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Book Review - Neurons and Networks
Neurons and Networks
by John E. Dowling
Harvard University Press, 2001
Review by Bill Seeley
Nov 12th 2002

John E. Dowling, in the preface to the second edition of Neurons and Networks:  An Introduction to Behavioral Neurosciences, describes behavioral neuroscience as the integration of three previously distinct fields: neuroanatomy, the study of the structure of neural tissue and cells; neurophysiology, the study of the function of neural tissue and cells; and neurochemistry, the study of the composition of neural tissue, cells, and the substances that regulate their interactions.  Dowling argues that facts concerning the origin of our understanding of synaptic transmission among neurons illustrates the close integration of these fields in explanations of brain function.  Dowling in turn uses the practical integration of these fields to generate an easily understood model for understanding brain function and the ways in which behavior emerges from information processing in the brain.  As each chapter unfolds he provides a detailed account of the symbiotic relation between our understanding of the anatomical structure and physiological function of the brain, laying out the logic of brain function in a clear and concise manner. 

Neurons and Networks is designed as a textbook for an introductory undergraduate course in behavioral neuroscience.  But it is also offered as an introductory resource for a general audience.  As a result it is readily accessible to an audience with a minimal background in biology, chemistry, and physics.  I found Dowling's style straightforward and enjoyable to read, and the content of the diagrams and examples clear-cut and informative.

The book is divided into three sections:  Cellular Neuroscience, Systems Neuroscience, and Cognitive Neuroscience.  The first section details the manner in with the structure and function of nerve cells determines the way the brain receives, carries, and transmits information.  The second examines how behavior emerges from particular neural processing systems in both vertebrate and invertebrate animals.  The third section examines the neural underpinnings of higher-level mental functions, e.g. perception, language, memory, emotion, motivation, and consciousness.  Dowling's own work focuses on the retina's role in visual processing.  As a result the book leans heavily on examples from the visual brain.

The model for Dowling's integrative approach, as mentioned above, is derived from the structure of advances in the understanding of basic synaptic transmission.  Early in the twentieth century it was proposed that chemical interactions drove synaptic transmission.  But, Dowling explains, it was two discoveries in the mid-Fifties that provided the foundation for the understanding of these processes: a) neuroanatomical studies employing electron microscopy revealed the presence of small vesicles in nerve terminals adjacent to synaptic junctions; and b) neurophysiological studies employing intracellular electrical recording revealed electrical responses in post synaptic cells.  The newly discovered anatomical structures suggested a mechanism to explain these physiological findings and the physiological findings in turn indicated a function for the newly discovered anatomical structures.  Later, in the 1970s, advances in neurochemistry provided an explanation of the mechanisms regulating synaptic transmission, i.e. the mechanisms subserving the function of the anatomical structure of the brain.

This integrative model is applied at many levels throughout the book.  Each chapter can be broken down into an examination of the interplay of the anatomy and physiology of a particular cellular process or neural system.  Likewise, the general structure of the book is an examination of the manner in which cellular structure and biological function integrate to give rise to more complex computational behavior.  As a result, higher cognitive functions indicative of what we ordinarily refer to as "mind," or "consciousness" can be explained by, and so by implication are interpreted as, the product of the integration of the basic biological structures and processes of complex computational systems in the brain.

Dowling explains the visual system in great detail.  Neurons and Networks devotes five chapters to vision.  The processing of visual information is followed from the manner in which the retina gathers information concerning lightness intensity from the environment to the re-construction and segregation of information concerning color, form, and motion by areas V2, V4, V5, and V8.  In contrast, the textbook includes only single chapters on language, emotion and rationality, and learning and memory respectively. 

Dowling's rationale for this division of labor is twofold.  On the one hand, the visual perceptual system is the most comprehensively understood cognitive system in the brain, and the primary sensory areas of all five sensory modalities exhibit the same structure as the primary visual cortex.  For instance, the cells of the primary somatosensory and auditory cortex exhibit columnar organization as do those of the primary visual cortex.  The receptive fields of the tactile neurons of the primary somatosensory area exhibit direction sensitivity like the orientation selective cells of the primary visual cortex.  These cells may also exhibit a similar antagonistic center-surround organization.  Furthermore, the columns of the primary auditory cortex are grouped according to the relative similarity of their receptive field properties, e.g. tonal frequency, as are the orientation selective cells in the primary visual cortex.

But more importantly, the visual system provides a clear and concise example of the integrative model for neuroscience that Dowling prefers.  The anatomical structure of the visual system is a clear consequence of, and so is explained by its physiological function, and the physiological function of discrete parts of the visual system are explained by their anatomical structure, e.g. the hypercolumns of primary visual cortex of V1 which comprise its smallest functional component. 

Lord Kelvin famously claimed that he could not understand a phenomenon until he could provide a mechanical model explaining how it occurred.  Mental phenomena have often been held to be uniquely impervious to this sort of mechanistic explanatory model.  But advances in neuroscience over the last half century have slowly chipped away at the ephemeral facade of the ghostly appearance of mentality, revealing its more tangible physical and computational foundations.  Dowling's clear and careful explication of the integrative approach of behavioral neuroscience demonstrates how an understanding of the structures and processes of the brain informs our understanding of mental processes from basic motor skills to the complex relationship between emotions and rationality.  As a result, Neurons and Networks serves as a readily accessible introduction to the methods, results, and explanatory power of this burgeoning field.


© 2002 Bill Seeley


Bill Seeley is a doctoral candidate in the Program in Philosophy at CUNY - The Graduate Center working on the neurophysiology of aesthetic perception. He also has an M.F.A. in sculpture from Columbia University. His work has been exhibited in New York City, at Yale University, and at The Addison Gallery of American Art in Massachusetts. He teaches ethics and aesthetics at Hofstra University.