Last year marked the 400th anniversary of the King James Version (KJV) of the Holy Bible. Arguably the most influential book in history, the KJV was nonetheless revised in 1881, a clear indication that no book is too definitive, no author too omniscient to escape posterity’s occasional editorial polish. So it goes in neuroscience, where 2012 will see the fifth edition of Principles of Neural Science (the KJV of the CNS) and From Neuron to Brain. Ionic Channels of Excitable Membranes has exhibited a more stable conformation, having undergone only two revisions since its debut in 1984, but it seems inevitable that channel biophysics will some day be known as the Field of Seven Hilles. Relatively speaking, then, a second edition of The Retina, John Dowling’s paean to “an approachable part of the brain” that was first published in 1987, is long overdue. In the preface to the original, which marked his first 25 years in the field, Dowling predicted another exciting quarter century of progress in retinal research. This year, Dowling has delivered his implicitly promised update with the Revised Edition of The Retina (The Belknap Press of Harvard University Press).
If The Retina truly is the Bible of retinal neuroscience, then Dowling naturally assumes the role of Moses, the Almighty’s Pentateuch coauthor. Appropriately, perhaps, the new edition is simply Revised, forsaking the typically ordinal lineage of academic texts and possibly portending a New Revised Standard Edition in the far distant future. (Moses did, after all, live to be 120.) Although Dowling certainly helped lead the field through the Wilderness to a vibrant multidisciplinary promised land flowing with ideas and grant money, his greatest contributions may identify him more with Abraham, who fathered a great nation. In the preface, Dowling graciously acknowledges his own nation of students, fellows, and collaborators who have gone forth and multiplied, populating the world of retinal neurobiology. Accordingly, work published by his legion of progeny dominates the text and figures.
The scriptural analogy may be a bit misleading, because neither version of The Retina claims ultimate authority. In his new preface, Dowling reiterates his original disclaimer that he purposely limited the scope of the book to make it, well, more approachable. (Although 25% longer than the original, the Revised Retina weighs in at just 355 pages, a mere pamphlet compared to Principles of Neural Science.) With anecdotal and occasionally first-person prose, The Retina reads less like a reference work and more like a collection of carefully crafted lectures or, given Dowling’s explicit emphasis on his own research interests, a scholarly memoir.
In this age of Wikipedia and mini-Ted talks, The Retina discourages the reader from simply scanning its text for some particular factoid, inviting you instead to sit and stay awhile, to turn off your smart phone, and listen to a good story. I often open to the middle of a chapter, only to find myself reading to its end and then turning to the beginning until I come to the place where I started, a good half hour well spent. The monochromatic pages (notwithstanding a small clutch of color plates) in the Revised Edition harken back to the good old days of pen plotters and slide carousels, when retinal research was rendered in camera lucida drawings, electron micrographs, and oscilloscope traces on the undersized ivory pages of the Journal of Physiology. On the other hand, Dowling himself observes that “color enriches our world tremendously,” and many advances in modern retinal neuroscience concern, exploit, or would be presented more effectively in color.
The first five chapters have been revised to varying extents but retain the same general structure and content of the original. Chapter 1 remains a nice overview of the retina’s evolutionary diversity and developmental complexity, stating the case for the retina as a model system for brain development and function. Chapters 2–5 survey the different cell types in the retina, their connectivity to one another, their responses to light stimulation and cellular mechanisms of synaptic transmission and neuromodulation. Each chapter follows the same rough outline, beginning with photoreceptors and ending with ganglion cells, enabling the new reader to incorporate each concept into an integrated understanding of the entire circuit.
Chapter 6 reprises a thorough discussion of photoreceptor transduction and adaptation, ending with a section on network adaptation that could have paid greater attention to synaptic/network adaptation mechanisms studied recently by Rieke, Demb, and others. A nice new chapter on color vision includes sections on visual pigment genetics and color processing circuitry, and the original chapter on electroretinograms and glia has been expanded to include nutritional and inherited retinal degenerations.
The Revised Retina, like the original, closes with a chapter in which Dowling addresses “what these studies in the retina tell us about brain mechanisms and function.” This is a very important section of the book because it invites retinal neuroscientists to consider the influence of their work on the broader field of neuroscience, and vice versa. The chapter remains focused on the retinal side of this equation, however, with several missed opportunities to draw interesting connections to other systems. For example, the elegantly studied local dendritic processing in starburst amacrine cells, now known to underlie directional selectivity, laid a foundation for recent studies of dendritic computation in cortical pyramidal neurons (e.g., Branco et al., Reference Branco, Clark and Häusser2010). And, while few neurons elsewhere in the brain may signal exclusively via slow graded membrane potentials, many of them appear to transmit analog signals via small sustained depolarizations in addition to their “digital” spike trains (e.g., Alle & Geiger, Reference Alle and Geiger2006; Shu et al., Reference Shu, Hasenstaub, Duque, Yu and McCormick2006; Christie et al., Reference Christie, Chiu and Jahr2011).
Critiquing Scripture is a risky business, to be sure. Having had The Retina placed into my hands early in my scientific childhood, perhaps I had grown to anticipate that its second coming would provide all the answers—an unreasonable expectation, especially given that the last 25 years have seen the retina literature triple in size. Free of the obligation to provide a comprehensive survey, The Retina remains a compelling read and an admirable labor of love by one of the field’s true apostles.
