Sleep and Dreaming

Sleep: can be defined as a recurring condition of the body and mind over several hours each night, in which an individual’s consciousness is temporarily suspended.


A periodic, natural, reversible and near total loss of consciousness

Biological rhythms of sleep

These refer to the regular contrasts in a person’s biological activity

Such as:

  • Changes in levels of brain chemicals
  • Regulation of bodily temperatures in a day
  • The shift between sleeping and waking.

Circadian rhythms: A biological rhythm with a cycle lasting for 24 hours.

Ultradian rhythms: A biological rhythm that has more than one cycle in 24 hours.

The four stages of sleep (And the REM sleep)

Stage 1:

  • Light sleep – the person can be woken up easily
  • Muscle activity lessens
  • Slowed eye movements – muscles start to twitch
  • Alpha brain waves – lead to restlessness
  • Theta brain waves – this is the period between sleep and wake

Stage 2:

  • Known as the ‘late night sleep’ stage
  • Brain waves are slower
  • Mainly Theta waves
  • No eye movements
  • ‘Spindles’ of brain activity
  • Body temperature / Heart rate drops 

Stage 3:

  • Known as the ‘Deep sleep’ stage
  • Consists of slow Delta waves, some may be faster
  • Stage between light and deep sleep

Stage 4:

  • The final ‘Deep sleep’ stage
  • Slow delta waves only
  • Harder to wake up in this stage
  • No eye movement
  • Person may feel disorientation
  • Most people experience sleep walking / Night terrors in this stage

REM sleep: Rapid Eye Movement (REM) is a recurring sleep stage during which vivid dreaming commonly occurs.

  • Rapid eye movement – the eyelids can be seen flickering quickly
  • Dreaming occurs during this time
  • 2 hours of sleep is spent on dreaming

During REM sleep, any incoming information from the senses (i.e. touch, sight, sound, smell, taste) is blocked

  • Known as Sensory Blockade

The REM sleep starts with signals in the pons, at the base of the brain, shutting of neurons in the spinal cord and preventing movement.

  • Known as Movement Inhibition

Some more characteristics:

  • Shallow, rapid and irregular breathing
  • Eyes jerking
  • Paralysis of muscles

NREM sleep (Non-Rapid Eye Movement): One of the two distinctive types of sleep that is found in mammals. As deeper sleep is achieved, the waves displayed by the synchronized EEG become larger and slower. And because of this, sleep stages 3 and 4 of NREM can be referred to as the slow-wave sleep (SWS).

Note – Different sources may refer to NREM sleep or to slow-wave sleep, but NREM is a better term to use as the lighter stages of sleep do not have slow waves in the EEG. SWS refers to the proper deep stages of NREM (Stages 3 and 4).

Oneirology: Study of dreams

Recuperation: Allowing our neurons and cells to rest and repair themselves

Sleep deprivation: Not having enough sleep

Sleep debt: Having too little sleep over several days or weeks

This can affect physical functioning such as weight and brain functioning and growth.

A few sleep disorders

Insomnia: trouble in falling or staying asleep

Narcolepsy: uncontrollable sleep attacks

Sleep apnea: Causes the sleeper to temporarily stop breathing

Explaining the difference between a sleep cycle and a sleep-wake cycle

The sleep cycle involves cycles of about 90 minutes and there are about five such cycles over a night’s sleep. The sleep cycle is an ultradian rhythm as it lasts for less than 24 hours. The sleep cycle involves Stages 1 to 4, which move someone from very light sleep to deep sleep, as well as REM sleep, which is where dreaming takes place. The sleep-wake cycle is a circadian rhythm lasting around 24 hours where we are awake for part of it and sleep for part of the 24 hours. Within the sleep part is the sleep cycle which helps to underline the differences between the sleep cycle and the sleep-wake cycle.

The circadian rhythm is controlled by the Hypothalamus

Psych apply it Page 232: Exam-style question.

Internal and External influences on sleep

The suprachiasmatic nuclei (SCN) is affected by both internal and external influences


Our internal biological clock is endogenous ( internal ) and keeps biological rhythms in sync.

  • Circadian rhythms
  • Ultradiun rhythms

These, including hormones such as melatonin and Adrenocorticotropic hormone ( ACTH )

The pineal gland is a small endocrine gland located in the brain. It produces and secretes the hormone melatonin, which is a hormone that helps regulate biological rhythms such as sleep-wake cycles. The secretion of melatonin is inhibited by light and triggered by darkness.

