SLEEPDr. Reem Al-Sabah Psychology 220Faculty of medicine
Sleep and Wakefulness What are the similarities between sleep andwakefulness? We think while awake and during sleep (dreaming indicates that we think when we sleep). We form memories while awake and while we sleep (the fact that we can remember our dreams).
People who are asleep may be sensitive to their environment (e.g., parents awakened by their baby’s cry; some people walk in their sleep). Abe to plan ahead (deciding to and actually waking up at a particular time).
The Basics of Sleep Sleep is universal and essential for survival. Three basic characteristics of sleep: 1. Sleep is a brain process 2. It is a active process 3. It is not a single process
Measuring Brain activity Because sleep is a brain process it is commonly studied by recording brain electrical activity. Electroencephalogram (EEG) is the graphic recording of the electrical changes (or brain waves) produced by the electrodes placed on the scalp.
Electroencephalography (EEG) activity is characterized by both frequency and amplitude of the brain waves. Frequency: how many times the waves appear per second [cycles per second (cps); or hertz (Hz)] Amplitude: how high the waveform is on the paper tracing [measures in microvolts (μV)]
EEG Activity Generally divided into four categories according to ranges of frequency from slowest to fastest: 1. Delta waves: 0.5-3 Hz (cycles per second) 2. Theta waves: 4-7 Hz 3. Alpha waves: 8-13 Hz 4. Beta waves: 14-25 Hz Analysis of the pattern of brain waves suggests there are 5 stages of sleep.
Stages of Sleep Stage 1 Stage 2 Stage 3 [NRM sleep] Stage 4 REM (Rapid Eye Movement)
Description of the Stages of SleepWhen awake, most people exhibit brain wave, EEGpatterns that can be classified into: Beta waves (14-25 hertz) Awake stage (day to day wakefulness) highest in frequency and lowest in amplitude, and also more desynchronous than other waves (not very consistent in their pattern) Alpha waves (8-13 hertz) During periods of relaxation, while still awake, our brain waves become slower, increase in amplitude and become more synchronous.
Stage 1 sleep Light sleep, lasts about 5 minutes. Body temperature begins to drop, muscles become relaxed, eyes move slowly from side to side, but easily jarred into wakefulness. Brain waves less regular, reduced amplitude theta waves (4-7 Hz): which are even slower in frequency and greater in amplitude than alpha waves. The difference between relaxation and stage 1 sleep is gradual and subtle. Low amplitude = increased cerebral activation
Stage 2 sleep First stage of established sleep. Lasts 10-20 minutes (first time it occurs). Eyes still, heart rate and breathing slower than when awake, irregular brain activity. Overall, about ½ the night is spent in stage 2 sleep.
theta wave activity continues interspersed with two unusual wave phenomena which occur approximately every minute. Sleep spindles: a sudden increase in wave frequency K-complexes: a sudden increase in wave amplitude. Stages 1 and 2 are relatively "light" stages of sleep. Person will often report not being asleep at all.
Stage 3 and 4 sleep Slow waves, 1-2 Hz- Delta waves. Delta waves are the slowest and highest amplitude brain waves. There is no real division between stages 3 and 4. Stage 3 is considered delta sleep in which less than 50% of the waves are delta waves. stage 4 more than 50% the waves are delta waves.
Delta sleep is our deepest sleep, the point when our brain waves are least like waking. It is most difficult stage in which to wake sleepers, and when they are awakened they are usually sleepy and disoriented. Delta sleep is when sleep walking and sleep talking is most likely to occur. Deeper stages of sleep (3 and 4) occur at the beginning of the night.
REM Sleep (Rapid Eye Movement) Characterized by a sudden and dramatic loss of muscle tone (the skeletal muscles of a person during REM sleep are effectively paralyzed). A sleepers brain waves demonstrate characteristics that are similar to waking sleep, a combination of alpha, beta, and desynchronous waves. This is the stage of sleep most associated with dreaming. REM becomes more prominent in the second half of the night. Usually four or five REM periods in an 8-hour night.
REM Sleep (Cont.) In REM sleep, sensory stimuli do not reach the brain and there are no motor outputs. Areas of the brain involved in the processing of emotional memories show increased activation. 80% of people who wake up during REM sleep will report having a dream (visually vivid with emotional and illogical features, like what we typically associate with “dreams”).
If you wake up during NREM sleep you will remember your dream(s) about 50% of the time (dreams not as vivid as in REM sleep, they are more directly related to events in your life). The longer the period of REM sleep, the more elaborate the reported dream.
Sleep and AgeChildhood Newborns typically spend 70% of each day asleep. Newborns spend more time in REM sleep than children and adults. The percentage of REM sleep declines until adolescence and then stabilizes at adult levels. A circadian pattern of wake and sleep at 1-2 months (rhythmic melatonin secretion identifies at 12 weeks). Sleep continues to be polyphasic with decreasing amounts of daytime napping until age 4 or 5 years.
From ages 5-10 years, children are usually good sleepers with few arousals. Total sleep time usually decreases throughout childhood. However, amount and quality of sleep drops sharply with puberty (due to hormonal and psychosocial reasons)
Old Age Sleep becomes lighter with more and longer nighttime awakenings. Near disappearance of deep or slow wave sleep. REM sleep drops to 18% or less in old age.
