Chapter 5 Flashcards
Identify the different stages of sleep and the neural activity in each
Awake: Alpha + **beta
Non-REM sleep:
- Stage 1: Theta
- Stage 2: Spindle + K complex
- Stage 3 and 4 (slow wave sleep): Delta waves
REM sleep:
- high frequency, low amplitude waves that resemble wakefulness
Circadian rhythm
- cyclical changes that occur on a roughly 24-hour basis in any biological processes
- a 24 hour cycle scheduled by environmental cues
Biological clock
term for the suprachiasmatic nucleus (SCN) in the hypothalamus that’s responsible for controlling our levels of alertness
How do our bodies react to a disruption in our biological clocks?
- sleep disruption
- increased risk of injuries
REM sleep
- REM: darting of eyes underneath closed eyelids during sleep
- REM sleep: stage of sleep during which the brain is most active and vivid dreaming most often occurs
- increased heart rate and blood pressure
- rapid, irregular breathing
- dreams more frequent; tend to be emotional, illogical and prone to sudden shifts in plot
- loss of muscle tone
- activity increases to waking levels in many brain structures
- some muscle activity
- some degree of clitoral or penile erection
- spend more time in REM prior to waking up
non-REM (NREM) sleep
stages 1 through 4 of the sleep cycle, during which rapid eye movements do not occur and dreaming is less frequent and vivid
hypnagogic imagery
- scrambled, bizzare and dream-like images that flit in and out of consciousness
- occurs in stage 1 sleep
myoclonic jerks
- sudden jerks of our limbs as if being startled or falling
- occurs in stage 1 sleep
Free running rhythm
- when not exposed to any environmental cues (ie. always dark/light)
- still approximately a 24 hours cycle
List three theories for REM
(1) Those that say REM sleep is important for one’s mental health.
(2) Those that say REM sleep is necessary for the processing of memories.
These theories share one problem: Explaining why tricyclic antidepressant drugs are not debilitating
**(3) Default Theory
Default theory of REM
- REM is a break between bouts of NREM sleep.
- REM maintains a certain level of alertness that would not be possible in continuous NREM (REM keeps you alert to external stimuli).
- REM prepares us for wakefulness (hence the prominence of REM towards the end of a night’s sleep).
REM-sleep deprivation
- A greater tendency for the person to initiate REM (they have to be woken more and more frequently).
- Greater than normal amounts of REM sleep during subsequent nights of sleep. (REM rebound)
Dream theories
- Activation-Synthesis Hypothesis (Hobson, 1989)
- It is our brain trying to make sense of it’s own sleep-related (random) activity - It is a virtual trainer
- The act of dreaming has a major role in early
development (stimulation and simulation) and throughout life (simulation for prediction) - Dreams result from the sleeper’s mind attempting to organize unconsciously reactivated memories. It organizes those reactivations into a narrative (Foulkes, 1982).
- Neurocognitive theory
- dreams are a meaningful product of our cognitive capacities, which shape what we dream about
- Scientists agree that acetylcholine turns on REM sleep and that the forebrain plays an important role in dreams
Lucid dreams
Somewhat akin to being “awake” in a dream: The dreamer is aware that they are dreaming and they can affect the course of the dream.
Support for their existence has come from studies of sleeping subjects who used a prearranged signal to communicate with the experimenter from their dreams.
Common beliefs about dreaming
- Many people believe external stimuli can become incorporated into their dreams.
+ Spraying water on sleeping subjects caused about half of the subjects to incorporate the water into their dreams.
- However, most stimuli are neither incorporated into dream content nor elicit a behavioural response. - Most people believe sleeptalking and sleepwalking (somnambulism) occur during dreams.
- apparently false– paralyzed during REM sleep (although dreams can occur outside of REM sleep)
Why do we sleep?
- Recuperation theories of sleep
- Being awake disrupts homeostasis
- Sleep restores homeostasis
- E.g. Energy levels - Adaptation theories of sleep
- May be no functional purpose
- sleep is the result of a 24 hour timing mechanism
- Protection from accidents & predation
Recuperation vs adaptation theory of sleep
Comparative studies of animals
- more support for recuperation theory
- comparative analysis of sleep
- sleep DOES serve a physiological function
- dolphins sleep with half a brain at a time
- antelopes sleep 2-3 hours a day, even though this puts them at risk for predation
- Sleep is not only for higher order human function
- Doesn’t serve to release emotions to ensure good mental health
- Sleep needed for survival but not in great amounts
- Less during mating, migration, & short supply of food
- No strong relationship between sleep length & body size, energy expenditure, body temperature
Physical, mental, and emotional health impacts of lack of sleep
Physical Health
Impaired immune system.
