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What are the two states of consciousness
Normal waking consciousness (NWC): A state of consciousness in which an individual is awake and aware.
Altered state of consciousness (ASC): a state of consciousness that is distinctly different from normal waking consciousness in terms of quality of experience and levels of awareness.
What are the two types of altered sates of consciousness (ASC)
Altered states of consciousness (ASC) Definition
Naturally occurring altered state of consciousness A type of altered state of consciousness that occurs without intervention. (Sleep, daydreaming)
Induced altered state of consciousness A type of altered state of consciousness that occurs due to a purposeful action or aid. (Meditation, hypnosis)
What is the consciousness continuum
The consciousness continuum is a visual representation of the different states of consciousness that progress from lower levels of awareness to higher levels of awareness. Within the consciousness continuum, the two different types of consciousness (ASC and NWC) are presented.
What is sleep
Sleep is a regular and naturally occurring altered state of consciousness that involves a loss of awareness and disengagement with internal and external stimuli.
Why is sleep considered a psychological construct
Sleep can also be considered a psychological construct. This is because the subjective experience of sleep cannot be overtly measured, yet we still have a general understanding of what it is and that it exists.
What are some of the characteristics of sleep
• A reduced ability to control behaviour
• A reduction in the control we have over thoughts, for example, we lack control over what we dream about
• Less accurate understanding of the passage of time
• Perceptual and cognitive distortions
What are the different states of sleep
REM (Rapid Eye Movement)
NREM (Non-Rapid Eye movement)
What is REM
REM (rapid eye movement) sleep is a type of sleep characterised by rapid eye movement, high levels of brain activity, and low levels of physical activity. Specifically, REM sleep involves low levels of somatic nervous system activity, meaning there are low levels of movement in this stage
What is NREM
NREM (non-rapid eye movement) sleep is a type of sleep characterised by a lack of rapid eye movement and is subdivided into three different stages.
What is a sleep episode
A sleep episode is the full duration of time spent asleep. A sleep episode is made up of multiple
repeated cycles of REM and NREM sleep, called sleep cycles.
What is a sleep cycle
A sleep cycle is an approximately 90-minute-period that repeats during a sleep episode in which an individual progresses through stages of REM and NREM sleep.
What are the three stages of NREM sleep
NREM Stage 1 NREM Stage 2 NREM Stage 3
When moving into stage 1 of NREM sleep, the sleeper transitions from being awake into a light sleep. This transition is signified by the experience of the hypnagogic state, in which some people experience feelings of floating or falling, or a sudden jerk (referred to as a hypnic jerk). In this stage, the sleeper loses awareness of themselves and their surroundings but is still aware of faint sounds in the environment. The sleeper can be easily woken in stage 1. In stage 2 of NREM sleep, the sleeper is still in a relatively light sleep. Individuals spend the majority of their time asleep in NREM stage 2. In this stage, the sleeper is considered ‘truly’ asleep, due to the types of brain waves occurring. Brain waves are explored in the next lesson In stage 3 of NREM sleep, the sleeper is in a deep stage of sleep. It is difficult to wake the sleeper in this stage of NREM. If the sleeper is woken during this stage they are likely to feel drowsy and disoriented. During this stage, sleepwalking and sleep talking are most likely to occur.
What are the characteristics of the two types of sleep
Characteristics of REM sleep Characteristics of NREM sleep
Brain activity
The sleeper is considered to have a highly active brain during REM sleep. The sleeper is considered to have a less active brain than normal waking consciousness.
Eye movement
The eyes move quickly and dart in various directions, known as Rapid Eye Movements (REMs). These movements are linked to the visual experiences in dreams Slow eye movements (SEMs) occur, particularly during stage 1. As sleep progresses into deeper stages, these movements become less frequent and are nearly absent in stages 3 and 4.
Physical movement
The sleeper is virtually paralysed during REM sleep, meaning that most muscle movement is not possible Muscle movement is possible in NREM sleep, therefore the body is said to be ‘more active’ in this stage of sleep. However, movement tends to decrease as NREM stages progress.
Depth of sleep
REM is a relatively light stage of sleep; despite the muscle paralysis, the brain is active, and sleepers can be woken fairly easily. NREM sleep deepens with each stage, eventually reaching slow-wave sleep, which has low-frequency, high-amplitude brain waves. The deeper the stage, the harder it is to wake someone.
Occurrence of dreams
Vivid dreaming tends to occur during REM sleep. The sleeper frequently recalls dreams when woken during REM sleep. Dreams can occur in NREM sleep but they are often non-vivid. They often do not recall dreams when woken during NREM sleep.
Percentage of sleep episode
REM sleep makes up approximately 20–25% of a sleep episode for most age groups. NREM sleep makes up approximately 75–80% of a sleep episode and NREM sleep tends to become shorter with each sleep cycle
Time
The amount of time spent in REM sleep increases as the sleep episode progresses, with the largest amount of REM in the sleep cycle occurring immediately before waking The amount of time spent in NREM sleep is highest during the first half of a sleep episode and tends to get shorter further in the sleep episode.
