Sleep
Polysomnography Definition
(Many sleep graphs) An intensive study of a person involving simultaneous monitoring and recording of various physiological responses during sleep.
ASC Sleep Definition
A regularly occurring altered state of consciousness that typically occurs spontaneously and is primarily characterised by a loss of conscious awareness.
What does REM involve?
REM sleep is a period of rapid eye movement sleep during which the eyeballs rapidly move beneath the closed eyelids, darting back and forth and up and down in jerky movements.
Partial sleep deprivation: effects
Tiredness, lack of energy, lapses in attention, inability to concentrate for a long period of time, a low level of motivation, loss of interest and enjoyment in previously enjoyed activities, impaired motor skills, irritability and occasional headaches.
Microsleeps -Definition -EEG patterns -Recollection
-A very short period of drowsiness or sleeping that occurs while a person appears to be awake -During a microsleep, the EEG pattern resembles that of the early stages of NREM sleep. -Individuals may have no recollection of what happened during the microsleep. For example, if you had a microsleep in math's class while the teacher was explaining a new formula, on your return to normal waking consciousness you would have a gap in your knowledge of that information.
Affects on normal daytime functioning
-Difficulties concentrating in class -Mentally 'drifting off' or falling asleep in class -Lethargy -Problems with staying motivated to do class work -Mood swings -Difficulties controlling behaviour
Sleep before midnight
This has led to the belief that sleep before midnight is best because it may beneficial and rejuvenating sleep, since people deprived of stage 4 sleep often complain of muscle aches and tension.
Stages of NREM Sleep: Stage 2
- It lasts for about 10 to 20 minutes. -Body movements lessen, breathing becomes more regular, blood pressure and temperature continue to fall and heart rate is slower. -Brief bursts of higher frequency brain wave activity called sleep spindles periodically appear on the EEG recording. A burst of sleep spindles lasts for about 1 second, and their presence is an indicator that the person is truly asleep. EEG patterns also show bursts of low frequency and slightly higher amplitude waves, called K complexes, in response to arousing stimuli.
Stages of NREM Sleep: Stage 4
-In the first sleep cycle someone may spend up to 20 minutes in stage 4. However as the night progresses, less and less time is spent in stages 3 and 4. -Our muscles are completely relaxed and we rarely move. -Delta waves dominate the EEG pattern and are even slower and larger than those in stage 3. -A person in stage 4 is very difficult to wake. It is at this point people are said to be sleeping like a log or out like a light. When they are woken they can take up to 10 minutes to orient themselves, and usually have a poor memory of sleep events. This is sometimes referred to as sleep inertia (or sleep drunkenness) when referring to the post awakening mental lag. -As the night progresses less and less time is spent in stages 3 and 4. In sleep cycles close to the morning there may be no stage 3 or 4 sleep at all.
REM Sleep
-Is a period of rapid eye movement sleep during which the eyeballs rapidly move beneath the closed eyelids, darting back and forth and up and down in jerky movements. -The brain pattern associated with REM is irregular, consisting of low amplitude, relatively high frequency beta waves, like those produced during alert wakefulness. -REM sleep is clearly more like wakefulness than NREM sleep when brain activity is considered. However if muscle tone is considered, then REM sleep can be called deep sleep due to muscle tone being at its lowest point. -The body's internal functioning is more active during REM sleep than NREM sleep. The heart rate is faster and more irregular. Blood pressure rises and breathing is quicker and more irregular. However the sleeper is totally relaxed.
Total sleep deprivation: Physiological effects
-Physiological Effects: Sleepiness, fatigue, hand tremors, drooping eyelids, difficulty focusing the eyes, lack of energy and strength, slurred speech and an increased sensitivity to pain. After a continuous waking period of 5 days and nights the heart and respiratory system tend to be slower and body temperature drops.
Total sleep deprivation: humans
-Prolonged total sleep deprivation has no long lasting effects, either psychologically or physiologically. -In fact most of the observed and self reported experiences of sleep deprivation were temporary and disappeared after the individual slept uninterrupted.
Total sleep deprivation: Psychological effects
-Psychological Effects: Anxiety disorders, depression, hypertension, sleep disorder, hallucinations, delusions and paranoia.
