Brain, Vol. 123, No. 5, 1062-1063,
May 2000
© 2000 Oxford University Press
Book reviews |
THE NEUROCOGNITION OF LANGUAGE.
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School of Psychology, Cardiff University, Cardiff, UK
The title of this book conveys its theme neatly, although I imagine there may have been considerable debate on what the best title should have been for this cross-disciplinary work. It reflects the current move away from the ultra-cognitive neuropsychology approach to language and the brain, with its highly focused emphasis on the functional basis of language disorders, and a de-emphasizing of anatomical considerations. A great many boxes and arrows were drawn on the basis of how language processing broke down after brain lesions, with only a vague idea of what they represented in anatomical terms. The reason for this was partly the lack of an animal model, which meant that research had to make use of what the editors describe as `experiments of nature' in the form of attempting to map patients' functional lesions onto anatomical lesions. This procedure was necessarily less than precise, because patients' lesions are never as neat and circumscribed as those produced with laboratory animals. However, much to the distress of some of our colleagues, advances in neural imaging technology have lead to a change in the situation. The content of this book reflects such a change.
Much of the research summarized features not only functional MRI (fMRI) and PET scanning, but also data from event-related potentials (ERP) and event-related fields (ERF), so that the temporal dimension of language processing is considered as well as the anatomical location of various processes. The book is organized into four sections, with each containing three chapters on a common theme. The introductory section opens with Brown and Hagoort's concise introduction to the area and the type of research questions that are asked. This is followed by an exceptionally clear and readable chapter on `Functional neuroimaging in cognitive neuroscience' by Michael Rugg, which I would have no hesitation in referring people to. These two chapters go very nicely together, but then the third chapter appears to be pitched at a totally different level. Ray Jackendoff's chapter on `The representational structures of the language faculty and their interactions' seems strangely placed in this section. Linguistics is undoubtedly a complex area, and perhaps explaining its concepts in simple terms is a more difficult task than I appreciate. But for an introductory chapter, this did seem very complicated, and perhaps confusing about what the immediate goals of cognitive neuroscience are. Whilst `generative grammar' is undoubtedly very important, I would have thought there are a great many other issues relating to language processing that are currently a more primary focus of cognitive neuroscience research.
The second section focuses on cognitive psychology and psycholinguistics, beginning with a chapter by Levelt describing his model of speech production. As one of the most influential models of the last 10 years, it has appeared in numerous publications and introduced to most people the concept of the `lemma', a discrete lexical representation of a word that is accessed before we activate the relevant speech sound. As you would expect, the next two chapters cover speech comprehension and reading, from a cognitive point of view, and attempt to compliment Levelt's chapter on speech production. All three chapters provide readable summaries.
Section three is entitled the `Neurocognitive architecture of language', and covers the material that I would most strongly associate with the title of this book, namely data from imaging and lesion studies. It commences with a chapter on the neuro-anatomical correlates of single-word processing, by Price, Indefrey and van Turennout, which looks at the imaging data associated with the performance of various lexical tasks. I think this chapter illustrates very nicely the kind of logic behind a great many of the studies that are currently being carried out using a subtraction method. It also illustrates that in many cases our understanding of functional neuroanatomy is not as sophisticated as our understanding of the cognitive processes that take place. However, this may reflect the difficulty involved in designing tasks that selectively tap into particular levels of processing without activating other levels of processing. An interesting example of where findings seem to conflict is given with the case of semantic processing, where neuropsychological data indicates the importance of the temporal cortex, but imaging studies point towards the left inferior frontal cortex. This may reflect an example of the difference between which areas must be activated to perform a task, and which areas commonly are activated. After this summary of imaging research, the following chapter on the `Functional and neural architecture of word meaning' unsurprisingly leans rather more heavily towards lesion data. The main focus of this chapter is whether the semantic system should be viewed as a unitary entity, or as a number of dissociable subsystems, and provides a good example of how studying the brain can inform a debate on an aspect of cognition that experimental psychology has failed to settle. The last chapter in this section comes back to syntax.
The final section is entitled `Language from a neurobiological perspective', and commences with a chapter on the anatomy of Broca's area, the region of the brain that largely started off the whole issue of localization of functions. This is followed by an introduction to the field of functional connectivity in neuroimaging. Rather than looking at dissociations, and asking which areas are activated during one task that are not activated during another, functional connectivity looks at correlations. Although this seems to represent an interesting alternative approach to imaging, I came away with the impression that there is still some way to go in developing the application of this technique. The final chapter concentrated on explaining the use of EEG, MEG and ERP.
Overall this was an interesting and enjoyable book to read. There seems to be an assumption here that many specialists in cognitive neuroscience will know little of language functions, and specialists in language and linguistics will know little of its neural basis. One of the aims of the book is to provide such investigators with an overview of aspects with which they may be less familiar, and it largely makes a good job of it. The chapters are (almost) all accessible, and provide neat summaries of their particular topics. I was half expecting there to be a final summarizing chapter at the end, talking about future research directions, but perhaps this is not necessary. So the question is should this book find its way into your library? I would suggest the answer is yes. It largely provides concise summaries of cutting edge research issues, which I can see myself dipping into again.
Notes
Edited by Colin M. Brown and Peter Hagoort. 1999. Oxford: Oxford University Press. Price £49.50. Pp. 424. ISBN 0-19-852448-X.
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