by Brian B. Boycott

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This book arises from a meeting organized by the two editors in Tübingen (5-7 September 1996). It was a happy meeting with good interaction between the participants. The editors have continued their hard work by supervising most of the contributors into writing comprehensive, well-balanced articles. In my opinion, a successful effort has been made to make the papers accessible to a wider readership than is usual for the published offerings of a specialist gathering. Given the large array of techniques that today have to be mastered to do a worthwhile piece of neurobiological research, all of us, especially graduate students, are increasingly unable to find time to reach out beyond the constricted horizons of our own specialities, in short, to take a broader view. It was bold to organize a meeting spanning the genetic determination of cone photopigments in primates, their electrophysiology and evolution, on through retinal circuitry to cerebral cortical processing of chromatic signals, the interaction between color and motion in the primate visual system and to end with papers on the perception of color. The result is a welcome gathering together of diverse approaches being made to understand the neural mechanisms of color vision.

There is a tension between the increasing technical effort and specialization required in modern neurobiological research and the achievement of sufficient general understanding to enunciate basic general rules of neural functioning. About twenty-five years ago, H. B. Barlow (1972, Perception , Vol. 1, pp. 371-394) sought a "neuron doctrine for perceptual psychology." He reviewed the then available literature seeking basic formulations (dogmas) that might have the power to do for neurobiology what Crick and Watson's formulation, "DNA codes protein," has done for molecular biology. It is no criticism of the present volume to say that it would be interesting to use it to examine to what extent modern understanding of the mechanisms of color vision fits into or modifies those dogmas. Are there compelling reasons to reformulate them? To what extent does an understanding of other sensory mechanisms affect generalizations in color vision , and vice versa? For example, suppose that we now knew the neural networking for the perception of moving colored buses; would that predict the mechanisms for an equivalent auditory perception? That is a task for another place and another time, but it is worth reminding readers, especially because they are not addressed frequently, that the issues of the basic principles that Barlow raised will not go away.

While making these, perhaps rather obvious, remarks, it is also worthwhile to remind ourselves of a current great inhibition to making reductionist generalizations about central nervous systems. We are all inclined to forget, or pay only lip-service to, the fact that for most parts of the brain we do not know how many types of nerve cells we have to deal with and nothing, therefore, about what they may do to our current interpretations. For example, it is only recently that we have come to know that amacrine cells in the inner nuclear layers of monkey and rabbit retinae comprise between 28 and 35% of the population of cells. Furthermore, in rabbit retina these have been shown to constitute some 26 different morphological types of interneuron. Only for four of these types (the AII, the starburst, the indoleamine-accumulating and the dopaminergic cells) do we have evidence of what these cells do physiologically (M. A. MacNeil & R. H. Masland, 1998, Neuron , Vol. 20, pp. 971-982). The primate amacrine cell system is certainly equally complex. Furthermore, as those authors point out, the work of J. Lund and colleagues (e.g., Lund & Wu, 1997, J. Comp. Neurol., Vol. 384, pp 109-126) reveals some 50 anatomical types of local circuit neurons in the striate cortex about which we know nothing physiologically and which are hardly yet incorporated into functional models.

The need for knowledge of what structures are actually in the areas of the brain that we analyze physiologically and perceptually; the need to look for the basic rules of the operation of the neural nets that we study; both seem to me to need emphasis in a foreword to a book of papers that I hope will speed us towards an even more fundamental and general understanding of the problems that they address.

Brian B. Boycott

December 8 1998

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