Sleep problems for adolescents
-Requiring a long time to fall asleep -Insufficient night time sleep on weekdays -Difficulty waking up in the mornings
Methods used to study sleep (8)
-Sleep laboratories -Self reports -EEG (brain) -EMG (muscle) -EOG (eye) -Heart rate and body temperature -Video monitoring -Galvanic skin response
Stages of NREM Sleep: Stage 1
-Stage 1 typically lasts for about 5 to 10 minutes, but for as little as 30 seconds for some people or up to 10 minutes for others. -We tend to gradually lose awareness of ourselves and our surroundings, but some of the time we are actually aware if faint sounds in our environment. -Lower level of bodily arousal, decrease in heart rate, respiration, body temperature and muscle tension. -The EEG pattern shows a decrease in alpha wave production as these brain waves are replaced by more irregular medium-frequency theta waves, which have a mixture of high and low amplitude. -As the result of the muscles relaxing, we sometimes experience a 'jerking' sensation whereby our body, or apart of our body, seems to go into a spasm. This stage 1 spasm is known as a hypnic jerk. -If we are woken during Stage 1, we may feel as if we haven't been asleep at all.
How much sleep adolescents are getting & require.
-The amount of sleep adolescent males and females between the ages of 13 and 19 years get is between 8 and 10 hours. -The amount of sleep adolescent males and females between the ages of 13 and 19 years require is more than 9 hours.
Changes to adolescents sleep-wake patterns
-They sleep for less hours per night (even though their requirement is roughly the same) -They go to bed later than when they were a child -They rise later in the day -They are more sleepy during the day than children -They sleep in more on weekends (to compensate for their lack of sleep received during the week)
Stages of NREM Sleep: Stage 3
-This period lasts for about 10 minutes. -Heart rate, blood pressure and body temperature continue to drop and the breathing rate continues to be slow and steady. -There is a reduction in the brains electrical activity, and delta waves begin to appear in the EEG recording. Delta waves make up about 20-50% of the brain waves recorded during stage 3, being slow, large, regular brain waves. They are lower in frequency and higher in amplitude than the alpha and theta waves of stages 1 and 2. -The individual is extremely relaxed and becomes less and less responsive to the outside world. In this stage people are difficult to arouse, but if they are awoken they are often groggy and disoriented.
Sleep spindle
A brief burst of higher frequency brain wave activity during NREM stage 2 sleep. Usually last for about 1 second. It indicates if the person is truly asleep.
K complex
A burst of low frequency and slightly higher amplitude waves in response to arousing stimuli during NREM stage 2 sleep.
Psychological and social factors that lead to pressure towards later sleep times.
Adolescents typically like to exert their growing need for independence which can include making decisions about when to go to bed or sleep. Many usually decide to go to sleep later, as early sleep times are associated with childhood. Essentially sleep is a low priority for many adolescents. This typically results in erratic sleep habits they compound sleep problems and result in sleep deprivation to an extent that impairs function during waking time.
Paradoxical sleep
An observer may say the sleeper appears paralyzed during REM sleep. Consequently, REM sleep is called paradoxical sleep - internally the brain and body are active while externally the body appears calm and inactive. The purpose of the apparent body paralysis is still unknown. However some psychologists have suggested that it may have evolved to prevent us from acting out our dreams, and thereby minimize any potential harm.
Proportions of NREM & REM in a nights sleep
Approximately 80 % of our sleep time is spent in NREM sleep, and typically the first half of the night has more NREM sleep than the second half of the night.
Why is unethical to perform tests on humans?
Because of the potential for psychological and physiological harm.
EMG (muscle)
Detect, amplify and record the electrical activity of muscles. Show the strength of electrical activity occurring in the muscles, which indicates the changes in muscle activity (movement) and muscle tone (tension). It is obtained by attaching electrodes to the skin above the particular muscles whose activity is being monitored. Are displayed as line graphs, similar to those produced by the EEG. They can be produced on paper or on a computer monitor.
Dreams
Dreaming also occurs in NREM sleep, but the dreams are less frequent, less memorable, less vivid and less fragmented than those of REM dreams. A REM period that occurs early in the night may last for only a few minutes, while a later REM period may last up to an hour or so. This may explain why you are often dreaming when you are woken by an alarm in the morning.
Sleep laboratories
Has one or more small bedrooms furnished and decorated to be as homelike and comfortable as possible (but also soundproof).The person is connected to an adjoining control room where researchers monitor sleep patterns throughout the night. Precise observations and measurements can be made during sleep without actually waking the person. Electrical activity of the brain, information about eye movements and the bodies muscle tone or tension, heart rate, body temperature, breathing rate, body position, leg movements and snoring.
Amount of sleep adolescents need for optimal brain functioning.
His (Michael Gradisar (2009)) research found that adolescents should sleep for around 8 or 9 hours per night for optimal brain functioning, anything less disadvantages short term memory and other mental processes.
