Introduction

More than 90% of this book is taken up by Part III, which, in 285 separately authored articles, covers a vast range of topics in brain theory and neural networks, from language to motor control, and from the neurochemistry to the statistical mechanics of memory. Each article has been made as self-contained as possible, but the very breadth of topics means that few readers will be expert in a majority of them. To help the reader new to certain areas of the Handbook, I have prepared Part I: Background and Part II: Road Maps. The next few pages describe these aids to comprehension, as well as offering more information on the structure of articles in Part III.

Part I: Background: The Elements of Brain Theory and Neural Networks

Part I provides background material for readers new to computational neuroscience or theoretical approaches to neural networks considered as dynamic, adaptive systems. Section I.1, “Introducing the Neuron,” conveys the basic properties of neurons and introduces several basic neural models. Section I.2, “Levels and Styles of Analysis,” explains the interdisciplinary nexus in which the present study of brain theory and neural networks is located, with historical roots in cybernetics and with current work going back and forth between brain theory, artificial intelligence, and cognitive psychology. We also review the different levels of analysis involved, with schemas providing the functional units intermediate between an overall task and neural networks. Finally, Section I.3, “Dynamics and Adaptation in Neural Networks,” provides a tutorial on the concepts essential for understanding neural networks as dynamic, adaptive systems. We close by stressing that the full understanding of the brain and the improved design of intelligent machines will require not only improvements in the learning methods presented in Section I.3, but also fuller understanding of architectures based on networks of networks, with initial structures well constrained for the task at hand.

Part II: Road Maps: A Guided Tour of Brain Theory and Neural Networks

The reader who wants to survey a major theme of brain theory and neural networks, rather than seeking articles in Part III one at a time, will find in Part II a set of 22 road maps that, among them, place every article in Part III in a thematic perspective. Section II.1 presents a Meta-Map, which briefly surveys all these themes, grouping them under eight general headings:

Grounding Models of Neurons and Networks

Grounding Models of Neurons

Grounding Models of Networks

Brain, Behavior, and Cognition

Neuroethology and Evolution

Mammalian Brain Regions

Cognitive Neuroscience

Psychology, Linguistics, and Artificial Intelligence

Psychology

Linguistics and Speech Processing

Artificial Intelligence

Biological Neurons and Networks

Biological Neurons and Synapses

Neural Plasticity

Neural Coding

Biological Networks

Dynamics and Learning in Artificial Networks

Dynamic Systems

Learning in Artificial Networks

Computability and Complexity

Sensory Systems

Vision

Other Sensory Systems

Motor Systems

Robotics and Control Theory

Motor Pattern Generators

Mammalian Motor Control

Applications, Implementations, and Analysis

Applications

Implementation and Analysis

This ordering of the themes has no special significance. It is simply one way to approach the richness of the Handbook, making it easy for you to identify one or two key road maps of special interest. By the same token, the order of articles in each of the 22 road maps that follow the Meta-Map is one among many such orderings. Each road map starts with an alphabetical listing of the articles most relevant to the current theme. The road map itself will provide suggestions for interesting traversals of articles, but this need not imply that an article provides necessary background for the articles it precedes.

Part III: Articles

Part III comprises 285 articles. These articles are arranged in alphabetical order, both to make it easier to find a specific topic (although a Subject Index is provided as well, and the alphabetical list of Contributors on page 1241 lists all the articles to which each author has contributed) and because a given article may be relevant to more than one of the themes of Part II, a fact that would be hidden were the article to be relegated to a specific section devoted to a single theme. Most of these articles assume some prior familiarity with neural networks, whether biological or artificial, and so the reader new to neural networks is encouraged to master the material in Part I before tackling Part III.

Most articles in Part III have the following structure: The introduction provides a nontechnical overview of the material covered in the whole article, while the final section provides a discussion of key points, open questions, and linkages with other areas of brain theory and neural networks. The intervening sections may be more or less technical, depending on the nature of the topic, but the first and last sections should give most readers a basic appreciation of the topic, irrespective of such technicalities. The bibliography for each article contains about 15 references. People who find their favorite papers omitted from the list should blame my editorial decision, not the author's judgment. The style I chose for the Handbook was not to provide exhaustive coverage of research papers for the expert. Rather, references are there primarily to help readers who look for an introduction to the literature on the given topic, including background material, relevant review articles, and original research citations. In addition to formal references to the literature, each article contains numerous cross-references to other articles in the Handbook. These may occur either in the body of the article in the form The Title of the Article in Small Caps, or at the end of the article, designated as “Related Reading.” In addition to suggestions for related reading, the reader will find, just prior to the list of references in each article, a mention of the road map(s) in which the article is discussed, as well as background material, when the article is more advanced.

In summary, turn directly to Part III when you need information on a specific topic. Read sections of Part I to gain a general perspective on the basic concepts of brain theory and neural networks. For an overview of some theme, read the Meta-Map in Part II to choose road maps in Part II; read a road map to choose articles in Part III. A road map can also be used as an explicit guide for systematic study of the area under review. Then continue your exploration through further use of road maps, by following cross-references in Part III, by looking up terms of interest in the index, or simply by letting serendipity take its course as you browse through Part III at random.