Sleep Patterns and Theories MODULE 23

Circadian Rhythm 24hr cycle of day & night Body temp increases through the day, dips slightly in the mid afternoon (siesta) and falls in the evening Thinking & memory are most accurate when people are at their peak in circadian arousal. Morning/Night person? With age we tend to shift from being owls to larks

Sleep Sleep is a state of consciousness. We are less aware of our surroundings. Parts of the cortex stop communicating but are still active.

Waking Up and Falling Asleep Morning light tweaks circadian clock  activates light-sensitive retinal proteins Signals brains suprachiasmatic nucleus (SCN) in the hypothalamus Pineal gland Stop producing melatonin in the AM Start producing melatonin in the PM

Sleep Cycle Use an EEG machine to measure stages of sleep. 4 distinct stages When you are in the onset of sleep (getting ready to fall asleep) you experience alpha waves. ONE CYCLE LASTS 90 MINUTES

Non-REM Stage 1 (NREM-1) Kind of awake and kind of asleep. Only lasts a few minutes, and you usually only experience it once a night. May experience hallucinations – sensory experiences without stimulation feeling of falling or floating jerking body movements Feeling pinned

Non-REM Stage 2 (NREM-2) Lasts about 20 min Begin to show sleep spindles…short bursts of rapid brain waves. Clearly asleep but can be easily woken up Sleep talking (nonsensical/garbled) can occur in this stage or later

Non-REM Stage 3 (NREM-3) Slow wave sleep. You produce Delta waves. Hard to awaken… you will be very groggy. Vital for restoring body’s growth hormones and good overall health. Lasts about 30 min. Young children may experience bedwetting/sleepwalking At the end of NREM-3 you ascend back up through NREM-2 to reach REM

REM Sleep Rapid Eye Movement Often called paradoxical sleep because the body is internally aroused & externally calm Brain is very active. Dreams usually occur in REM Emotional, usually story like and richly hallucinatory Body is essentially paralyzed – motor cortex is active but signals are blocked by the brainstem Lasts about 10 minutes Heart rate rises, rapid irregular breathing, eyes dart around, genitals become aroused

REM Sleep During the night, REM and NREM-2 sleep increases and NREM-3 becomes shorter. Sleep cycle repeats itself about every 90 min. By morning, 20-25% of night’s sleep has been spent dreaming (about 100 min = 600 hours/year = 15,000 dreams = 100,000 dreams/lifetime) 37% of people report few/no dreams but under experimental conditions  woken up during REM they will recall some details of a dream

Stages in a Typical Night’s Sleep 1 2 3 4 5 6 7 Sleep stages Awake Hours of sleep REM

How much sleep do we need? Range in humans – 4-10 hours with average of 7.5 hours. Why does it vary? Varies with age & from person to person Newborns 2/3 of the day (16 hrs) Adults 1/3 of the day (8 hrs) Sleep patterns are culturally influenced US: typically 7-8 hrs… much less than our past Modern light bulb, shift work, social diversions/technology Time zones/travel, daylight savings

How much sleep do we need? Stanley Coren study (1996) Found most people will sleep 9+ hrs uninterrupted. Don’t get groggy Awake refreshed, with better moods, perform more efficient & accurate work than those with less sleep.

Sleep Theories Sleep protects us Sleep lets us recuperate Darkness increases danger – species dependent on vision We were safer in a cave/shelter/house Sleep lets us recuperate Restore and repair brain tissue Sleep is when fading memories are restored Consolidates memory People recall performance task training better after sleep … even a short nap

Sleep Theories 4. Sleep feeds creative thinking Dreams are sources of inspiration Enhances problem solving, learning and spotting connections 5. Sleep supports growth Pituitary gland releases a growth hormone  necessary for muscle development Dramatically improves athletic performance Babies sleep 16 hours vs. elderly sleep 6 hours