For centuries humankind has been fascinated by how the brain and the rest of the nervous system work. Only in the twentieth century did we truly begin to develop the sort of scientific understanding of this topic detailed enough to permit a quantitative treatment of the many questions this study raises. Whatever one's philosophy may be over the question of "mind" vs. "brain" – and there are many diverse opinions on this – the simple fact is that wherever we find "mind" there also we find "brain." This makes the study of brain, spinal cord, and the peripheral nervous system arguably the most human, and in some ways the most personal, of scientific topics. This book is a quantitative introduction to the modeling of biological systems and their signals. Topical coverage is provided from the sub-neuron level to the level of psychological models of brain function. Its chapters on neural network theory span the scope of neuron and neural network modeling from the Hodgkin-Huxley model all the way to Adaptive Resonance Theory models of brain function.