, these symptoms can be
misunderstood as dyslexia, although
dyslexia has some other components to
it.
Question: Is this damage permanent? Will
the brain cells die from not being used?
Answer: We have no way of finding out
the physical damage. The MRI's
(Magnetic Resonance Imaging scans)
often look perfect. It's likely that your
vestibular system is sending inaccurate
information to other brain areas that
don't know how to handle it and/or
information that gets distorted at very
elementary levels of functioning. Those
basic functioning areas seem to need
accurate information from the
vestibular system to think.
Treatment
Can we fix it? That is a very complex
question but obviously among the most
important questions to ask. Our clinic,
which has been doing some of these
studies, is very dedicated to trying to
improve these memory problems. We're
We've discovered if the picture is highly
dramatic and a movement-filled picture,
patients become highly vestibular, and it
interferes with the memory. So we have
to train people to remove a lot of motion
from their images. These tricks are one
aspect of our work. Using them, we have
seen some improvement, but not without
effort and time and learning to make
these strategies become automatic.
Increasing patients' stamina, allowing
them to take in larger amounts of
information is an area which we're highly
interested in pushing. A couple of our
patients have been able to move into that
phase, and we see that slowly, again not
without a lot of effort, the capacity to
increase the amount is there.
I have a guess that part of the reason for
that improvement is that one is learning
new habits — is training him- or herself
to think again. As a vestibular patient,
you must learn to move around in a
slightly different-sized intellectual room.
As you learn, just as in physical
vestibular therapy, compensating
becomes automatic. You become
comfortable with that little basic mental
operation and this one, and you don't
have to be thinking consciously about
every step. These new automatic habits
allow you to take in more.
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 8 of 11
Our goal is to train these habits so people
can actually improve on their
performance and feel the difference at
home. Again it's confounded by the
fluctuating symptoms of the vestibular
condition, by depression, by stress, by all
kinds of other things that enter into your
memory and finally by the fatigue that is
constantly there because of the mismatch
of your vision and your balance system.
Nevertheless, those who have reached
that stage do feel a sense of gratification,
and that drives us on. Our own sense is
that given enough time, people will
develop these new habits. We hope that
we're developing a mental operation
therapy similar to the physical vestibular
therapy. Because it's so much more
subtle and abstract we suspect it will be
very slow going. We feel that the rewards
are there, and we continue to be
dedicated to exploring them.
The future
After completing the initial study that I
mentioned on the divided attention/recall
test, we plan to do two studies in which
we look at the channel capacity, the limit
on taking on new information before
suddenly the slate is wiped clean and
none of it comes back.
We are asking: what is the sequencing
problem when it comes to memory? How
can we get around it? How can we
understand it? Can we actually find some
interesting little patterns that might help
compensate for its dysfunction?
Finally, later on, we hope to study this
very intriguing difficulty with that sense
of closure, of certainty, inside. I suspect
it's a multi-faceted experience that
requires five or six different things to
come together.
Within all this, of course, we have to
include studies of people with pain, but
no vestibular problems, depression but no
vestibular problems, fatigue and no
vestibular problems, head injury and no
vestibular problems. That allows us to
control for some of those confounding
variables that people now use to explain
the problem.
Questions, answers
Question: Do other people have problems
with getting the first part of a word and
then losing the second part, or getting
the first part of a sentence and losing the
second part?
Answer: These are indeed very
common difficulties among vestibular
patients.
Question: What effects might medicine
have?
Answer: Many of the medications for
vestibular problems are sedatives, even
the antihistamines and pain
medications have a sedating effect.
These will have an effect on memory
and concentration. Vestibular patients
who need medication to control their
symptoms are often caught between a
rock and hard place — the vestibular
symptoms cause them cognitive
difficulties, but if they medicate to
control the symptoms, the medication
causes cognitive problems.
Question: I have a problem with getting
the general idea of articles when I'm
reading. Is this common?
© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 9 of 11
Answer: Definitely. In our clinic, we
work on sequence and memory aids, in
order to break the material down into
simpler steps, say, into key points. If
there are more than five or six, then
you will have trouble. Even simple
articles can seem very complex. You
can break reading materials down into
key points, but it's hard work. You need
to pick things that are worth it to you.
Otherwise you'll get too fatigued and
discouraged.
Question: Why do we misread, even
when we know we are misreading?
Answer: It's called a substitute
syndrome. Vestibular patients
experience the syndrome often; it's
very frustrating. I don't know why it's
so rampant in vestibular patients.
Probably it's linked to underlying injury
to the vestibular system that goes
beyond the vertigo, etc. When we
tested a patient who was no longer
having vertigo and whose scores were
rather impressive in other areas, this
"misreading" syndrome still existed.
Question: Do you have any help for
family members?
Answer: A vestibular dysfunction
affects the whole family because it
affects the patient's total life. Family
members need help and understanding
almost as much as the patient him- or
herself. In the clinic, we include family
members' perspectives because they
can sometimes give clues to behavior
that patients aren't aware of.
© 1996. 2006 Vestibular Disorders
Association
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This document is not intended as a substitute
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© Vestibular Disorders Association ◦ www.vestibular.org ◦ Page 10 of 11
TH
5018 NE 15 AVE · PORTLAND, OR 97211 · FAX: (503) 229-8064 · (800) 837-8428 · [email protected] · WWW.VESTIBULAR.ORG
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