SLEEP AND DREAMS

SLEEP AND DREAMS

SleepHow many hours a night do you sleep during the week?On a weekend?At what times throughout the day do you feel most tired?If you didnt have school what time would you go to sleep/ wake up?Do you think most students get enough sleep why/why not?

SLEEPImagine...if on the average, people sleep 8 hours a day, they are sleeping away 1/3 of their life. How much is that? How much we sleep ??Well, 8 hours of sleep every day is the same as 233,600 hours of sleep by the time you are 80 years old. That's the same as sleeping 26.67 years!!!

Why we have to sleep?Revive tired bodyBuild up resistance to infectionRecovery from stress, consolidation of memories

Sleep needsAs people age, they decrease sleep time, in general, although some people begin to sleep more in old age.

Newborns spend approximately 16 hrs. per day sleeping, and 50% of the sleep time in RAPID EYE MOVEMENT (REM).

As children move toward adulthood, less and less time is spent sleeping, and only 20% of the sleep time is in REM.

Changes in Sleep Patterns over the Lifespan

Circadian RhythmsMuch of the bodys activities including the desire to sleep are governed by:

Circadian rhythm = biological clock

Circadian RhythmsHuman and some other animals rely on vision for survival are active during the day and inactive at night.Rates, mice and other less visual animals are active at night and inactive during the day.Each species generates a rhythm of activity an inactivity lasting about one day Circadian RhythmsThe rising and setting of the sun provide a cue to reseat our rhythm each day and keep it at exactly 24 hours in a normal condition.

In an environment with no cues to time most people generate a waking-sleeping rhythm lasting between 24-25 hours (Moore Ede, Czeisler & Richardson, 1983) Suprachiasmatic Nucleus (SCN)SCN: area of the hypothalamus that sets circadian rhythmif damaged, rhythms are less consistent, not synchronized to light and dark patternsneurons produce circadian rhythm in tissue cultures genes interact with proteins per and tim to generate rhythm mutant per gene accelerates biological clockPineal gland releases melatonin 2 hrs before bedtimepill may help adjust to new time zone but effect of long term use unknown

Figure: The suprachiasmatic nucleus (SCN) of rates and humans. The SCN is located at the base of the brain, just above the op[tic chiasm. The optic chiasm was torn off when the brain was sliced to make the slides shown in (a) and (b), which show coronal sections through the plane of the anterior hypothalamus. Each rat was injected with radioactive 2-deoxyglucose, which is absorbed by the most active neurons. A high level of absorption of this chemical produces a dark appearance on the slide. Note that the level of activity in SCN neurons is much higher in section (a), in which the rat was injected during the day, than in section (b), in which the rat received the injection at night. (Source: W.J. Schwartz & Gainer, 1977 A sagittal section through a human brain shows the SCN and the pineal gland.)

Setting and Resetting Biological ClockBiological clock is primarily reset by light, the zeitgeber, or time giver blind people produce circadian rhythms longer than 24 hoursunder constant bright light, hamsters developed two periods of wakefulness and sleep also affected by noise, meals, exercise and temperaturemarine animals affected by tide

Setting and Resetting Biological ClockJET LAG is a physiological condition which results from alterations to the body's circadian rhythms resulting from rapid long-distance trans meridian (eastwest or westeast) travel on aircraft. It was previously classified as one of the circadian rhythm sleep disorders.

The condition of jet lag may last several days until one is fully adjusted to the new time zone, and a recovery rate of one day per time zone crossed is a suggested guideline. The issue of jet lag is especially pronounced for airline pilots, crew, and frequent travelers. Airlines have regulations aimed at combating pilot fatigue caused by jet lag.

The common term jet lag is used because before the arrival of passenger jet aircraft, it was generally uncommon to travel far and fast enough to cause jet lag. Propeller flights were slower and of more limited distance than jet flights, and thus did not contribute as widely to the problem.

World Time Different

Figure: Jet LagJet lag. Eastern time is later than western time. People who travel six time zones east must wake up when their biological clocks say it is the middle of the night, and will try to go to sleep when their biological clocks say it is just late afternoon.

Symptoms of Jet LagDisturbed sleep such as insomnia, early waking or excessive sleepiness Daytime fatigue Difficulty concentrating or functioning at your usual level Stomach problems, constipation or diarrhea A general feeling of not being well Muscle soreness Menstrual symptoms in women

Setting and Resetting Biological ClockShift workmany people may not adjust completely to night work, still feel groggy and do not sleep well during dayless light in night environment

Setting and Resetting Biological ClockSCN reset by axons in retinohypothalamic pathway from retina to hypothalamus retinal ganglion cells do not contribute to vision and respond to overall average amount of lightlight still resets biological clock in mice with few rods and coneslight resets circadian rhythm in blind mole rats

The Sleep and Waking CycleFirst studies by Eugene Aserinsky and Nathaniel Kleitman, 1960

Instruments used in researchElectroencephalograph: brain electrical activityElectromyograph: muscle activity Electrooculograph: eye movementsOther bodily functions also observed22Psychologists who conduct sleep research use the instruments a great deal: the EEG, which records brain electrical activity; the EMG, which records muscle activity and tension; and the EOG, which records eye movements.

