nature neuroscience • volume 3 no 8 • august 2000 753

Dendrites are among the most extraordi-nary and visually compelling structures inthe nervous system. Purkinje observedthem as early as 1837, and Deiters beauti-fully depicted them in his drawings of indi-vidual dissected motoneurons in 1865.Wilhelm His coined the name ‘dendrite’ in1890, only 7 years before Charles Sherring-ton first used the term ‘synapse’. By thenCamillo Golgi had invented his eponymousstain, which casts in exquisite silver sculp-tures the finest ramifications and process-es of neurons. Golgi’s discovery enabled hisrival, Santiago Ramon y Cajal, to defineneuronal circuits of retina, cerebellum andspinal cord, based on the inspired assump-tion that information was transferred fromdendrites to the cell body and thence downthe axon to synapses on dendrites. Thus,from the earliest decades of modern neu-roanatomy and neurophysiology, dendritesand synapses were intimately linked. Theyremain so today, agree the authors of Den-drites, a cross-section of the state of the artin 14 chapters contributed by 19 authors.

Why mention these ancient observa-tions when reviewing a book about workusing the latest techniques—patch-clamprecordings, optical imaging of ion con-centrations and molecular probing of pro-teins and RNAs—which promise torevolutionize the study of dendrites? Theanswer is that chapter after fascinatingchapter makes it evident that nothing onthe horizon, either technically or concep-tually, will solve the mysteries of dendrit-ic function in the way that a singletechnique, Golgi’s stain, did for structure.

These early structural studies first raisedthe central question repeated here by theeditors: why is dendritic structure so enor-mously variable? The equally long-stand-ing speculation is that this variability isfundamental to dendritic function. If so,then we can expect no unified view of den-

of spiny dendrites, and most excitatorysynapses are formed with them. Thus,spines are a point of convergent interestsof synaptic physiologists, anatomists, neu-rochemists, molecular neurobiologists andtheoreticians. A variety of roles in devel-opment, plasticity and computation havebeen proposed for them, but their func-tions remain a mystery. Recent technicaladvances in light microscopy, however,have enabled scientists to observe thegrowth of new spines in response tochanges in dendritic activation, offering anew means of relating dendriticmicrostructure to learning and memory.

Most of what we now think about thefunction of dendrites arises not from exper-imental observations, but from theory. Thismakes dendrites special, as there are fewother areas of neuroscience where experi-mentalists must rely so much on theoreti-cal work. It is thus fitting that, although theaims and future interests of its manyyounger contributors are well represented,Wilfrid Rall’s contribution, at age 77, lies atthe center of Dendrites, both literally andintellectually. His chapter is delightful, notonly because it links the generations, butalso because he was the source of manymodern ideas of dendritic function. Rall’sapplication of cable theory to neurons inthe late 1950s fundamentally revised phys-iologists’ view of dendrites. Rall workedwith and inspired generations of physiolo-gists and theoreticians, many of whom con-tribute directly or indirectly to Dendrites.These researchers have now laid out a basicframework for interpreting physiologicaldata, which may be the nearest we ever getto a Golgi stain for dendritic function.

The editors sum up four key areas forfuture development. The fourth is surely themost important: “a better understanding ofthe relationship between individual featuresof dendrites and higher-level function.” In1943, McCulloch and Pitts discovered thatextraordinary computational richness canarise from networks of simple linear thresh-old neurons without dendrites. The Purkin-je cell illustrated on the dust jacket begs usto explain what computational advantagesaccrue by adding dendrites. The truth is wecannot yet answer the simple question ofwhether dendritic geometry, together witha given synaptic input, implements specificcomputations, or whether the specific loca-tions of synapses are largely irrelevant, anddendrites exist in a variety of forms simplyto connect to a similar variety of incomingaxon geometries. Dendrites certainly receivesynaptic inputs, but the question remains,do they really process them? Many of theauthors of Dendrites intend to find out.

A Golgi stain for dendritic function?Dendrites

Edited by Greg Stuart, Nelson Sprustonand Michael HausserOxford University Press, 1999. $55.00hardcover, pp 369ISBN 0-19-850488-8

Reviewed by Kevan Martin

drites to emerge, because the particulari-ties of the network containing the dendriteswill determine their structure and func-tion. Thus unless we understand the net-work, we should not expect to understandthe functions of particular dendrites, letalone the reasons for the wide variety ofdendritic structures. We should not expectto define a canonical dendrite, a single rep-resentative of all the varieties so fardescribed, or suppose that results found forone dendrite are necessarily generalizable.The new techniques also evidently meanthat relatively little of the structural het-erogeneity will be investigated at a func-tional, biochemical or molecular level.Already most explorations of dendrites,experimental or theoretical, are of partic-ular dendrites of particular neuronal sub-types in just three brain regions. Ironically,we understand vastly more of the varietiesof function of the products of the worm,fly and human genome than we do of thefunction of the varieties of neuronal den-drites that we suppose to be so fundamen-tal in cognition. In the next decades, wewill surely discover a great deal about theproperties of apical dendrites of pyramidalcells in hippocampus and in neocortex,and of the elaborate dendrites of cerebel-lar Purkinje cells, but the function of thevast majority of structurally distinct den-drites will (sadly) remain unexplored.

One particularly eye-catching structureappears frequently in Dendrites’ illustra-tions, a miniscule process that bristles inmultiple forms from the surface of manydendrites. The reality of these dendriticspines, a few microns in size, was initiallyin doubt. They could be artifacts, “theresult of tumultuous precipitation of thesilver” wrote Ramon y Cajal in his firstreport of his work with Golgi’s new stain,but their constancy from experiment toexperiment, “inclines us to judge that this isthe normal condition.” The electron micro-scope allowed later generations to confirmRamon y Cajal’s insight that spines werethe specialized sites for synapses. Spinescontribute half or more of the surface area

book review

Kevan Martin is at the University/ETH Zurich,Institute of Neuroinformatics, Winterthurerstr. 190, 8057 Zurich, Switzerland.e-mail: kevan@ini.phys.ethz.ch

© 2000 Nature America Inc. • http://neurosci.nature.com©

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