LINGUIST List 11.487

Tue Mar 7 2000

Review: Obler & Gjerlow: Language and the brain

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  • nschille, obler

    Message 1: obler

    Date: Mon, 6 Mar 2000 22:51:21 -0500 (EST)
    From: nschille <nschillewjh.harvard.edu>
    Subject: obler


    Obler, Loraine K. and Gjerlow, Kris (1999), "Language and the Brain", Cambridge University Press, Cambridge (UK) (Cambridge approaches to linguistics). ISBN 0-521-46641-5. Paperback. xviii+206 pp.

    Reviewed by Niels Schiller, Harvard University

    This book presents a brief introduction into "the study of language in the brain." The book is divided into twelve chapters, mostly focusing on language use in brain-damaged patients. Each chapter ends with a brief summary. The text part comprises 168 pages, followed by a glossary covering many of the technical terms from the field of neurolinguistics that are used in the volume. The glossary is followed by a very selective list of further readings, a list of references, an author index, and a subject index.

    The book starts with an attempt to define more exactly what the study of neurolinguistics involves. Due to its multidisciplinary nature, this is a difficult job, but it seems to be clear that linguists, psycholinguists, neuropsychologists, as well as neurologists all have an interest in how language is structured in the brain. In the first chapter, the authors give a brief history about the field of neurolinguistics. They mention the classic works by Broca and Wernicke, as well as the Boston School and its role in modern aphasiology.

    The second chapter provides a basic overview of the neuroanatomical structures in the brain. The reader is familiarized with the architecture of neurons and how neurons communicate with each other via electrochemical processes. Furthermore, the division of the cortex into lobes is described, and the most important gyri and sulci are briefly mentioned. The reader is also introduced to the well-known and still widely used division of the cortex by Brodmann (the so-called "Brodmann Areas").

    Armed with this information, the authors present the most important research methodologies for localizing the hemispheric dominance for language in Chapter 3. These include the investigation of brain- damaged patients, the anesthetizing of one hemisphere (the so-called "Wada test"), tachistoscopic presentation to only one visual field, dichotic listening, and the investigation of split-brain patients. Data from all of these methods suggest that the dominance of the left hemisphere for language for most people is uncontroversial. What is more difficult to determine is which areas in the left hemisphere are responsible for what kind of linguistic processing. Historically, research on this question began when Broca and Wernicke presented their patients more than 100 years ago. So-called "Broca's aphasics" are considered to be non-fluent in speech production while comprehension is relatively spared. In contrast, so-called "Wernicke's aphasics" are relatively fluent, but their speech usually contains a lot of circumlocutions and phonemic paraphasias, i.e., sound substitutions, rendering their speech hard to understand; their comprehension is severely impaired. With the help of cortical stimulation and, above all, modern brain imaging techniques such as PET, (f)MRI, and ERP, it is possible to localize lesions in brain-damaged patients and to identify the activity of brain areas in healthy subjects while they are engaged in certain linguistic tasks.

    The next two chapters (Chapters 4 and 5) are about the classification of aphasic syndromes and their underlying symptoms. Aphasia is an impairment in the area of language without other cognitive deficits. Broca's and Wernicke's aphasia are described, but an introductory book like the present volume does not allow for explanations of much detail. What is helpful, however, is that the authors provide examples of what the speech of certain patients sounds like (usually descriptions of the "Cookie Theft" picture). Other forms of aphasia, such as conduction aphasia, anomic aphasias (naming problems), pure word deafness (due to injury to Heschl's gyrus), and subcortical aphasias are briefly mentioned as well. The phenomenon of agrammatism, i.e., speech production without producing the appropriate grammatical affixes and function words, is discussed relatively extensively. For example, the authors discuss questions such as the preserved syntactic competence in agrammatism and whether or not agrammatism should be considered a coherent syndrome. The authors further try to argue that Broca's aphasia, Wernicke's aphasia, and conduction aphasia can each be linked to a particular area in the brain. If this area is injured, the result is a characteristic deficit.

    Chapter 6 is about childhood aphasia. It is basically about language acquisition and tries to make the connection to brain development in the child. The cases of Genie and other children with specific language impairment (SLI) are discussed. However, this chapter seems disconnected from the previous and the following chapter, and it is difficult for the reader to see the connection between this chapter and the rest of the volume. Maybe it would have been better to try and incorporate the facts about childhood aphasia in the previous chapters.

    The next chapter (Chapter 7) talks about damage to the right hemisphere of the brain. Since aphasic syndromes are mostly -- but not always -- tied to the left hemisphere, the book up until this chapter focused primarily on the left hemisphere. However, certain aspects of linguistic processing, such as the processing of suprasegmental structures are mainly done by the right hemisphere. Therefore, it is important to also describe the consequences of right hemisphere damage for the use of language. Some studies on discourse production of right-hemisphere patients revealed some subtle deficits in verbal pragmatic aspects; other studies showed that these patients have difficulties with non-literal, that is, metaphoric usage of language. The chapter ends with a discussion of "split-brain" patients, i.e., patients in which the connection between the two hemispheres, the corpus callosum, has been cut in an attempt to treat severe epilepsy. Because the communication between the two hemispheres is interrupted in these patients, they provide a clear case for the investigation of the language abilities of the individual hemispheres. Michael Gazzaniga has done important research on these patients and found interesting results about the abilities of the individual hemispheres.

