Aphasia is the name given to language deficits
following brain damage, most commonly strokes. According to the Heart
& Stroke Foundation of Alberta, approximately 1,100 Albertans
become aphasic each year. These patients often face a frustrating
existence with a reduced quality of life. One difficulty in helping
them is that the symptoms of aphasia can vary widely because language
comprehension and production are complex processes that rely on many
different regions of the brain. Understanding the symptoms of aphasia
has proven to be a difficult task, because of the complex relation
between this multitude of identified language functions and the brain
tissue underlying those functions. The relation between brain tissue
and function is variable between individuals. This makes it problematic
to study aphasia using a lesion-based approach, which first identifies
the site of brain damage, and then infers what the problem is from that
information. Most modern aphasia research instead focuses on a
function-based approach to aphasia, which attempts to map the
functional deficit directly by a careful assessment of the language
system’s function.
Click the play button to
view this animation which comes from the ALFAB. What is being tested
here is the ability to produce a sentence using the verb "put" in
combination with the objects in the movie in a particular order (the
green element must come first in the sentence, the yellow second, and
the red last).
The Alberta
Language Function Assessment
Battery (ALFAB) is a computerized battery of tests relating to many
different aspects of language function. It is computerized in order to
enable us to test many different aspects of language at the same time.
The results are scored by a computer program that can look for patterns
of performance within tests and between tests. There are so many
patterns that need to be considered that it would be very difficult for
a human being to score the tests by hand.
Most of the tests in the ALFAB look at
single word access, which is surprisingly complex. Words can be
produced and understood in different ways, through writing or speech.
Since some aphasic patients have troubles with one form but not the
other, we need to test both written and spoken words. Different kinds
of words are stored in the brain in different places. We need to
consider the difference between abstract nouns like ‘peace’ and
concrete words like ‘dog’, as well as the difference between verbs like
‘eat’ and nouns like ‘cat’. Sometimes aphasic patients can read written
words or repeat spoken words, but not understand what those words mean,
so we need to test access to word meaning independently of access to
word form (how the word looks or sounds). Words that are similar to
many other words- as ‘cat’ is similar to ‘hat’, ‘bat’, ‘kit’, and
‘can’- are sometimes easier and sometimes more difficult to access than
unusual words like ‘aphasia’. For this reason we need to carefully
control for how similar words are to other words, and test different
kinds of similarity. Some words are made up of smaller word-like pieces
(called ‘morphemes’), as ‘running’ is formed from the words ‘run’ and
the ending ‘ing’. Some aphasics have particular trouble with
understanding or producing complex words that have more than one
morpheme in them, so we have tests designed to examine this aspect of
language.
Of course words are also used together,
in compound words such as ‘blackboard’ as well as in much more complex
ways in sentences. Some of the tests in the ALFAB are designed to
assess ability to create and understand written or spoken compound
words and sentences.
There are many other complexities
in studying language. Because we are trying to test as many aspects of
language as we can, we need to have many tests and occasionally many
items in each test. Some of the tests ask you to look at or listen to
words and make various kinds of decisions about them. Others ask to you
to say or write the name of a pictured item or repeat a spoken word or
read a written word. Still other ask you to speak or write sentences to
describe short cartoons.
The ultimate goal of this research is to
build a large database of scores on all of the language tests. By
analyzing this database, we hope to make discoveries about how language
is organized in the brain, and how it can break down following brain
damage.
To download the ALFAB (Mac and Windows versions available) please
click here.
