Sleep and Dreams

I. Facts about Sleep  One-Third of our adult lives are spent in sleep  Experts recommend 8 hours of sleep a night –A typical adult in the U.S. gets a little less than 7 hours a night

II. Biological and Circadian Rhythms  Circadian Rhythm: a cycle that is connected with the 24 hour period of the earth’s rotation –Without cues from the environment, the cycle increases to 25 hours, and we sleep about 10 of those hours.

III. Stages of Sleep  Instruments used in the study of sleep include: –Electroencephalograph (EEG) which measures electrical activity of the brain  Brain waves –Frequencies: # of waves per minute –Amplitude: height of wave; an index of strength  High frequency associated with being awake –Alpha waves: 8-13 cycles per second –Theta waves: 6-8 cycles per second –Delta waves: 1-3 cycles per second

III. Stages of Sleep  Five stages of sleep –When we begin to relax our brain emits alpha waves; low amplitude, cycles per second –1 st four stages of sleep are considered non-rapid-eye- movement (NREM). The 5 th is REM –Stage 1: Brain waves slow down from alpha waves and enter a pattern of 6-8 cycles/second called theta waves  Hypnagogic state: we may experience brief dreamlike images that resemble photographs.  Stage 1 lasts about minutes

III. Stages of Sleep  Stage 2: Brain waves slow to 4-7 cycles/second. There are also sleep spindles3 –Sleep spindles: brief bursts of rapid brain activity; 12 – 16 cycles/second  Stage 3 & 4: Brain waves slow to 1 – 3 cycles/second called delta waves in stage 3 and even more in stage 4 to 0.5 – 2 cycles/second –Difficult to awake a person in stage 4 sleep and lasts about ½ an hour –Sleep walking and sleep terrors typically occur during stage 3 & 4.

III. Stages of Sleep  Then we begin a journey (quick) back upward through the stages until we enter REM sleep. Often called paradoxical sleep because: –EEG patterns look like an awake person’s waves –Difficult to awaken a person in REM –If you do wake a person up, 80% of the time they report having been dreaming –Each night we tend to undergo five trips through the stages of sleep

IV. Functions of Sleep  We do not have all of the answers as to why we sleep  There seems to be some impairment in concentration ability and performance. Also, attention, learning and memory deteriorate when deprived of sleep for several nights.  Why do you need the amount of sleep you need? –The amount of sleep we need may be partially determined genetically –Sleep seems to help us recover from stress  Sleep, learning, and memory –REM and deep sleep are both connected with the consolidation of learning and memory –Being REM deprived interferes with memory.