Testing Theories: Using Aphasia Intervention Research to Gain Theoretical Insights – Nadine Martin
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Testing Theories: Using Aphasia Intervention Research to Gain Theoretical Insights – Nadine Martin

People think treatment research is just about
finding a good method. It’s actually got more value — it can be used to test theories.
And that’s very important. The hardest part, I think is finding the interesting research
question to begin with. It has to be of interest to you. I came up with mine — I must say,
I came up with it because I worked as a clinician for a number of years. It began with an observation. That individuals
who have language impairments in aphasia also always have restricted verbal short-term memory
spans. That spurred my investigation of why are these two related? How could these be
related? At the time I was doing this there were two
theories about how language and short-term memory were related. One was that words that
we process are just sort of processed and then held in some separate verbal short-term
memory store. That’s one approach. Then the other approach was that retaining
information for short periods of time happened at all levels of word processing. So you hold
onto its meaning for a short time, its sounds. Your brain has to hold onto these things while
you’re preparing to say a word, or if you’re repeating a word — so the verbal short-term
memory is really intrinsic to word processing. I was intrigued by this idea, and I said,
I think that may be why they are both impaired in aphasia. My theoretically-oriented testing began with
trying to find evidence for that. There were two sources of evidence for that that I can
talk about. One is developing associations between two cognitive abilities. So, one ability
is word-processing. You need a good measurement of word-processing. Another is a good measurement
of short-term memory span. Over a number of years, I collected data from
about 50 or 60 people with aphasia, and I collected it on measures of word processing,
picture naming, and word recognition — so, is this a word or not a word. Then each one
also got measures of verbal span. Then what you do is you run regression analyses correlating
— associating or correlating one measure with the other. The goal is to find out if
there is a severity continuum so that you want to find an association between a person’s
level of impairment of the word-processing and how short their verbal short-term memory
span is. You would expect smaller spans with more severe impairments. This is called a
severity continuum. We did find that association. So that’s one
approach to finding that. And then the second approach is, we had the
good fortune of evaluating an individual longitudinally. We began to test him very early on. He had
a stroke after surgery for an aneurysm. We followed him for a year or two, and after
about a year and a half his word processing got better, and there’s other elements that
I’m not going to go into detail about that, but his pattern of error in repeating words
changed for the better, and his span got bigger. That’s just an example of how there’s another
type of association. As he gets better, both of these abilities get better in parallel. So, that’s fine. And we have other studies
that we did that showed certain associations between these two. But associations are not
enough to establish a causal relationship — that verbal short-term memory is causing
the word-processing, or vice versa. It just simply says they’re associated. That really was part of our theory, that the
language problem is actually holding onto or maintaining the verbal representations.
So the short-term memory is what’s intrinsic to the word-processing itself. So, another approach to testing this, and
maybe establishing a more causal approach, is to actually try to treat the disorder.
If we had a third construct that we said caused both these impairments — and that was the
ability to hold onto or retain the activation of the semantic and phonological representations
of words. So, to test that you have to actually treat the problem. You have to come up with
— you have to find a way, if you say that that’s the problem, you have to treat that
problem, then both should get better. Just the way the young man’s abilities got better
as he recovered, so we hypothesized that was the ability that was getting better. So that’s where we’re at right now. We have
a couple of case studies where we’ve actually developed a treatment protocol to — we kind
of turned the problem on its head. If someone can’t hold onto information for a very long
time, that’s what we’re going to treat. We’re going to ask them to process words, but with
increased memory load. It’s a very simple means of increasing memory load, we ask them
to hear a word and then wait five or ten seconds and then repeat it. And they’re very bad at
that, their performance goes down. But then with training, they get better. So, you can begin to demonstrate a causal
relationship if what you say is the problem, and you’re treating that directly, and the
symptoms get better, then you have better grounds for saying one causes the other. And, one more thing I wanted to say, just
about methodology. You can do this in a whole treatment study. But it’s probably better,
first, to do what we call a facilitation study, which is a short-term, you want to test your
method first — which is what we’re doing now, to make sure that in a one session treatment
protocol, you see if there’s an immediate effect, even if it doesn’t last for very long. That’s to me, is a very good way, at least
in my area of study with adult aphasia patients, people, to connect theory with the treatment
and in the middle of that is the evidence you’ve established. In general, I feel that
our field does call for evidence-based practice, which is very good, but I’m also very much
an advocate for having a theoretical base for that, as the field is, but I think it
could be emphasized a little bit more.

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