    Chapter 8 focuses on dementia, e.g., as the result of Alzheimer's or Parkinson's disease, and its consequences for language processing. Patients with dementia experience word finding difficulties more frequently than healthy subjects. At this point, however, it is unclear whether word finding problems in Alzheimer's patients, for instance, are due to permanent loss of lexical representations or whether they are rather due to difficulty in accessing those representations. The problem of distinguishing between aphasic and demented patients is also discussed. Interestingly, the first author of this volume co-authored a paper claiming that one of the two supposedly aphasic patients presented by Wernicke in 1874 was clearly demented.

    In the next chapter, Chapter 9, specific language deficits are discussed, namely dyslexia and dysgraphia. Both are impairments involve written language processing: dyslexia is a reading deficit, and dysgraphia is a spelling deficit. Developmental dyslexia (childhood dyslexia) and acquired dyslexia (caused by brain damage) have to be distinguished because they are caused by different syndromes. Developmental dyslexia is presumably caused by the inability to fully process the phonological input at a critical period, while acquired dyslexia is due to damage to the written word processing system. Several different forms of acquired dyslexia can be distinguished: surface dyslexia, i.e., the ability to read written input only via a non-lexical route (grapheme-to-phoneme conversion), and phonological dyslexia, i.e., reading written input only via the lexical route. Typically, surface dyslexics make errors on irregular words while phonological dyslexics cannot read pseudo- words. If the semantic system in phonological dyslexics is also damaged, the deficit is referred to as "deep dyslexia". Typically, deep dyslexics make semantic errors in reading (e.g., producing "queen" in response to the written stimulus "king"). A disadvantage of an introductory volume like this is always that some issues cannot be discussed with enough depth. For example, the authors claim that processing differences between abstract and concrete words have been reported in dyslexic patients suggesting that these two types of words are organized differently in the lexicon. However, they do not say how abstract and concrete words might differ in their lexical representations. The discussion about dysgraphia is not satisfactory because it is much too short; slightly more than one page is clearly too little space for such a complex and well-studied deficit.

    In Chapter 10, the authors discuss the phenomenon of bilingualism. Of special interest to the psycholinguist is of course the question of lexical organization in the bilingual (e.g., are the two lexicons of a bilingual completely separated or are they perhaps partially combined?). Presumably, a single semantic system maps onto language- specific word forms in bilinguals. Unfortunately, the latest knowledge that we have about these questions did not make its way into this book (see latest issues of "Bilingualism: Language and Cognition", an international journal for the latest research in bilingualism). Recent experimental evidence by Costa, Miozzo, and Caramazza (1999) suggests that bilinguals, when producing speech, consider only words of the target language for lexical selection. In the chapter about bilingualism, phenomena such as code-switching and general second language acquisition abilities are also briefly mentioned.

    In Chapter 11 the authors introduce linguistic theory. In this chapter, they try to tie these linguistic theories into what has been said earlier in the volume. On the one hand, this late discussion about linguistic theory has the advantage that all the data and facts about language and the brain have already been stated and can now be set into relation with the constructs of linguistic theory. On the other hand, this is a disadvantage for those readers who may have particularly little knowledge about linguistic theory; for less knowledgeable readers, it would have been better to discuss the basic linguistic levels in the beginning.

    Finally, in the last chapter of this volume the authors make predictions about where the field of neurolinguistics will go in the future. The possible contributions and values of artificial intelligence, brain imaging, and neurophysiology are assessed, and the need for cross-linguistics studies is emphasized.

    In summary, this is a decent introductory book about the study of language and the brain. Researchers in the field of aphasiology will probably not profit very much from it because the book is too basic. For the beginning student, however, it may be an ideal introduction because a broad range of topics is covered. The historic developments and classic papers are mentioned in the individual areas of research, and further readings are suggested. The individual chapters are relatively independent of each other and can be read independently. Unfortunately, very little is said about new imaging techniques and what their merits for the field may be. Nevertheless, the book seems to be an excellent source for a quick overview of the field of neurolinguistics. The truly interesting work, however, only starts once one gets involved into more specific issues. Due to space constraints, this volume cannot serve this purpose.

    Bibliography

    Costa, A., Miozzo, M., & Caramazza, A. (1999). Lexical selection in bilinguals: Do words in the bilingual's two lexicons compete for selection? Journal of Memory and Language, 41, 365-397.

    Reviewer's biography

    >From 1994 to 1998, the reviewer worked at the Max Planck Institute for Psycholinguistics in Nijmegen, The Netherlands. In 1997, he received his Ph.D. in Psychology from Nijmegen University. In his Ph.D. dissertation, he investigated the role of the syllable in lexical access during speech production. Since March 1998, he has been affiliated with the Cognitive Neuropsychology Laboratory of the Psychology Department at Harvard University in Cambridge, MA (USA). His research interests include phonological and morphological encoding in speech production, language processing in neurologically impaired patients, articulatory-motor processes during speech production, and forensic phonetics.