So, in a shortened manner

Melatonin: hormone involved in setting circadian rhythms

Pineal gland: small endocrine gland that produces the hormone melatonin


Light’s Effect

Light exposure can cause the biological clock to either advance or delay, which affects the sleep and wake cycle.

Light is one of the most important external factors that can affect sleep. It does so directly, by making it difficult for people to fall asleep, and indirectly, by influencing the timing of our internal clock and affecting the preferred time to sleep.

Light influences our internal clock through specialized ‘light sensitive’ cells in the retina of the eyes. These cells, which occupy the same space as the rods and cones that make vision possible, tell the brain whether it is day or night, and sleep patterns are set accordingly.

Jet Lag and Shift Work

Normally, light serves to set the internal clock to the appropriate time. However, problems can occur when exposure to light changes due to a shift in work schedule or travel across time zones. Under normal conditions, the internal clock largely influences the ability to sleep at various times over the course of a 24-hour period, as well as which sleep stages an individual experiences when they do sleep.

Long-distance traveler’s experience ‘jet lag’ as their internal clock adjusts to the new daytime-nighttime cycle.

Individuals who travel across time zones or work the night shift typically have two symptoms. One is insomnia when they are trying to sleep outside of their internal phase, and the other is excessive sleepiness during the time when their internal clock says that they should be asleep. Half of all night shift workers regularly report dozing off and falling asleep when they are working. This should be seen as an important concern both for individuals and society, given that airline pilots, nurses, police, and other public safety workers are all employed in professions in which peak functioning during a night shift is crucial.


Light is a known Zeitgeber, which means it is a ‘time giver’

Zeitgebers are external cues that sync with an individual’s biological clock rhythms, such as a 24 hour clock.

Jeanne Duffy and Charles Czeisler (2009) – Entrainment theory – when the biological rhythms are matched to their environmental triggers, such as circadian rhythms being set in response to external cues ( light ).

Strengths and weaknesses

Internal Influences of Sleep


Evidence from animals that the suprachiasmatic nuclei have a role in setting the biological clock.

The SCN was removed from hamsters, stopping their biological rhythms which suggested that their sleep-wake cycle had become random.

But if they transplanted SCN from other hamsters their rhythms start again and their cycles return to normal.

Evidence from Humans – A study by Miles et al (1977) looked at a blind man whose bodily rhythms were nearer to 25 hours – suggesting that circadian rhythms are governed by internal factors.

  • If people that do not perceive light reset their clock than the way light is received must be complex.

Li-You Chen et al (2015) – confirms that the pineal hormone melatonin is vital for controlling sleep – The study using rats found that early sleep deprivation ( ESD ) led to low melatonin levels – Way of prevention this reduction in children is to give them melatonin supplements.


Experimenting on animals can cause problems generalizing to humans, as animals are different from humans in most physiological as well as psychological ways.

Evidences relating to human blindness is weak – there are many individual differences in ‘being blind’ so it can be difficult to arrive at an outcome which could lead to universal explanations. – People with NLP blindness (no light perception) may perceive light and colors ( Rose, 2015 ).

External Influences of Sleep


Many practices applications support the claim of bodily clocks in humans. The understanding that zeitgebers help shift workers or travelers, for example by darkening their rooms in the daytime.

Ralph Mistlberger and Debra Skene ( 2004 ) – Light is the main way bodily rhythms are synchronized to the mammalian day and night timings. They suggest that social stimuli can be used as cue to time, linking to levels of arousal and how some ones activities affect how awake they are.

  • Compared to light as a zeitgeber, social cues are not as effective.
  • This evidences external cues acting as zeitgebers although light is the main.


The explanation relating to light as an external influence on sleep is a suggested weakness, as there are many differences in findings.

Siffre (1975) aimed to check the findings of studies that claimed a natural sleep-wake cycle lasted for 48 hours, while other studies suggested that it was nearer to an expected 24 hours.

This makes it harder to draw conclusions regarding the sleep-wake cycle, and the roles of zeitgebers when the results of studies differ from one another.

Studies like Siffre’s on sleep-deprivation are set in situations that are regarded as unnatural and so may lack validity.