Criticism of Restorative Theory
If restoration is the only function of sleep, we would expect that a physically disabled person confined to bed would sleep less than a physically active person. This however is not the case.
Function of NREM sleep
NREM sleep may be the time when the body recovers, repairing body tissue, removing waste products and replenishing neurotransmitters that are vital to communication between neurons.
Theories of why we sleep (2)
Restorative (restore and repair) Survival (adaptive and evolutionary)
EEG (brain)
That as we fall asleep, and throughout a typical sleep period, the brain produces distinguishable patterns of electrical activity that tend to follow a regular sequence.
Sleep deprivation definition
Going without sleep
Heart rate and body temperature
Gradually drop as we progressively drift from light sleep into deeper and deeper sleep, then gradually increase as we drift from deeper sleep to lighter sleep.
REM Rebound
Involves catching up on REM sleep immediately following a period of lost REM sleep by spending more time than usual in REM sleep when next asleep.
Galvanic skin response
Is a physiological response that indicates the change in the resistance of the skin's surface to the passage of an electrical current. Changes in GSR are closely associated with emotional experiences and can also indicate levels of alertness.
EOG (eye)
Measures eye movements or eye positions by detecting, amplifying and recording, electrical activity in eye muscles that control eye movements. Through electrodes attached to areas of the face surrounding the eyes. Are displayed as line graphs, similar to those produced by the EEG and EMG. They can also be produced on paper or on a computer monitor.
Two states of sleep
NREM (Non-rapid eye movement) REM (Rapid eye movement)
Types of sleep deprivation and what they entail
Partial sleep deprivation involves having less than what is normally required. Total sleep deprivation involves not having any sleep at all.
Biologically (physiologically) driven sleep needs and patterns that lead to pressure towards later sleep times.
Primarily involve the body's natural, inbuilt timing system, or 'biological clock'. Each day our body goes through a cycle during which hormones are produced to control body functions. This is called the circadian rhythm/cycle. The sleep hormone melatonin causes us to feel sleepy at night. The cycle is linked to external cues in the environment such as the presence or absence of sunlight, alarm clocks, meal times and even television.
Restorative Theory
Sleep provides an opportunity for the body to replenish the stores of energy that have been depleted during the day. It also allows any damaged cells to be repaired and various muscles to be detoxified or rid themselves of waste products. Generally, NREM sleep is believed to be important for restoring and repairing the body. REM sleep is believed to restore the brain and may have a role in higher mental functions such as leaning and memory. Brain growth and restoration occur during REM sleep.
Partial sleep deprivation: severity of effects
The severity and extent of the side effects depend on the individual, the amount of sleep lost, and the period of time over which the sleep deprivation occurs.
Survival Theory
The survival theories of sleep propose that sleep evolved to enhance survival by protecting an organism through making it inactive during the part of the day when it is most risky or dangerous to move about. According to survival theories, sleep serves the function of protecting the sleeper from harm or death, and therefore enhances the survival of the species.
Sleep problems from adolescence to adulthood.
There is also research evidence that sleep problems that continue into adulthood can lead to the development of anxiety disorders in the late twenties and can also lead to major depression.
Criticism of Survival Theory
They do not explain why sleep involves a loss of awareness, since the loss of consciousness during sleep may place the organism at greater risk. While asleep the organisms senses are less attuned to the environment and muscles are in a relaxed state, not ready to respond to danger.
Older people (lighter sleep & awakenings)
This coincides with polysomnography research findings that NREM sleep of elderly people is mostly stage 2 shallow sleep. By age 90, stage 3 and 4 sleep is rarely experienced, if at all.
Video monitoring
To record externally observable physiological responses throughout the sleep cycle, including behaviors when falling asleep and when waking.
Why is total sleep deprivation hard to achieve?
Total sleep deprivation is difficult to ensure because after 3 or 4 sleepless days, people automatically drift into periods of microsleep over which they have no control.
Total sleep deprivation: rats
Unable to maintain a constant body temperature, resulting in excessive heat loss. They eventually died after 2-3 weeks of no sleep. Autopsies conducted after their death showed that their immune systems had collapsed, resulting in blood poisoning and ultimately death.
Self reports
Valuable in providing information about mental processes such as thoughts and feelings associated with different stages and types of sleep.
Theories of sleep function
We need sleep, unclear exactly why. Amount of sleep needed varies.
Amount of time spent sleeping in REM sleep and as a percentage
Newborn infant 8hr 50% End of infancy 4hr 30% End of childhood and onset of adolescence 2hr 20% Late adulthood 2hr 33%