Book excerpt: This volume describes how the conceptual and technical sophistication of contemporary cognitive and neuroscientific fields has enhanced the neurocognitive understanding of dreaming sleep. Because it is the only naturally-occurring state in which the active brain produces elaborate cognitive processes in the absence of sensory input, the study of dreaming offers a unique cognitive and neurophysiological view of the production of higher cognitive processes. The theory and research included is driven by the search for the most direct relationships linking the neurophysiological characteristics of sleepers to their concurrent cognitive experiences. The search is organized around three sets of theoretical models and the three classes of neurocognitive relationships upon which they are based. The contributions to this volume demonstrate that the field has begun to move in new directions opened up by the rapid advances in contemporary cognitive science, neuropsychology, and neurophysiology.