NREM Sleep REM SleepQuiet sleep Dreaming sleepAlmost no eye Very rapid eye movementsmovementsDecrease heart and Increased heart ratebreathing ratesMuscles relaxed Almost paralyzed (except for heart, diaphragm, eye muscles, smooth muscles)Decrease in brain’s Increase in brain’s metabolicmetabolic rate(approx. rate30%)Inactive brain in a very Awake brain in a paralyzedrelaxed body body
How is Sleep Regulated?1. Autonomic Nervous System Balance Sleep is associated with an overall change in ANS balance toward parasympathetic dominance. Increases in sympathetic activity may disturb sleep Endogenous causes (fear, anxiety, worry, muscle tension , pain) Exogenous causes (stimulant drugs, excessive heat, sudden/intrusive noise)
Two important characteristics of ANS activity relative to sleep disruption:1. Classical conditioning of autonomically mediated responses. (e.g., if the bed is repeatedly associated with frustrating and unsuccessful attempts to sleep, insomnia may become conditioned).2. The long refractory period following sympathetic nervous system activation. (e.g., once sympathetic arousal has occurred, it may take a while before the sleep-promoting autonomic balance returns).
2. Homeostatic Drive for Sleep Prolonged sleepiness produces sleep debt. The longer individuals remain awake, the sleepier they become. Homeostatic mechanisms help regulate both sleep in general and the specific stages of sleep. When one is deprived of REM sleep, an “REM debt” accrues. When a person then sleeps REM sleep rebounds above normal levels. (similar findings found in SWS deprivation). Thus, there are specialized functional brain requirements for different types of sleep.
3. Circadian Rhythm The clock-dependent alerting process: the process in the brain that arouses us at a particular time each day. Controlled by the ‘biological clock’ in the center of the brain. This clock controls the circadian rhythms, which are rhythms of the body (psychological and physiological changes, as well as rhythms of alertness) that occur approximately every 24 hours. The biological clock is affected by exposure to light: Daylight signals it to stop production of melatonin (a hormone that induces sleep)
Sleep TheoryWhy are we awake and asleep at different times? Opponent-process model of sleep and wakefulness (Edgar & Dement, 1992): The brain possesses two opponent processes that govern the tendency to fall asleep or remain awake.
These two opponent processes interact to produce our daily cycle of sleep and wakefulness. The relative strength of these two processes determines whether we are awake or asleep. During the day, process #3 usually stronger than process #2. Late at night, the biological clock becomes inactive and we fall asleep.
Sleep Disorders About 90% of adults sleep between 6-9 hours per night. Most adults require 71/2 - 8 hours of sleep to not feel sleepy during the day. Sleep disorders are often associated with medical conditions, substance use, environmental factors, emotional disorders, or stressful life events. Sleep Disorder: occurs when the inability to sleep well produces impaired daytime functioning or excessive sleepiness.
Deprivation Most people occasionally deprive themselves of adequate sleep. Fatigue and sleep deprivation can be the cause of many types of accidents. Loss of as little as an hour of sleep increases likelihood of inattentiveness, mistakes, illness, and accidents.
Common sign of sleep deprivation: the inability to get through the day without a temporary loss in energy and alertness, usually occurring in mid-afternoon . (this is not due to eating a heavy meal, sitting in a warm room, or listening to a boring lecture)
Insomnia A complaint of poor quality, insufficient, or nonrestorative sleep. Difficulty falling asleep, Difficulty getting back to sleep during the night Inability to return to sleep Although a real condition, it can be a subjective matter. People seem to overestimate the amount of sleep lost.
Narcolepsy Relatively rare sleep disorders. Narcolepsy chronic neurological disorder caused by the brains inability to regulate sleep-wake cycles normally. Recurring irresistible attacks of drowsiness with the likelihood of falling asleep anytime. Episodes may occur anytime several times a day lasting from a few seconds to 30 minutes. It is the intrusion of REM episodes into the waking hours. Runs in families.
Sleepiness is associated with 3 other symptoms (the narcolepsy tetrad) 1. Cataplexy: a sudden decrease in muscle tone when awake, often triggered by strong emotion or surprise. 2. Hypnagogic or Hypnopompic hallucinations: vivid visual images or sounds that occur as the person is either falling asleep or waking up from sleep 3. Sleep paralysis: as a sleeper is awakening and normal inhibition of muscle tone during REM sleep fails to end when the sleeper becomes awake. All three represent a failure of the neural mechanisms that keep the REM sleep state separate from the waking state.
Apnea the individual stops breathing while asleep May be due to: Failure of the brain to send “breathe” signals to the diaphragm and other breathing muscles, thus stopping breathing. Muscles at top of throat become too relaxed, allowing the windpipe to partially close, forcing breathing muscles to pull harder on incoming air, causing the airway to completely collapse.
Sleep-Wake Schedule Disorders Jet Lag: results from rapid changes in time zone due to transmeridian travel. Symptoms: insomnia, fatigue, gastrointestinal complaints. Which is easier to adjust to: west-bound or east- bound travel? Shift Work: an acute change in work schedule. Symptoms: insomnia, mood changes, GI complaints.
Delayed Sleep Phase Syndrome: is the inability to both fall asleep and wake up at desired times consistent with societal norms. Suffer from sleep-onset insomnia. Symptoms: grogginess in the morning, irritability. Best functioning is in the early evening. Advanced Sleep Phase Syndrome: is the inability to stay awake in the evening and stay asleep in the early morning. Suffer from sleep-maintenance insomnia. May become sleep deprived from postponing their bedtime while still being unable to sleep later in the morning.
Sleep Hygiene www.sleepasssociation.org Maintain a regular sleep routine Avoid naps if possible Don’t stay in bed awake for more than 5-10 minutes. Don’t watch TV or read in bed. Do not drink caffeine inappropriately Avoid inappropriate substances that interfere with sleep Exercise regularly Have a quiet, comfortable bedroom Have a comfortable pre-bedtime routine (a warm bath, shower, Meditation, or quiet time).