This comprehensive text on the fundamental brain sources of human and animal feelings summarizes up-to-date information about the subcortical operating systems that organize the fundamental emotional tendencies of all mammals. Complex material is presented in a comprehensive but readable manner. The book approaches emotions from the perspective of basic emotion theory, but does not fail to address the more complex issues raised by constructionist approaches, including relations to human consciousness. Representing a synthetic integration of vast amounts of neurobehavioral knowledge, this book may be the most important contribution to understanding the biology of emotions since Darwin's Expression of Emotions in Man and Animals. Throughout, the psychiatric implications of this type of knowledge are also addressed.