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.

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