Psychology Topic 9: Sleep and dreaming

REM

Rapid eye movement

REM sleep

5th part of the sleep cycle with REM

• Caused by eyes moving a lot behind the eyelids when dreaming occurs

Sleep cycle

process by which people will pass through the 4 sleep stages + REM sleep in succession several times during a full sleep.

4 stages of sleep

1. Sleep onset

2. Late night stage

3. Deep sleep

4. Deep sleep

(3&4 can be merged)

What is sleep in stages 1-4 called?

NREM sleep

NREM sleep

Non-rapid eye movement sleep

Stage 1- sleep onset

• Light sleep (can easily be woken up)

• Muscles = less active

• Slow eye movements

• You can twitch suddenly (muscle jerk)

• Alpha + theta brain waves

• Alpha brain activity = restful (idling)

• Theta waves show a period between wake and sleep

Stage 2- late night stage

Stage between moving from light sleep to sleep

• Brainwaves slower (mainly theta waves)

• Eye movements stop

• Bursts of brain activity (spindles)

• Body temp starts to drop

• Heart rate slows

Stage 3- deep sleep

• Stage between light + deep sleep

• Slow delta brainwaves

• + faster waves

• Deep sleep- hard to wake up

• Body repairs itself

• Heart + breathing rate continue to fall

Stage 4- deep sleep

• Almost all waves = slow delta waves

• Deep sleep- hard to wake up (cataplesy)

• No eye movements

• When woken up, can feel disorientated

In stage 4 what can children experience when in deep sleep?

• Sleepwalking

• Night terrors

Sleep

Condition of body + mind

• Typically recurs for several hours every night

• Nervous system is inactive, eyes closed, postural muscles relaxed, + consciousness suspended

How can you tell someone is is in REM sleep?

• Eyelids flickering quickly

• Rapid eye movements

When does dreaming occur?

REM sleep

Each night, approx how long do we spend dreaming?

2 hours

What happens during REM sleep?

• Sensory blockade

• Movement inhibition

• Dreaming

Sensory blockade

In REM sleep, all incoming sensory information is stopped

• Sight, sound, touch, taste, smell

How does REM sleep start?

1. Signals in the pons (at base of the brain)

2. Shuts off neurons in the spinal cord, preventing movement

Neuron

A nerve cell that transmits information

Movement inhibition

In REM sleep, when movement is prevented

Characteristics of REM sleep

1. Rapid, shallow, irregular breathing

2. Eyes jerking

3. Muscles paralysed

4. Heart rate + blood pressure rise

5. Dreaming

How many stages of the sleep cycle are there?

4 stages + REM sleep

About how many sleep cycles does a person go through per night?

5 cycles of stages + REM sleep

Approx how long does a cycle of sleep last?

Up to 90 mins

Trends as the sleep cycle progresses through the night

1. 1st cycle- short REM period, more deep sleep (s3+4)

2. Cycles progress → REM sleep lasts longer (1hr), less deep sleep

3. → In the morning we are in mostly S1, S2 + REM sleep

How much sleep do adults and teenagers need per night?

• Adults- 7/8 hrs

• Teenagers- 9 hrs

Sleep deprivation

Not having enough sleep

• Affects physical functioning like weight + brain functioning

Reasons why people over 65 find deep sleep stops

• Age

• Medication

How do animal studies show sleep is needed for survival?

Rats die after 3 weeks if deprived of all sleep

What does having too little sleep increase the risk of?

1. Memory + attention problems

2. Weakened immune system

3. Motor vehicle accidents

4. Increase in BMI (increased risk of obesity due to increased appetite)

5. Depression + substance abuse

Why is REM sleep important?

1. Stimulates learning → increases proteins

2. Benefits learning → stimulates cerebral cortex brain regions (asc with learning) → aids development of brain, esp during infancy

What does sleep help?

1. Brain chemistry restored → neurons repair themselves

2. Deep sleep → avoid breakdown of proteins

What % of sleep is REM sleep for adults vs infants?

• Adults- 20%

• Infants- 50%

What did Dement and Kleitman (1957) find?

1. People report dreams when woken during REM

   • So dreaming takes place during REM

2. But others:

   • Reported dreams when woken during NREM

   • Or didn’t report dreaming when woken from REM sleep

Why do infants have more REM sleep than adults?

• REM sleep stimulates learning → aids development of brain, esp during infancy

• So infants have more REM sleep than adults

Bodily rhythms

Biological, internal rhythms that can happen daily, monthly or annually

Circadian rhythms

Human body rhythms that have a daily (24 hr) cycle

• Sleep-wake cycle, body temperature, some hormonal changes

Sleep-wake cycle

Circadian/daily rhythm, usually triggered by the day-night cycle

• Period of being asleep + awake for 24 hrs

What controls circadian rhythms + where are these found?

Suprachiasmatic nuclei, SCN

• Middle of the brain

What are SCN set by?

