Preface -- Basics of sleep and wakefulness. Genetic dissection of sleep homeostasis -- Sleep, sleep deprivation and gene expression -- Sleep and synaptic homeostasis -- Sleep and neuronal plasticity -- Sleep and adult neurogenesis: implications for cognition and mood -- Sleep & memory: molecular mechanisms -- Sleep & memory in birds -- MRI studies of sleep and memory in humans -- Sleep & memory: cognitive function in humans -- Sleep and cognition in ageing and dementia -- The adenosine system, caffeine, and performance.- Orexin/Hypocretin regulation of arousal and optogenetics -- Sleep, stress and arousal -- Sleep and emotional regulation -- Sleep and psychiatric disorders (PTSD, anxiety, aggression, schizophrenia) -- Sleep disruption as a causal factor in depression -- Sleep deprivation therapy for depression -- Pharmacology of sleep and sleep disorders. This book reviews current knowledge on the importance of sleep for brain function, from molecular mechanisms to behavioral output, with special emphasis on the question of how sleep and sleep loss ultimately affect cognition and mood. It provides an extensive overview of the latest insights in the role of sleep in regulating gene expression, synaptic plasticity and neurogenesis, and how that in turn is linked to learning and memory processes. In addition, readers will learn about the potential clinical implications of insufficient sleep and discover how chronically restricted or disrupted sleep may contribute to age-related cognitive decline and the development of psychiatric disorders such as schizophrenia and depression. The book consists of 19 chapters, written by experts in basic sleep research and sleep medicine, which together cover a wide range of topics on the importance of sleep and consequences of sleep disruption. This book will be of interest to students, researchers and clinicians with a general interest in brain function or a specific interest in sleep.