There is a weakness in the way these studies are carries out, such as in studies in which participants were in a cave without zeitgebers, researchers used bright artificial lighting, which could have easily affected their sleep-wake cycle.

Disorders of Sleep – In Depth

Insomnia: The general definition of insomnia is that it involves problems in falling and staying asleep and the reductions in sleep quality.

  • This leads to sleep becoming non-restorative, thus leading to daytime tiredness.
  • This can affect a person’s daily and social functioning.
  • Lifestyle choices that include frequent flying can also affect bodily rhythms
  • Healthcare conditions such as mental or physical ill health can lead to insomnia – depression, stress, heart problems

Diagnostic criteria for Insomnia

These may include one or more of the following symptoms:

  • The time taken for sleep to onset is more than 30 minutes. (Sleep onset latency).
  • Time actually spent sleeping is less than 85% (Sleep efficiency).
  • Increased number of night time awakenings.
  • Symptoms must last for 3 or more times a week to be diagnosed with Insomnia.

The duration of Insomnia is important as well.

  • Transient Insomnia lasts for less than a week and is often related to situations such as short term stress and jet lag.
  • Chronic or clinical Insomnia lasts for more than one month and has a distressing and rather major effect on daytime and social work / functioning as a result of tiredness and irritability.

Primary Insomnia: Problems with the quality and the duration of sleep leading to excessive daytime tiredness without an obvious cause.

Secondary Insomnia: Problems with the quality and the duration of sleep leading to excessive daytime tiredness, caused by an already pre-existing condition, such as depression.

Narcolepsy: Known as one of the more ‘dramatic’ sleep disorders, narcolepsy refers to a ‘genetic’ condition which leads to the inability to control sleeping and waking.

It is characterized by four major symptoms:

  • Excessive daytime sleepiness with repeated short episodes of sleep during the day.
  • Cataplexy: a sudden loss of muscle tone when waking leading to collapse. Cataplexy can be brought by emotional arousal of any sort, such as laughter or sexual arousal.
  • Hypnagogic Hallucinations: Described as dreamlike experiences occurring during the period of wake and sleep.
  • Sleep paralysis: The inability to move, often occurring when waking up or falling asleep.

When people with narcolepsy fall asleep they shift directly into the REM sleep stage, rather than experiencing the normal sleep pattern of moving through the stages of slow-wave sleep first.

  • An explanation for narcolepsy could be a gene deficiency that is responsible for narcolepsy in dogs. This gene, on chromosome strand 12 ( Lin et al. 1999 ) is responsible for regulating receptors in the brain for a neurochemical known as orexin. Without these receptors orexin cannot function, which suggests that the lack of orexin and its receptor is the main constituent for narcolepsy in humans.
  • Genes can also explain narcolepsy, as in about 10% of people that suffer from the disorder, there are other family members who have the disorder aswell. This may relate to problems in the hypothalamus. Variations in Chromosome 6 ( known as HLA ) complex lead to narcolepsy.
  • Stress and trauma: Wayne Baker (1948) presented situational stress as an explanation for narcolepsy and produced a link between them.
  • Evolution: An advantageous technique for animals to stay very still as a survival characteristic. Narcolepsy might relate to human REM sleep, which has a survival value.

Freud’s (1900) Theory of Dreaming

Psychoanalysis is a theory of the human mind, therapy for mental distress, an instrument for research and a profession.

It was conceived in the late 1890s by the Austrian physician Sigmund Freud (1856-1959).

Three methods used in psychoanalysis:

Slip of the tongue: Moments when someone uses one word when meaning another

Free association: Someone is asked to say their thoughts out loud

Dream analysis: Uses free association alongside the usual description of the dream.

Freud’s patients told him about their problems and their disturbing dreams. Freud uncovered the meaning of their dreams to find out what exactly was wrong with them. He managed to explain why the patient had the problem and find a way to cure them.

 Psychoanalysis takes a long time because many dreams have to be related and many sessions must be undergone before an analyst can start to suggest what the dream might represent.

Freud’s theory of dreaming was known as ‘Dreamwork.’

He suggested that dreams have a manifest content, which is the story of the dream that the dreamer tells. In psychoanalysis, certain symbols in the manifest content can be used to discover what the latent content of the dream is. Dreams have a latent content, which is the underlying meaning of the dream – the hidden content. The latent content is what is hiding behind the manifest content. The latent content is what psychoanalysis tries to unravel, as it reveals many important things in the unconscious brain.

