Sleep deprivation is a sufficient lack of restorative sleep over a cumulative period so as to cause physical or psychiatric symptoms and affect routine performances or tasks. Sleep deprivation and sleep disorders are quite common and affect millions of people world-wide. This book discusses the physiological effects of sleep deprivation on the brain. Cognitive performance efficiency during a night without sleep is also assessed. Current theories concerning the role of sleep in memory processing, such as the Synaptic Homeostasis Theory, are examined. Furthermore, published data regarding sleep in critically ill patients is discussed to increase the awareness among health care professionals in general and the intensive care unit (ICU) staff in particular. Other chapters in this book address the correlation between excessive yawning and sleep deprivation and the types of oculomotor responses that occur in patients who are suffering from sleep deprivation. This new book gathers the latest research from around the globe in this field.