Introduction to brain topography

Electroencephalography and cfinical Neurophysiology, 83 (1992) 91-92

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© 1992 Elsevier Scientific Publishers Ireland, Ltd. 0013-4649/92/$05.00

Book Reviews

edited by E. Niedermeyer and P.M. Rossini New antiepileptic drugs (Epilepsy Res., Suppl. 3). - F. Pisani, E. Perucca, G. Avanzini and A. Richens (Eds.) (Elsevier Science Publishers, Amsterdam, 1991, 212 p., U.S. $128.00, ISBN 0-444-81392-6)

New Antiepileptic Drugs is an interesting addition to the epileptologist's library. T h e book attempts to provide an update on the status of new anticonvulsants in 195 pages that are divided into 5 sections containing a total of 27 chapters. Section 1, "general aspects," contains only two short chapters and falls short of the aim, stated in the book's preface, to account for the size of refractory epilepsy and its related problems. However, the two chapters are well written and introduce the difficulties of assessing the intellectual and long-term effects of uncontrolled seizures. T h e book's second section, "experimental aspects," has 5 chapters and provides a good overview of issues related to epilepsy research. A chapter by Avanzini and Marescaux is particularly good in its review of animal models available for non-convulsive epilepsy research. Missing from this book is a comparable chapter on animal models available for convulsive epilepsy investigations. C h a p m a n and Meldrum provide an excellent update on excitatory amino acids and their role in epilepsy, as do De Saro et al. for calcium antagonists. Section 3 contains 3 chapters on "clinical aspects." Dieter Schmidt begins with a very good review of clinical drug trials and this chapter is worthwhile reading for anyone involved in clinical epilepsy research. This section would have benefitted from a chapter dedicated to clinical trial design with an introspective look at possible guidelines for research standardization. A chapter on the value of video monitoring and other new technologies available for clinical research might also have been valuable. " T h e new antiepileptic drugs" section is the core of this text and examines the available data on 13 anticonvulsants. In general, each chapter is well written using a similar format which is easy to read and makes comparisons between drugs easier. Missing from this section is a chapter on the phenytoin prodrug, ACC-9653, which, though the drug itself is not new, the formulation is, and therefore, I believe, merited recognition. T h e last section, "recent clinical trials," is limited in its scope. The first chapter is on carbamazepine-10,11-epoxide, which was not presented in the book's previous section on new antiepileptic drugs, and I am not sure why it was included in this section. The other 3 chapters in this section provide capsule summaries on the clinical trials on gabapentin, lamotrigine, and vigabatrin in which the authors present limited data making the reader d e p e n d e n t on their conclusions. Overall, New Antiepileptic Drugs is a valuable book that updates the new anticonvulsants and is worthwhile reading for anyone involved in epilepsy research and interested in staying current with this exciting field.

Silvana Riggio

Medical College of Pennsylvania, Philadelphia, PA (U.S.A.)

Introduction to brain topography. - by P.K.H. Wong (Plenum, New York, 1991, 255 p., U.S. $45.00) The publication of this book on brain topography is a welcomed addition to this controversial field. At present, the field consists mainly of a few review articles, small sections of books and two other volumes with many short chapters of work in progress, in addition to original articles. The reader interested in contributing to the field will welcome Dr. W o n g ' s book as a proper introduction to the field. Part I is on " f u n d a m e n t a l s " and illustrates well the "alias" error with regard to sampling rate. Analog-digital conversion precision is also well described, relating the selection of step size to amplifier noise. The reader is led by the hand, step by step, through the construction of a brain map, although linear vs. non-linear interpolation could be somewhat expanded. Here and throughout the book, the author utilizes 3-dimensional line figure displays as an attractive, intriguing and informative way to represent data. The effect of the n u m b e r of electrodes in an array is made clear by excellent illustrations, as is the change in the reference electrode. The well-known Hjorth or source derivation procedure is briefly described and saturation from high gains is well displayed. In this chapter Dr. Wong gives the reader a useful but brief guide for a clinical interpretation of brain maps by pointing out the primary, secondary and tertiary features that need attention. The reader may be disappointed if the expectation is to be led by the hand for further instruction as to how to interpret these maps, since the majority of the rest of the book deals with fundamentals and principles. For example, an excellent discussion can be found for apparent m o v e m e n t of a spike focus, but no discussion about how one may identify such a focus. O n e minor problem at this point in the book is that there are so many large figures, at times with information that could have been minimized, that the text may be 17 pages ahead of the figure. Source modelling and analysis is the topic for part 2 and deals clearly with both the well-known forward and inverse solution. This reviewer appreciated the clarity of all steps followed in the dipole localization method, including the question of "goodness of fit." The reader may be surprised that part 3 is on magnetoencephalography, since the book is on brain topography. The author can likely justify its presence there, especially since Dr. H. Weinberg was an influential colleague and likely contributed to this part. The discussion and descriptions are well done except that the reader may initially be confused by "for magnetic signals the strength falls off as the cube of the distance" (p. 114) and "the field falls off as the square of the distance of the sensing coil from the source" (p. 116). O n e of the best figures in the book is on information processing from short-latency brain-stem responses within 6 msec to the PINV response at 2 sec. The penultimate section on statistical approaches will not be easy for most readers, but these discussions are important in dealing with topographic mapping. Even the "Mahalanobis distance" is briefly discussed but this reviewer would have welcomed further clear exposition on this technique used for computerized correlations. The advice on disregarding the Bonferroni approach is sound and should be understood by all. Although Dr. Wong is accurate in his statistical

