Table of Contents
2. A Survey of the Brain Structure and the Language Areas
3.1. A Definition of the Term Aphasia and the Causes of Aphasia
3.2. The Main Types of Aphasia
3.3. The Recovery from Aphasia
4. Aphasia in Bilingual and Multilingual Persons
4.1. Aspects of the Research on Aphasia in Bilinguals and Multilinguals
4.2. Different Theories of Additional Language Areas
4.3. The Recovery of Bilingual and Multilingual Aphasic Patients
Brain diseases and disorders are fields of neurology that have still not been fully examined. Neurologists are constantly facing new mysteries concerning the processes that take place on in the brain. Especially the aspect of language offers a wide spectrum for research, from the medical point of view as well as from the linguistic one. As I will concentrate on the aspect of language, or more precisely the affection of the faculty of language, which means its production and comprehension, the affection aphasia offers a good example. Aphasia is a very complex problem, and it is still not totally examined by scientific researchers and brain specialists. The field of aphasia includes many different kinds of aphasia, different clinical pictures, symptoms, and recovery patterns. At any rate, the patients have difficulties in producing or understanding language, although to different degrees.
Aphasia in bilingual and multilingual persons is a field of neurology that deserves further research. It offers new aspects to the research on brain activity, and it offers the opportunity of approaching the problem of aphasia in a new way. Nevertheless, there are different, one word even contradicting theories from specialists all over the world concerning the impact of aphasia on speakers of more than one language and the reasons for it, some of which will be presented in this research paper.
As this research paper is written in order to take a closer look at the problems with language in aphasia, it is inevitable to present some medical facts and theories in order to explain the impact of aphasia on the production, understanding and recovery of language. I will start with an introduction to the physical structure of the brain, especially on the areas that are associated with language. Further on, a definition of aphasia, its causes, and a description of the different types of aphasia and their specific symptoms will be given. As the process of recovery is extremely interesting and the observation of it important because it allows us to draw conclusions on how the brain works, a section of the research paper will be devoted to this point. Moreover, the case studies of bilingual and multilingual aphasic patients offer interesting aspects for linguistic and medical research because of the possibility of understanding how language is stored in the brain, and whether different languages are stored in different parts of the brain, perhaps even in the other hemisphere. Furthermore, the way in which bilingual and multilingual aphasic patients recover their language is interesting as well.
Ultimately, I hope that this research paper on aphasia will help to give an insight into scientific research, and the way aphasia affects the language abilities of monolingual people as well as bilingual and multilingual people.
2. A Survey of the Brain Structure and the Language Areas
The largest part of the human brain is the cerebrum, which is divided into the left and the right cerebral hemispheres. The two hemispheres are connected by the brain stem, which can be further subdivided into the mid-brain, the pons and the medulla oblongata. It is an interesting fact that each hemisphere controls the opposite side of the body. Furthermore, it is often said that the left hemisphere is dominant for analytical tasks, while the right hemisphere is associated with creative abilities and emotional expression. But this way of defining the functioning of the hemispheres would oversimplify the processes that are going on in the brain. Scientific research has shown that the dominance for one ability often cannot be clearly assigned to only one of the hemispheres. Even the idea of the asymmetrical functioning of the hemispheres does not apply to all patterns, as the example of language shows. Generally, it is considered as an established theory that the left hemisphere is dominant for language in right-handed people. But this does not automatically allow the conclusion that the right hemisphere is dominant for language in left-handed people, because “[l]eft-handers are by no means a homogeneous group, and in over 60% of cases the left hemisphere is either dominant for language or very much involved (mixed dominance)” (Crystal 258-59).
The surface of the cerebrum, the so-called cerebral cortex, is made of grey matter, which consists of nerve cells. Beneath the cortex is a body of white matter, consisting of fibre tracts, which transmits signals between the different parts of each hemisphere and between the cortex and the brain stem. The surface of the cortex is folded in on itself, and thereby produces many convulsions. These convulsions are separated by fissures. The median longitude fissure separates the two hemispheres, but it does not extend through the whole cerebrum; lower down, the hemispheres are joined by the corpus callosum. Through this connection, information can be transmitted from one hemisphere to the other. Other important fissures are the central sulcus, also referred to as the fissure of Rolando, and the lateral sulcus or Sylvian fissure. These fissures are used in order to divide the brain into its four main lobes: frontal, temporal, parietal, and occipital. Although there are different brain areas that make contributions to language skills, it is a commonly accepted point of view that the areas which are concerned with the processing of speaking, listening, reading, writing and signing are mainly located around the Sylvian and the Rolandic fissure, as for example Broca’s area, which is the “[a]nterior area of the cerebral cortex concerned with the planning and organisation of speech” (Byers Brown and Edwards 216), and Wernicke’s area, the “[r]egion in the superior part of the temporal lobe of the cerebral cortex. Its function relates to the understanding of spoken language” (Byers Brown and Edwards 218).
Further on, the cerebellum has to be mentioned, as it is the “[p]art of the brain which regulates and modifies movement through input from sensory pathways and through its connection with subcortical and cortical areas” (Byers Brown and Edwards 216). Therefore, it is also important for the transmission of verbal signals from the ear and the use of this information for the production of speech.
Despite the fact that it is clear how the brain is structured, it still has not been fully examined how the different regions work; in how far interactions between the different areas take place; and whether other regions can take over the task of an area that is somehow affected or damaged. Several theories of how the different areas are involved in the mental processes and the control of body functions and movements exist, but neurologists are still debating the different approaches. The theory of localization and the theory of equipotentiality are very much at the centre of this discussion. The theory of localization assumes that a certain area of the brain is related to a certain ability: “[s]upport for this theory came from the work of such neurologists as Paul Pierre Broca (1824-80) and Carl Wernicke (1848-1905), who had found that damage to specific areas of the brain correlated with the loss of certain kinds of linguistic ability in their patients” (Crystal 260). But this theory has been debated from the beginning on, and further studies have shown that the theory of localization is not able to explain all the effects on the faculty of language if brain areas have been injured or destroyed. The observation of many cases even clearly contradicts this theory.
There are now cases on record of patients whose Broca’s and Wernicke’s areas were unaffected by lesions, but whose linguistic ability was nonetheless seriously impaired; and conversely, there are cases of patients who have even had Broca’s area surgically removed in both hemispheres, and who were still able to speak. (Crystal 260)