Condensation: many ideas appearing as one idea in a dream. These separate elements are important in uncovering repressed material so that one idea needs to be unpicked.

Displacement: something unimportant that seems important, in order to shift attention from what is really important.

Secondary elaboration: using muddled ideas from dream work to build a whole story. The dreamer will add bits to the dream when telling someone what it is about to try to make the dream make sense. This gets in the way of understanding the latent content of the dream.

The Evaluation of Dreamwork


  • It can access hard to reach information that cannot be easily reached as it is buried in the unconscious and is not known to the dreamer.
  • Accepted by the client, the patient usually agrees with the results, the results are helpful to patients, which means that it is valid.
  • The dreams are often presented by the client themselves.


  • The processes are hard to measure and test, as they are unconscious.
  • It is a highly subjective matter.
  • People cannot always recall their dreams.

According to Freud our mind is made up of three levels

– The conscious level

– The preconscious level

– And the unconscious level.

The Id: is buried in the unconscious mind untrue. It seeks pleasure from what we do and in order to fulfill the desires (it could be needs, wants, etc.) and for pleasure. ( Pleasure is achieved when a need or want is fulfilled ).

The Ego: seeks reality. It is in our conscious mind. However not all of the Ego’s operations are conscious, some of the Ego’s operations are in the unconscious mind. They are thoughts about ourselves.  It is an identity we create for ourselves, that could be false at times. It is basically what you think you are. The Ego is related to the Id – it seeks to pleasure the Id’s drives. For example, in the Id a person wants to be the best. So the Ego seeks to become the best, or believes they are the best.

The Super Ego: controls the Id’s impulses.

There are two systems in the super ego: The conscience and the ideal self. The conscience can punish the ego by causing the feeling of guilt. For example, if the ego gives in to the id’s demands, the superego may make the person feel bad through guilt. Guilt happens when a person’s behavior falls short of their ideal self. The super ego can also reward them through the ideal self when they behave ‘properly’ (what is proper is decided by the conscious mind, which can be affected by things like society) by making them feel proud. If a person’s ideal self is too high a standard, then whatever the person does represents failure. The ideal self and conscience are largely determined in childhood and parental values and how people were brought up.

Strengths and weaknesses of Freud’s theory


  • Used unique methods to uncover unconscious wishes and desires, which are hard to access.
  • Gathered in depth and detailed information about individuals, qualitative data about real life (valid data).


  • His sample was biased, worked with mainly well of Viennese families so it is not generelisable.
  • Again, Freud interpreted his findings, so they may be subjective.

Hobson and McCarley’s Activation-Synthesis Model of Dreaming.

In 1977, two biologists Hobson and McCarley came up with the ‘activation-synthesis model’ of dreaming that contested Sigmund Freud’s (1900) theory of dreaming. They believed that dreaming was for biological reasons, that dreams were random and had no significant meaning.

Understanding of neurons and neural activity is necessary for this theory

Neuron: A neuron is a cell in the nervous system that processes and sends information within the body, using chemical and electrical signals. The activity of neurons is central to how the brain and the body works. Neurons respond to stimulus in the environment.

Axon: The ‘cable’ that leads from a cell body of a neuron down to the terminal buttons that hold the neurotransmitter. Passes messages away from the cell body to other neurons, muscles or glands.

Impulse: The electrical signal that travels from the cell body of a neuron to the terminal buttons (down the axon), where it releases a neurotransmitter

Dendrites: Receives messages from other cells

Terminal branches: Form junctions with other cells

Neurotransmitter: A chemical at the terminal button of a neuron, which is released by the impulse and then goes into the synaptic gap.

Synaptic gap: The gap between the dendrites of one neuron and the next

Synaptic transmission: What happens when a neurotransmitter released by an impulse of one neuron goes across the synaptic gap and is taken up at the dendrites of another neuron.

How does the brain send signals?

 1. An electrical impulse is triggered from the cell of one neuron then travels down the axon to the end. The impulse is also called action potential.

2. When the impulse gets to the end of the axon it releases a chemical, called a neurotransmitter, which is found in the terminal buttons at the ends of the axons.

