Aphasia: A Language Disorder

Biology 202
1999 First Web Reports
On Serendip

Aphasia: A Language Disorder

Joseph Xiong

"My most valuable tool is words, the words I can now use only with difficulty. My voice is debilitated - mute, a prisoner of a communication system damaged by a stroke that has robbed me of language," stated A. H. Raskins, one of approximately one million people in the United States who suffer from aphasia (1), a disorder which limits the comprehension and expression of language. It is an acquired impairment due to brain injury in the left cerebral hemisphere. The most common cause of aphasia is a stroke, but other causes are brain tumors, head injury, or other neuralgic illnesses. Of the estimated 400,000 strokes which occur a year, approximately 80,000 of those patients develop some form of aphasia (2). Another important observation is that within the United States, there are twice as many people with aphasia as there are individuals with Parkinson's disease (2). Yet, what is so astounding is the lack of public awareness about aphasia. Aphasia attacks an intricate part of a person's daily life - the simple act of communication and sharing. The disbursement of such a tool deprives an individual of education learned through their life, often leaving the ill fated feeling hopeless and alone. In considering the effects of aphasia, a deeper analysis of the two most common forms of aphasia will be examined: Broca's aphasia and Wernicke's aphasia. While both forms occur usually as a result of a stroke in the left hemisphere of the brain, their particular site of impairment produces different side effects in an individual's comprehension and speech. These regions have been further studied through experimental researches such as positron emission tomography (PET). Moreover, although there is currently no cure for the disorder, there are treatments and certain guidelines to follow when encountering an aphasic.

In physiological terms, Broca's aphasia and Wernicke's aphasia occur in the left hemisphere of the brain, which is responsible for controlling the right side of the body along with speech and language abilities. Broca's aphasia affects the frontal lobe adjacent to the primary motor cortex, and Wernicke's aphasia affects the posterior portion of the first frontal lobe (3). A general distinction made between the two disorders are that Broca's aphasia limits speech, while Wernicke's aphasia limits comprehension.

Broca's aphasia characterizes patients as people who has loss the production of complete sentence structures in speech and writing. Although the individual may retain the usage of nouns and verbs, the aphasic may have lost all forms of pronouns, articles, and conjunctions (3). Broca's aphasics struggle to speak more than one word at a time but shows signs of enormous effort; thus, patients with Broca's aphasia is characterized as "non-fluent aphasia" (4). Here is an example of a Broca's aphasic speech: Yes ... ah ... Monday ... er Dad and Peter H ... (his own name), and Dad ... er hospital ... and ah ... Wednesday ... Wednesday nine o'clock ... and oh ... Thursday ... ten o'clock, ah doctors ... two ... an' doctors ... and er ... teeth ... yah. (3) This passage shows the difficulty in interpreting a patient with Broca's aphasia. This particular aphasic may be trying to explain that he has a dental appointment at the hospital, or that his dad had an appointment. However, amazingly the Broca's aphasic comprehension level is less impaired. Case studies have shown that Broca's aphasics retained a good amount of their comprehension level. In an experiment to prove this, A. Caramaza and E.B. Zurif tested a Broca's aphasic comprehension level through sentence structures, whose nouns are irreversible as in the sentence: the girl is reading the yellow book. In this portion the aphasics tested rather well, because they managed to understand the sentence. However if the noun is reversible, such as the dog chased the cat, then their ability to recognize the sentence drops (3). This shows that Broca's aphasics retain a good majority of their comprehension level.

Wernicke's aphasics have different types of symptoms. Individuals with Wernicke's aphasia speak extremely fluently but with no informative purpose (3). In this respect, Wernicke's aphasia is known as "fluent aphasia" (4). An example of a Wernicke's aphasic speaking is as follows: Well this is .... mother is away here working her work out o'here to get her better, but when she's looking, the two boys looking in other part. One their small tile into her time here. She's working another time because she's getting, too. (3) Clearly, the aphasic has problems expressing his thoughts to their audience. The sentence structure does not follow correct grammatical patterns, and ultimately, there is no meaning. Moreover, their comprehension level is more reduced than a patient with Broca's aphasia (3). In the same case studies by Caramaza and Zurif with Broca's aphasics, in which irreversible and reversible nouns were placed in sentences, Wernicke's aphasics tested poorly on both occasions (3). Thus, Wernicke's aphasics have lost a majority of their comprehension ability.

N. Geschwind proposed a pattern for language function from examining the expressive behaviors of aphasics. He proposed that If a visual input is noticed, a message is sent to the visual center, the occipital lobe. This message then travels to Wernicke's area where the information is processed and linguistic words are formulated. The next step involves the message being sent to Broca's area, which translates the signal to motor commands that travels to muscles to induce a form of language expression. If another form of sensory is noted, the first signal travels to the sensory association center in the parietal lobe and follows the same pathway (3). Using this model as a guide to conceptualize the two forms of aphasia, the role of region specificity is enforced. If a patient has Broca's aphasia, although small levels of comprehension are impaired, forms of speech are near distinct. If a patient suffers from Wernicke's aphasia, their comprehension level is damaged but production of language is left remotely intact.

Experimental studies also have been done to verify the region specificity. One such approach is positron-emission tomography (PET). In PET, an individual is injected with radioactive glucose into their blood stream and monitored for levels of radioactive glucose consumption throughout the brain region. Glucose consumption occurs in regions where the brain is active. In order to determine region specific properties, high glucose consumption regions are depicted in color code shown in a PET scan. Physicians use PET scans to determine the extremity of the disorder and define brain functions (5).

Although, aphasics may never recover completely from their disorder, there are various techniques available for treating and increasing communication skills for an aphasic. Some specific techniques are (6): 1) imitating or repeating sounds; following commands 2) work on the functions they have retained 3) melotic - increase language skills through using music Another interesting approach is the use of alternative augmentative communication (AAC). The basis behind an augmentative approach is primarily based on symbols. The program known as Minspeak emphasizes the use of symbols that may have various meanings. These symbols are placed in context with one another tocreate an expression. An example is CUP, which could mean "drink", or the verb "to drink" with a action symbol. It could be linked in such an order: CUP + COW = "milk", or CUP + COW = "milk" + action symbol + CUP = "to drink." Another crucial point is that these images have to be transparent, if the patient does not know them, then he/she must be taught them (7).

In considering the two types of aphasics and the forms of treatment, an aphasic may never recover from the disorder. In the case of Broca's aphasia where the effect is mainly speech oriented, the individual does not loose their comprehension level entirely. As for Wernicke's aphasia, the loss may have more relevance because an individual may loose their entire comprehension level. It is crucial to say that aphasia completely changes a person as a normal functioning human being. Although his physical attributes are present, depending on the severity of the disorder his mind may be lost. And even though treatments are available to help the aphasia regain some communication skills, what is lost is lost. It is as if the individual must start from the beginning again only to learn that the extent of what he/she learns is already limited.

WWW Sources

1)Story of an Aphasic

2)Aphasia fact sheet

3) Carroll, David, Psychology of Language, third edition, Brooks/Cole Publishing Company, 1999, p.334-346

4)Aphasia fact sheet

5)Auderisk Terasa, Auderisk Gerald, Biology: Life on Earth, Prentice Hall Inc,NJ, 1999, p. 23 & 676-677

6)Quick Aphasia Fact Sheet

7)Augemtive Treatment

8)American-Speech-Langauge-Hearing- Association

9)National Institute of Health aphasia fact sheet

10)Stroke Fact sheet