Stages of Sleep

 Alpha wave type of relatively low frequency, relatively high amplitude brain wave that becomes synchronized; characteristic of the beginning of stage 1 sleep

Delta wave type of low frequency, high amplitude brain wave characteristic of stage 3 and stage 4 sleep

Collective unconscious theoretical repository of information shared by all people across cultures, as described by Carl Jung

K-complex very high amplitude pattern of brain activity associated with stage 2 sleep that may occur in response to environmental stimuli

Latent content hidden meaning of a dream, per Sigmund Freud’s view of the function of dreams

Lucid dream people become aware that they are dreaming and can control the dream’s content

Manifest content storyline of events that occur during a dream, per Sigmund Freud’s view of the function of dreams

Non-REM (NREM) period of sleep outside periods of rapid eye movement (REM) sleep

rapid eye movement (REM) sleep  period of sleep characterized by brain waves very similar to those during wakefulness and by darting movements of the eyes under closed eyelids

Sleep spindle rapid burst of high frequency brain waves during stage 2 sleep that may be important for learning and memory

Stage 1 sleep first stage of sleep; transitional phase that occurs between wakefulness and sleep; the period during which a person drifts off to sleep

Stage 2 sleep second stage of sleep; the body goes into deep relaxation; characterized by the appearance of sleep spindles

Stage 3 sleep third stage of sleep; deep sleep characterized by low frequency, high amplitude delta waves

Stage 4 sleep fourth stage of sleep; deep sleep characterized by low frequency, high amplitude delta waves

Theta wave type of low frequency, low amplitude brain wave characteristic of the end of stage 1 sleep