Hormone dysregulation (inc. appetite).
Mental Health
Cognitive impairment; attention deficits.
Memory lapses or memory loss.
Mental fatigue; hallucinations.
Emotional Health
Irritability; general anxiety.
Inability to handle stress.
Sleep deprivation: Human experiments
Moderate amounts of sleep deprivation–3-4 hours in one night–have been found to have 3 consistent effects:
- Subjects display an increase in sleepiness: They report feeling sleepier and fall asleep quickly if given the chance.
- They display disturbances on written tests of mood.
- They perform poorly on tests of vigilance.
**Microsleeps
What happens during the next sleep after sleep deprivation?
Sleep deprivation leads to increased efficiency to get stage 3&4 sleep, the next sleep
Regain most of stage 4 sleep
More slow wave sleep
Amount of slow wave sleep for 6H = 8H
Naps contain more slow waves if lack of sleep the previous night
Less stage 1&2 when less sleep
Waking during stages 3 & 4 cause sleepiness whereas waking during REM does not
Monophasic sleep
- sleep once, nightly
Polyphasic sleep
- take naps multiple times a day
- Most mammals and human infants regularly sleep more than once per day; they display polyphasic sleep cycles.
Gradual long-term sleep reduction experiment
- In a study by Friedman et al. (1977), subjects reduced nightly sleep by:
- 30 min every 2 weeks until they reached 6.5 h/night;
- Then by 30 min every 3 weeks until they reached 5 h/night;
- Then by 30 min every 4 weeks.
- Once a subject indicated a lack of desire to reduce sleep further, they slept for 1 month at their shortest duration, then for 2 months at the shortest duration plus 30 min; then for a year at whatever duration they wanted.
Gradual long-term sleep reduction results
- Increased sleepiness when less than 6hr/night
- No notable changes in mood, physical health, or performance on tasks of vigilance or memory.
- After 1 year, all subjects had reduced their sleep duration by between 1-2.5 h/night with no excessive sleepiness.
- Subjective responses were often not in line with the objective measures, nor with their performance at work or school.
Stampi nap experiment results
- Subjects required a long time (~2 weeks) to adapt to the schedule.
- Once adapted, they were content and displayed no deficits on performance tests.
- Most displayed a strong preference for particular durations (e.g., 25 min);
- At first, most only showed slow-wave sleep. But eventually all subjects returned to their relative proportions of slow-wave- and REM-sleep–though rarely within the same nap.
How much sleep do we need?
- 7 hours has the lowest mortality rate (correlation!)
- in the gradual long-term sleep reduction experiment, sleeping for at least 6 hours resulted in no notable increased sleepiness or change in mood/physical health/performance on tasks of vigilance or memory.
List 3 types of sleep disorders
- Hypersomnia
- Narcolepsy - Insomnia
- Sleep Apnea
- Periodic limb movement syndrome
- Restless leg syndrome - Sleep walking
Hypersomnia
- disorders of excessive sleep or sleepiness
- ex. Narcolepsy
Symptoms;
1. Severe daytime sleepiness at inappropriate times
2. Cataplexy – loss of muscle tone during wakefulness
3. Sleep paralysis – can’t move as falling asleep or waking up
4. Hypnagogic hallucinations – dreaming while awake
Narcolepsy
- an example of hypersomnia
- experience episodes of sudden sleep lasting anywhere from a few seconds to several minutes (less frequently, as long an hour)
Insomnia
- difficult falling asleep
- ex. Sleep apnea, periodic limb movement syndrome, restless leg syndrome
Symptoms:
1. Having trouble falling asleep (>30 minutes to doze off)
2. Waking too early in the morning
3. Waking during the night and having trouble returning to sleep - higher rates in people who suffer from depression/continual pain/stress
Sleep apnea
- blockage of the airway during sleep
- snore loudly, gasp, sometimes stop breathing for more than 20 seconds
- rouses the person (several hundred times) during the night and interferes with sleep
- no awareness of the awakenings
- associated with being overweight
- wear a facemask attached to a machine that blows air into the nasal passages
Night terrors
- sudden waking episodes characterized by screaming, perspiring, and confusion followed by a return to deep sleep
- occur almost exclusively in children
Sleepwalking
- walking while fully asleep
- not acting out their dreams
- almost always occurs in non-REM (especially stage 3 or 4) sleep
