this online textbook chapter on language. The emphasis will be on
a cognitive neuropsychological approach, with the data from brain-damaged
individuals providing insight into how the unimpaired brain processes
language. To set the scene, we will introduce you to a patient who
has suffered a stroke affecting various aspects of his language
ability. We will show you some of the things which are now difficult
for him, and how surface appearances do not reveal those difficulties.
Listen to his conversation with Dr Randi Martin, first of all. Notice
how he seems to understand the questions put to him, with no trouble.
Notice also how his speech production is slow, with his taking much
more time than most would to express himself, even though the topic
is something he has talked about many times in the past.
One of the things you may wonder about is whether he has some
speech difficulty which prevented him from speaking more fluently
than that. We need to look at some other task where he has to
speak but does not have to construct sentences in order to rule
out that possibility. One such task is repeating words. Here is
another clip, showing ML's single-word repetition.
You can see that he is able to speak promptly, without hesitation,
when he repeats the words. So, it is not the case that his conversation
is so hesitant in conversation due to a pronunciation difficulty.
We hope you noticed how he understood the questions put to him
by Dr Martin. His comprehension of sentences is not as good as
it would have been before his stroke, however. To give you an
idea of this deficit, take a look at the following graph, showing
his performance on a comprehension task compared to that of a
group of eleven controls who were round about his age and education
level. There were five different sentence types and he was appreciably
worse than the controls in accuracy on all five types. The pattern
in his errors is qualitatively similar to the controls, however,
indicating that the difficulty of the structures (from left to
right, difficulty increases) had an impact on him, just as it
did on the few errors the controls made.
Now watch ML performing this language task (note that he uses
his index finger for YES and ring finger for NO in his judgments
of plausibility). When he is wrong, you will hear a buzzer (the
items are from the practice set). When he is right (on a test
item), the time he took to respond will appear on the screen.
Notice how slow the time on the fifth one is, which is hard because
of its complex grammatical structure.
A stroke generally affects a number of different aspects of language.
Just to show you more ways in which ML was affected by his stroke
(on the left side of his brain, toward the front), listen to him
now reading words and non-words aloud. Non-words are made up from
real words by substituting one or two letters to make a pronounceable
non-word which does not occur in the English language. From being
able to read real words fairly well, he now shows a lot of difficulty
coping with these made-up words. You will see the word written
on the screen and so will be able to judge for yourself whether
you could have found a pronunciation for each one.
aloud words and non-words
This difficulty reading non-words while being able to read most
words is curious until you understand the processes by which most
of us read. What has happened with ML is that he can no longer
make use of the rules he learned as a child about how to pronounce
letters and letter sequences. He is, however, able to refer to
his memory for the overall pronunciations of words that he has
seen before. Because he never saw these non-words previously,
he has no stored pronunciation of them and, without the ability
to sound out the letters, struggles to pronounce them, often relying
on a word he does know that is similar in visual appearance.
Another curious deficit ML has is with naming pictures of items
from the category of body parts. Notice how he copes better with
naming pictures of other categories, such as fruits, vehicles,
furniture, kitchen implements, yet struggles to find the names
of some body parts.
This curious island of difficulty is not unique to ML, though
we still do not understand what brings it about. It is an illustration,
however, of how it is necessary to zero in on quite particular
aspects of the skills being tested. It is not good enough to have
just a mix of pictures to name; they need to be selected from
different categories known to the patient, across the categories
the pictures need to be of similar familiarity and degree of use
in the language, and they need to be of similar visual appearance,
with no individual category disadvantaged by being more complex
to illustrate than any other, or more uniform amongst its members
than the others. Because ML could read real words well, and could
name the other categories well, it is obviously not the case that
he has any trouble with perceiving or recognizing pictured objects.
This little exploration of ML's deficits has given you, we hope,
a bit of an idea of how the cognitive neuropsychology approach
to testing is carried out. There will be many opportunities in
this chapter to participate in tasks yourself and to get a score
similar to what is obtained from patients in researching their
difficulties. This research helps in diagnosis and helps us understand
how the intact brain probably functions.
To conclude, listen to one more interview with ML in which he
describes what it is like to have a stroke and some of the things
he has to cope with in his daily life.
on living with a stroke