Brain, Vol. 122, No. 10, 2000-2002,
October 1999
© 1999 Oxford University Press
Book Reviews |
VISION RESEARCH: A PRACTICAL GUIDE TO LABORATORY METHODS.
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Optometry and Vision Sciences, Cardiff University, Cardiff, UK
One thing that is remarkable about this book is that no one has tried to produce a similar one before. Vision research is essentially a multidisciplinary activity embracing many aspects of science and technology. In the past, seminal contributions have arisen from individuals who had a fortuitous combination of knowledge, or from cross discipline co-operation. There has long been a need therefore for a basic text, which should provide an introduction to this multifaceted subject. Carpenter and Robson have attempted to fulfil this need with the co-operation of a dozen established researchers in the field. What they have provided is inevitably not a complete solution. It is, nevertheless, a book, which, to the beginner, is an invaluable source of information and to the experienced researcher is a reliable reminder of many of those things which one once knew but has temporarily forgotten or just neglected to learn.
In the first chapter Makous reviews applications of optics and photometry, describing a useful range of components and techniques. Many relevant concepts, including transfer functions, Maxwellian view systems and optical relays are introduced and useful advice is given on divers aspects including the alignment of prisms and lenses, and checking linearity of photometric systems, particularly where flashes of light of short duration are concerned.
In the second chapter, J. G. Robson provides an interesting review of light sources, which includes useful comments on the operation of the troublesome xenon flash tube, and the properties of light emitting diodes and ferroelectric shutters to provide visual stimuli. This is followed with a chapter by Tom Robson, which is devoted to topics in computerized visual stimulus generation. Starting with some fundamental aspects of visual stimulus generation based on cathode ray tube technology, the discussion proceeds to finally enable the reader to understand how spatial pattern stimuli with the best control of temporal dimensions can be generated in the computer and displayed on video monitors.
Colour specification generation and measurement are discussed in the fourth chapter by Mollon. The reader is reminded that advancing knowledge on the polymorphism of human colour vision tends to favour a method of exact radiometric specification of colour stimuli, but attention must be given to the CIE (Commission Internationale de l'Eclairage) system of colour specification which is briefly and elegantly introduced. This is essential since colorimetric and much of the psychophysical literature on colour vision is based on this system. Mollon also describes the chromaticity diagram of McLeod and Boynton, which is less arbitrary and more physiologically based, before turning to a review of instrumentation. Colour stimulation techniques, including the use of monochromators interference filters, colour video stimulators and digital micromirror devices, are described with many relevant and insightful observations.
Psychophysical methods are described by Farrel and Pelli in a refreshingly short but usefully informative chapter which introduces fundamental concepts including two alternative forced choice (2AFC) paradigms and receiver operating characteristics functions. These methods mainly relate to human subjective techniques but in the following chapter, Blake extends the application of psychophysical approaches to other species in an account of behavioural methods of analysis applied to animal vision. Many nuances of behavioural techniques of shaping and harnessing animal behavioural responses to yield statistical data are revealed with appropriate caveats on the ethical aspects of animal maintenance and training.
In a logical progression through the text, the next chapter by Atkinson and Braddick applies the concepts of behavioural observation to the investigation of vision in infancy, most notably in the application of preferential looking (PL) techniques. A few decades ago, quantitative assessment of vision in infancy was almost non-existent, but today it is virtually as precise as in mature subjects and the authors have drawn from their long and highly significant experience in this field to present a balanced account of subjective and objective methods. Techniques of photorefraction are described. They also include much useful introductory advice on the general operation of facilities for visual investigation in infancy. Currently, for PL they recommend a 2AFC staircase with three reversals, converging on the 71% probability level as the best compromise, which they have validated by extensive studies. They also comment, intriguingly, on the possible development of four position PL displays, which could dramatically enhance the speed of investigations due to the reduction of chance probability levels.
Gross potential recording methods in ophthalmology is the subject of an excellent chapter by Spekreijse and Riemslag. This is the lengthiest and certainly one of the richest sources of information in the book, perhaps not surprisingly in view of Spekreijse's long-standing role as chief editor for the periodical Vision Research and the experience of the authors in operating what is probably the most innovative laboratory of its type in Europe. The chapter deals with many aspects of surface electrophysiology, which, irrespective of the title, are by no means confined to clinical investigation. The principles for acquisition, processing and interpretation of electroretinograms electro-oculograms and visually evoked potentials are described and clearly illustrated with examples from many of the classical papers of the Amsterdam group and perhaps also from some newly conducted experiments. The authors emphasize the advantages of combining the findings from electrical and magnetic topography of scalp potentials in order to achieve a more comprehensive picture of activity in the numerous visual areas of the cortex. The findings are further validated by correlation with brain imaging techniques in selected examples.
The penultimate chapter is concerned with eye movement recording. In a scholarly review, Collwein explains that after a century of hard copy recording, digital storage and processing of eye movement data are now considered essential. Because of the widespread connections of eye movement control systems in the brain, these techniques find many applications in brain research and clinical investigations. Systems are broadly classified according to their ability to record eye position in the head of the observer, or in physical space. Immunity to translatory movements of the head and, perhaps more importantly, the eye within the orbit is a valuable property. Binocular recording is frequently invalid due to failure to satisfy the latter requirement. Numerous techniques using video imaging of Purkinje images are described, together with fundus tracking and search coil techniques.
The final chapter by Judge is concerned with the measurement of pupil and accommodative responses. Systems based on the Scheiner disc and retinoscopy principles are discussed. Here much useful advice is given on safety calculations. If experimental rather than commercially developed systems (in which invisible radiation at 850–900 nm might be accidentally focused on the retina) are to be constructed and on an occasional basis then the importance of this cannot be over-emphasized. Sophisticated systems are described.
In summary, this book provides much multidisciplinary, conventional wisdom on vision research techniques, interspersed here and there with interesting ideas of a more original nature. There is some overlap between chapters, but this is advantageous since each one can stand on its own. Inevitably, it is not an exhaustive survey. The reader will search in vain for examples of emission spectra of the phosphors of colour video monitors and also, surprisingly, for the corresponding absorption spectra of the different visual pigments in human, vertebrate or invertebrate eyes which might be excited by such stimuli. This basic information is useful in many experimental designs and may perhaps appear in a future edition. It should be appreciated that, while the book provides much introductory information, it does not equip the reader safely to embark on all the techniques it describes without some technical assistance or a period working with experienced researchers in another laboratory. Nevertheless, it is an unprecedented source of basic information and will be an asset to many vision scientists, whether involved at undergraduate level or in frontline research on the visual system.
Notes
Edited by R. H. S. Carpenter and J. G. Robson. 1998. Pp. 310. Oxford: Oxford University Press. Price £29.95. ISBN 0-19-852319-X.
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