Chapter 7 - Sleep and Dreaming

Abstract

Sleep brings about the most dramatic change in consciousness we are all familiar with. Consciousness nearly fades during deep sleep early in the night, and returns later on in the form of dreams despite our virtual disconnection from the outside world. Meanwhile, the brain goes through an orderly progression of changes in neural activity, epitomized by the occurrence of slow oscillations and spindles. There are also local changes in the activation of many brain regions, as indicated by imaging studies. This chapter considers sleep stages and cycles, brain centers regulating wakefulness and sleep, the neural correlates of wakefulness and sleep including changes in spontaneous neural activity and in metabolism, as well as changes in responsiveness to stimuli. Next, it reviews changes in the level of consciousness during sleep, and considers recent findings concerning the underlying mechanisms. Finally, this chapter examines how consciousness changes during dreaming and discusses the underlying neuropsychology, possible neurocognitive models, as well as the development of dreams. This overview ends with a consideration of dissociated states such as daydreaming, lucid dreaming, sleepwalking, rapid eye movement sleep behavioral disorders, and narcolepsy.