Foreword Barry Jacobs once memorably commented that the problem in understanding the role of serotonin in the brain was that it was implicated in virtually eve- thing but responsible for nothing 1]. Serotonin (5-HT) is defnitely implicated in the regulation of sleep but what does it do? Once seen as a sleep-promoting molecule, Jacob s own work, lucidly described in this volume, radically changed our view. In fact, serotonin neurons are most active during waking; their - tivity diminishes with sleep onset and disappears during rapid eye movement (REM) sleep. Serotonin, therefore, is intimately linked to the sleep-wake cycle, but what is its role, what mechanisms are involved and what are the impli- tions for sleep medicine and psychiatry? Making progress with these diffcult questions requires a translational approach, which is a research paradigm where both laboratory and clinical neuroscience inform and guide each other with the ultimate aim of improving understanding and treatment of medical conditions. This volume is a superb example of translational research, where leading basic and clinical scientists - tegrate molecular, neuropharmacological and systems approaches to illuminate the reciprocal interactions of serotonin neurons and the mechanisms involved in sleep and circadian regulation. Serotonin is an ancient chemical mediator preserved through at least 500 m- lion years of evolution. In invertebrate animals such as mollusks and leeches, 5-HT cells are distributed throughout the nervous system among the various ganglia."

How does brain activity give rise to sleep, dreams, learning, memory, and language? Do drugs like cocaine and heroin tap into the same neurochemical systems that evolved for life's natural rewards? What are the powerful new tools of molecular biology that are revolutionizing neuroscience? This undergraduate textbook explores the relation between brain, mind, and behavior. It clears away the extraneous detail that so often impedes learning, and describes critical concepts step by step, in straightforward language. Rich illustrations and thought-provoking review questions further illuminate the relations between biological, behavioral, and mental phenomena. With writing that is focused and engaging, even the more challenging topics of neurotransmission and neuroplasticity become enjoyable to learn. While this textbook filters out non-critical details, it includes all key information, allowing readers to remain focused and enjoy the feeling of mastery that comes from a grounded understanding of a topic, from its fundamentals to its implications.