They may also record heart rate, breathing rate, temperature, etc., as well as videotape the person sleeping through a window. Believe it or not, most people get used to the wires and cameras after only one night.Cycling Through the Stages of SleepStage 1: brief, transitional (1-7 minutes)alpha -> thetaStage 2: sleep spindles Stages 3 & 4: slow-wave sleep Stage 5: REM, EEG similar to awake, vivid dreaming (initially a few minutes, progressively longer as cycle through the stages)23Sleep researchers have discovered 5 distinctly different stages of sleep, based on physiological recordings.

Stage 1 is a brief, transitional stage of light sleep that lasts between 1 and 7 minutes. The EEG moves from predominately alpha waves when the person is just about to fall asleep, to more theta activity.

Stage 2 is characterized by more mixed brain wave activity with brief bursts of higher-frequency brain waves, called sleep spindlesas a person continues sleeping they move into more slow-wave sleep, exhibiting more theta and delta waves.

Stages 3 and 4 are characterized by low frequency delta waves.

When stage 1 should be next in line in the cycle, something interesting happensrapid eye movement (REM) sleep begins.

REM sleep is characterized by an EEG that looks awake and alertand by rapidly moving eyes behind the lids, an irregular pulse and breathing rate, and loss of muscle tone. When someone is awakened from REM sleep, they report vivid dreaming.

EEG (electroencephalogram) which shows a record of brain activityEMG (electromyogram) shows muscle activityEOG (electroculogram) shows eye movements

25Figure 5.4EEG patterns in sleep and wakefulness.Characteristic brain waves vary depending on ones state of consciousness. Generally, as people move from an awake state through deeper stages of sleep, their brain waves decrease in frequency (cycles per second) and increase in amplitude (height). However, brain waves during REM sleep resemble wide-awake brain waves. (Figure from Current Concepts:The Sleep Disorders, by P. Hauri, 1982, The Upjohn Company, Kalamazoo, Michigan. Reprinted by permission.)

Stages of sleep

An overview of the cycle of sleep27An overview of the cycle of sleep.The white line charts how a typical person moves through the various stages of sleep during the course of a night. This diagram also shows how dreams and rapid eye movements coincide with REM sleep, whereas posture changes occur in between REM periods (because the body is nearly paralyzed during REM sleep). Notice how the person cycles into REM four times, as descents into NREM sleep get shallower and REM periods get longer. Thus, slow-wave sleep is prominent early in the night, while REM and stage 2 sleep dominate the second half of a nights sleep.

The white line charts how a typical person moves through the various stages of sleep during the course of a night. This diagram also shows how dreams and rapid eye movements coincide with REM sleep, whereas posture changes occur in between REM periods (because the body is nearly paralyzed during REM sleep). Notice how the person cycles into REM four times, as descents into NREM sleep get shallower and REM periods get longer. Thus, slow-wave sleep is prominent early in the night, while REM and stage 2 sleep dominate the second half of a nights sleep.Sleep Cycle28REM SleepDreaming occursEyes move back and forth rapidly EEG pattern during REM sleep is similar to the EEG when you are awakeHowever, the EMG is very quiet during REM sleep - one theory is that during REM sleep, the muscles are inactive so that we will not act out our dreams. This also means that sleepwalkers are not in REM sleep and are not acting out their dreams.

Problems in the Night: InsomniaThe most common sleep disorder is insomnia.

Insomnia occurs in 3 different patterns:trouble falling asleeptrouble remaining asleeppersistent early morning awakening.

About 15% of adults have severe or frequent insomnia, and another 15% have mild or occasional.

InsomniaInsomnia can have many different causes, from anxiety and tension to drug use, such as caffeine.The most common approach for treating insomnia is the use of sedatives5-15% of adults use sleep medications with some regularity this is a poor long-term solution.

DreamDreams are conventionally defined as mental experiences during REM sleep that are often based in vivid imagery, have a story like quality, are often seems real to the dreamer. Dreams can be extraordinarily vivid or very vague; filled with joyful emotions or frightening imagery; focused and understandable or unclear and confusing

Why do we dream? Why do we dream? What purpose do dreams serve? While many theories have been proposed, no single consensus has emerged. Considering the enormous amount of time we spend in a dreaming state, the fact that researchers do not yet understand the purpose of dreams may seem baffling.Dream ContentResearch shows that the content of dreams is usually familiar. Common themes in dreams include things like falling, being pursued, trying repeatedly to do something, school, sex, being late, eating, being frightened, etc.

Sigmund Freuds theory of dreams suggested that dreams were a representation of unconscious desires, thoughts and motivations. According to Freuds psychoanalytic view of personality, people are driven by aggressive and sexual instincts that are repressed from conscious awareness.

People in Western cultures pay little attention to dreams as meaningful messages in their lives, while people from many non-Western cultures are likely to view dreams as important information about oneself, the future, or the spiritual world.