Starting with a general introduction to brain chemistry, this volume takes the reader on a journey through normal brain processes, into the world of drug-induced changes in consciousness, and finally into the chilling world of dysfunctions in consciousness. In doing so, it does not seek to explain, or even to define, consciousness. Instead, significant information is provided on neurochemical correlates of well recognized states and alterations of consciousness. These include natural functions such as attention, memory, motivation, sleep and dreaming. Changes induced by drugs and by pathological states add further important information based on the premise that mechanisms associated with disrupting or abolishing consciousness will help to identify those underpinning normal conscious awareness.