3. This neurotransmitter has to cross a gap, called the synapse or synaptic gap, to get to the dendrites of the next neuron to continue the message.

4. The neurotransmitter, released by the impulse, goes into the gap – where it could be taken up by the dendrites or could be lost.

5. If the receptors at the dendrites of the next neuron are ‘suitable’ to receive the neurotransmitter that is in the gap, then the chemical gets picked up.

6. The neurotransmitter sets off an electrical signal (by changing the chemical balance at the receptor) and then it drops back into the synaptic gap where it can be taken back up to be used again.

7. The receptors trigger an electrical impulse from the cell body, which then travels down to the end of the axon and eventually repeating the cycle.

Activation synthesis.

During REM sleep random neurons are activated because there are random impulses that give information as if it were coming from the senses. This is known as random activation and is the ‘activation’ part of the activation-synthesis theory. The brain then synthesizes the random thoughts and feelings into a story or a sequence in order to make sense of it, making up for the ‘synthesis’ part of the theory.

Linked to REM sleep.

Strengths and Weaknesses of the Activation-Synthesis Model of Dreaming


  • To test their theory, Hobson and McCarley did brain scans on cats and found that the areas of the brain that were activated were responsible for movement inhibition and sensory blockade. By doing brain scans they provided evidence for sensory blockade and movement inhibition.
  • This theory was very reliable because they researchers used brain scans to measure brain activity. If the experiments were repeated the same results would be found.


  • Dreams do have more meaning than activation-synthesis suggest, many people say they recognise parts of the dream from what has happened in their lives.
  • Lucid dreaming is when people are dreaming but know they are dreaming. Lucid dreaming has been tested and found to occur. It does not fit with activation-synthesis as it means dreams are controllable and not random.
  • Testing on cats may have lowered the generalisability of the study, as the mind of humans and animals differ in many ways.

Siffre (1975) Six Months Alone in a Cave

French geologist, Michel Siffre spent 6 months (179 days) in an underground cave in Texas ( Going in on the 14th of February, 1972 and coming out in September of the same year ). There was no natural light and in the absence of this zeitgeber biological rhythms become what is called free running. The cave was artificially lit, and Siffre could use a telephone to communicate with his colleagues and ask for the lights to be turned off when he went to sleep and turned on when he woke.

During his stay underground many of his physiological and psychological functions were measured, including his body temperature and weight, heart rate, blood pressure and his sleep-wake pattern.

The two key findings showed that:

  • Siffre’s sleep-wake cycle circadian rhythm extended from the normal 24-hours to between 25-32 hours, suggesting his ‘days’ became longer. When he emerged on his 179th day, in his terms it was only the 151st day.
  • His body temperature circadian rhythm was more stable. Even though it extended to about 25 hours, it remained constant. An outcome of this was that Siffre’s sleep-wake cycle became desynchronized from his bodily temperature rhythms. Under normal circumstances they are synchronized, so that people regularly go to sleep when their body temperature is falling and awake when our body temperature is rising.

Siffre’s main aim was to see what his natural circadian rhythm was. His aim was to investigate how astronauts would get on being isolated without any cues to daylight or time. He concluded that the body clock might be manageable, if erratic. However, the period of isolation in a confined space was not manageable. Space travelers would absolutely need companionship.

Time is not something humans work with and understand without external cues.

Strength and Weaknesses of Six Months Alone in a Cave.


  • Studies above ground have confirmed the findings of research in cave environments. Siffre’s study was also an experiment. He controlled key variables (extraneous variables) to observe their effects on the sleep-wake cycle. This helps create a causal relationship.
  • As he was underground for such a long time, he was able to gather vast amounts of qualitative and quantitative data, which produced a detailed record of his time. Siffre documented everything and logged all his results, which provided a fair amount of information about how the absence of light can affect the sleep-wake cycle.


  • There is an issue of validity relating to the study. It may be described as a case study as it is the study of one individual and therefore has unique features.
  • The study was criticized because lights cane on when Siffre woke up and went off when he went to sleep. They were bright lights and could have easily affected his internal body clock. Czeisler et al. (1999) used 24 volunteers kept in lower-level artificial lighting, which was switched on and off and off over a 20-28 hour cycle. They found that the day was closer to 24-hours. This is a weakness of Siffre’s study.