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BOOK REVIEWS

discussion, most readers will definitely find this chapter difficult. The last part is called "selected normative data," but unfortunately cannot be used by readers for clinical studies. O n e small problem is Figs. 5-2 and 5-3 are reversed in their legends. The one last part of the book is a reference section with 42 pages of references as testimony for the work that Dr. Wong has put into this book, Although a n u m b e r of typographical errors are found in this book, the author has presented a sound volume on the important fundamental principles of brain topography. The reader who expects to read it and immediately interpret maps correctly will soon learn that the book represents the tools that need to be understood before proceeding with careful data collection and experience. Dr. Wong should be congratulated for this fine effort. John R. Hughes

University of Illinois Medical Center, Chicago, IL 60612 (U.S.A.)

Digital biosignal processing. - R. Weitkunat (Ed.) (Elsevier Science Publishers, Amsterdam, 1991, 400 p., Price: hard cover U.S. $274.50, paperback U.S. $80.00, ISBN 0-444-81140-0)

Digital Biosignal Processing, edited by R. Weitkunat, is very definitely not a reference book or comprehensive treatise for the cognoscente of DSP. What it is, however, is a very thoughtful primer which uses simple explanations and appropriate metaphors to help the reader gain a clear understanding of the many facets of signal processing. Although the title uses the word "biosignal," the book is specifically oriented towards signals from the neurosciences, in both the selection of examples and the focus of the explanations. Although many neuroscientists are concerned fundamentally with electrical neural signals, the interests of others who are concerned with images and signals transduced from other modalities are also addressed in this book. For the most part, the book is written from a non-engineering standpoint, and the strength of the book is its clear and simple explanations. The book attempts to at least mention virtually all of the areas of signal processing with which the reader might come in contact. It covers, for instance, even the rather extravagant field of chaos. Discontinuous signals, specifically point processes indicating occurrence times, are also touched on. T h e editor seems to have exercised quite good control over the authors in an effort to maintain consistency and to provide continuity. There is a painstaking and successful effort not to overwhelm the reader, accomplished in part by limiting coverage of each subject. For example, only 3 window types are applied to Fourier transformation, and only a relative handful of different types of analog to digital routines are discussed. As another example, the principles and application of digital filters are discussed, but no information is

provided about digital filter design. In some cases the explanations ended up being excessively brief (for example in the section on analog signal conditioning). Overall, however, the authors achieve quite a good balance, i.e., covering enough material beyond the simplest case, but not going to the extreme of attempting to be all-inclusive. The book is packed with special items highlighted with "bullets" to emphasize key points, as well as with side-bars to provide concise "'short takes." The actual practicality of the examples varies, but there are consistently enough examples to enhance the reader's understanding. Although snippets of computer code are included for illustration, the book wisely steers clear of the cookbook approach. At the risk of becoming quickly obsolete, this volume also names vendors and products. This provides the reader with at least a concrete starting place for several projects. Many readers will find the sections on learning irrelevant to their work and the techniques (e.g., behavioral shaping automata) unconnected to their usual concept of digital signal processing. Although the relationship of behavior to biosignals is perhaps a leap and at times an unsubstantiated example, these aspects reflect the interests of the editor and several of the authors, and, importantly, they do not detract from the fundamentally good digital signal processing material. The only chapter which appears to be somewhat weak and disjointed is the one on image processing. Perhaps this chapter suffers because it stands alone, and the book might well have done without it. T h e chapter on neural networks is a wonderful introduction to the field. It takes a highly sophisticated and difficult area, and makes it quite understandable. This chapter, however, never gets to the application of neural networks in conventional one-dimensional signal digital signal processing; rather, it employs character recognition examples, The book also suffers at times from some spelling and grammatical errors, but these are relatively minor. The authors are quite forthright in their purpose of not attempting to cover every aspect of digital signal processing comprehensively. Almost all of the authors do an excellent job of clearly communicating their ideas, with the level of detail and understandability depending to a certain extent on the individual author. This book succeeds amazingly well in providing a solid introduction to digital signal processing, while nicely straddling the chasm between the strictly engineering approach and the laboratory cookbook. The book is available from Elsevier in both Europe (P.O. Box 211, 1000 A E Amsterdam, The Netherlands) and the U.S.A. (P.O. Box 882, Madison Square Station, New York, NY 10159). It is priced fairly at 80 U.S. dollars (paperback) and is a good investment for the neuroscience investigator who wants to be prepared to move into the 2lst century. Richard C. Burgess

Clereland Clinic Foundation, CTeceland, OH 44106 (U.S.A.)