External triggers

• Sunlight, other clues to time

Sleep cycle vs sleep-wake cycle

Sleep cycle:

1. Cycles of approx 90 minutes

2. 5 cycles over a night's sleep

3. Ultradian rhythm → lasts for less than 24 hrs

4. Involves S1- 4

5. → move someone from very light sleep to deep sleep, + REM sleep (dreaming occurs)

Sleep-wake cycle

1. Circadian rhythm → lasts approx 24 hrs

2. We are awake for part of it and sleep for part of the 24 hours

3. Within the sleep part is the sleep cycle

What affects the sleep-wake cycle?

1. Jet lag

2. Shift work

How does jet lag affect the sleep-wake cycle when we cross time zones?

1. SWC triggered by light + time cues

2. Different time zones → cues are different

   • Light outside at the time when we would be ‘set‘ to sleep

What can a change in the sleep-wake cycle cause, eg due to jet lag?

• Daytime irritability

• Poor concentration

So SWC important for normal functioning

How does shift work affect the sleep-wake cycle?

1. People doing SW → change what they do at different times in the day

   • Eg work in the dark

2. Cues to time + light are different → affects biological rhythms incl SWC

Ultradian rhythms

Rhythms that occur in a period of less than 24 hours

• Sleep cycle (5 cycles of 90 min periods), heart rate, blood circulation, appetite

How can the ultradian rhythms (eg sleep cycle) affect circadian rhythms (sleep-wake cycle)?

Thinking it is time to wake up when we are hungry

What are the suprachiasmatic nuclei affected by?

Internal + external influences

Internal biological clock

• Endogeneous

• Keeps biological rhythms synchronised

Endogeneous

Internal pacemakers, our biological clock

Hormones

Chemical messengers taking messages through the bloodstream

What does sleep help in relation to hormones?

Reset hormones

• What we do in the day affects our hormone levels

Role of adrenaline + how it affects sleep?

• Fight or flight response to danger, makes us feel alert

• → Makes it hard to fall asleep

When does adrenocorticotropic hormone (ACTH) in pituitary gland release cortisol?

When under stress

Where is adrenocorticotropic hormone (ACTH) found?

Pituitary gland

Role of adrenocorticotropic hormone (ACTH) + how it affects sleep?

• Releases cortisol when under stress

• Causes alertness

• So hard to sleep

• Interferes with SCN trying to make its circadian rhythm

What have studies found about the levels of adrenocorticotropic hormone (ACTH) in people with sleep disorders?

More ACTH in people with insomnia than in people who sleep well

Melatonin

Hormone involved in setting circadian rhythms

• Signals need for sleep

• Sleep-wake cycle + blood pressure

Where is melatonin produced?

Pineal gland

Pineal gland

Small endocrine gland that produces melatonin

Endocrine gland

Produces a hormone that is secreted into the bloodstream

What is melatonin triggered by?

Darkness

Role of melatonin

Helps to synchronise your circadian rhythm

Uses of melatonin

Medication to help with insomnia + jet lag

What does the pineal gland do?

Regulates sleep-wake patterns

• Affects stress levels + physical performance

External influences on sleep

• Environmental features: light + time cues

• Environmental stress

• What we eat + drink

• Medication

What are external cues?

Exogenous

Exogeneous

External cues in the environment that affect our biological clock

Zeitgebers

External cues that synchronise our biological rhytms

• eg to a 24 hr clock

Examples of zeitgebers

• Light-dark cycle

• 12-month cycle of seasons

What can change our experience of zeitgebers?

• Jet lag

• Shift work

→ Affect our mood + performance

Main zeitgeber

Light

How does light interact with out internal body clock?

1. Light enters our eyes

2. Light sensitive cells in the retina of the eye let the internal body clock know if it’s day or night

What can light prevent us from?

Falling asleep

Entrainment

When biological rhythms are matched to their environmental triggers

• Eg circadian rhythms being set in response to external, light, cues

Primary sleep disorder

The disorder is the problem

• Eg insomnia

Secondary sleep disorder

Problems with sleep are symptoms of another disorder

• Eg depression

Insomnia

Problems with sleeping at night that cause difficulties during the day

Narcolepsy

Inability to control sleeping and waking, so experiencing involuntary day time sleeping

Excessive day time sleepiness

Someone with narcolepsy feels extreme sleepiness + can fall into uncontrollable daytime sleep at any time

• Symptom of narcolepsy

Hallucinations

Seeing, hearing, smelling, tasting or feeling something that isn’t there

• Eg monsters, feeling of danger

Cataplexy

Loss of muscle power + tone, triggered by an onset of strong emotions eg laughter

Sleep paralysis

Prevention of movement in REM sleep

• Occurs only when sleeping

Hypocretin (orexin)

Brain chemical that:

• Keeps us awake

• Regulates sleep-wake cycle

Where is hypocretin produced?

Hypothalamus

Unconscious mind

An inaccessible part of the mind that affects behaviour + feelings

Id

Demanding, “I want…”

• Part of Freud’s PT

• Represented as I want in a child’s thinking

Superego

Conscience, “You can’t have…”

Ego

Reasoning, balances demands of id + superego

Manifest content

The story the dreamer tells of what happens in a dream

• Is the dream content (things you see in the dream)

Latent content

Deeper meaning behind what it is said the dream if about

• Hidden behind manifest content

Dreamwork

The transformation of unconscious thoughts into dream content