How can sleep be measured
The measurements that are commonly used for consciousness can often be used to measure sleep as well. States of consciousness cannot be directly measured or observed, so they are inferred from other information instead, such as physiological responses or an individual’s behaviour. Some ways this information can be gathered is through analysing the objective physiological changes that occur during sleep or exploring qualitative information about changes that occur during sleep.
List some measures of consciousness and sleep
• the electroencephalograph (EEG)
• the electromyograph (EMG)
• the electro-oculography (EOG)
• sleep diaries
• video monitoring.
Describe objective measurement of sleep and their limitations
EEGs, EMGs, and EOGs are considered to be objective physiological measures. This means that they provide reliable, unbiased, quantitative data that can indicate someone’s state of consciousness. However, they do not provide qualitative detail about the personal experience of sleep, such as an individual’s thoughts or feelings. Additionally, changes in physiological responses may be due to factors other than a change in consciousness, thus the findings may lack validity at times.
Describe subjective measurements of sleep and their limitations
Sleep diaries and video monitoring are considered to be subjective measures. This means that information is provided by an individual and is related to their personal experiences. In this way, subjective measures do not provide a direct observation and the accuracy and reliability of such measures can be limited due to their subjective nature. Subjective measures can provide both qualitative and quantitative data such as sleep diaries but regardless both the types of data are considered unique to the individuals experience.
What’s another limitation to measuring sleep
Measuring sleep can be difficult as some techniques can be disruptive, invasive, or may require an individual to sleep in a sleep laboratory for a period of time. Changes to an individual’s regular sleep patterns, such as having to record their sleep or having electrodes attached to their head whilst asleep, can influence the quality and quantity of an individual’s sleep. Therefore, sleep measures may not provide a true reflection of an individual’s usual sleeping patterns.
What is an electroencephalography (EEG) and how does it work
An electroencephalograph (EEG) detects, amplifies, and records the brain's electrical activity, which occurs when neurons emit electrical impulses. These impulses are shown as brain wave patterns on the EEG. Different brain wave patterns correlate with various states of consciousness, allowing the EEG to identify different sleep stages based on these patterns.
How do brain waves vary
Brain waves vary in frequency (rate) and amplitude (height). Frequency is the number of brain waves that occur per second, whilst amplitude is the intensity and height of the brain waves. The frequency and amplitude of brain waves can indicate what state of consciousness an individual is experiencing.
Compare frequency and amplitude terms of wakefulness and sleep.
Frequency Amplitude
Indicator of
Frequency refers to the rhythmic fluctuations in electrical activity within the brain, where the waves repeatedly rise and fall. It reflects the speed of neuronal firing. Amplitude is an indicator of the strength or intensity of brain wave activity.
When Low Low-frequency waves (e.g., delta waves) indicate slower, more synchronized brain activity, associated with deep sleep and restorative processes. Low amplitude indicates weaker, more desynchronized neuronal activity, typical of wakefulness or lighter sleep stages.
When High High-frequency waves (e.g., beta waves) indicate rapid, active brain activity associated with wakefulness and alertness High amplitude in brain waves indicates strong, synchronized neuronal activity, often seen during deep sleep stages like slow-wave sleep.
How do EEGS identify different states of consciousness
EEGs can indicate whether an individual might be in an altered state of consciousness and therefore whether they may be asleep. Often, an EEG will show a higher frequency and lower amplitude when in normal waking consciousness, and a lower frequency and higher amplitude during an altered state of consciousness.
State a strength and limitation of EEGS
A strength of EEGs for sleep studies is their usefulness in diagnosing sleep disorders and brain conditions. However, a limitation is that EEGs measure neural activity through the skull, making them less precise, and they do not pinpoint specific brain areas as accurately as neuroimaging techniques like fMRI.
The types of brain waves
State the frequency and amplitude in each sleep stage in order
REM: This stage consists of the highest frequency and lower amplitude in a sleep episode. An EEG will show beta-like brain waves, as the brain is highly active in REM sleep
NREM 1: This stage consists of a high frequency and low amplitude in NREM sleep stage 1 (transitioning from wakefulness to sleep), but lower frequency and higher amplitude than normal-waking consciousness. (Alpha like brain waves)
NREM 2: This stage consists of a medium frequency and medium amplitude (light sleep) and will often show theta-like brain waves. During NREM sleep stage 2, the sleeper is considered truly asleep.
NREM 3: This stage consists of a lower frequency and higher amplitude (slow wave sleep) and will often show delta-like brain waves.
What is an electromyograph
An electromyograph (EMG) is a device that detects, amplifies, and records the electrical activity of the body’s muscles. By attaching electrodes to the skin above the muscles under investigation, the movement and tension of muscles (muscle tone) are recorded. Sometimes the activity in facial muscles is recorded. At other times, leg muscles, muscles on the torso (main part of the body), or a combination of these are recorded.
Explain how an EMG works
Muscle movement and tension can be used to identify the different stages and types of sleep an individual may be experiencing through gathering information about how active a person’s muscles are.
Compare EMG activity in REM and NREM sleep
During REM sleep, EMG readings show low activity as most muscles are effectively paralysed However, some small, involuntary movements, such as twitching of fingers or facial muscles, can still occur, hence the low activity.
During the lighter stages of NREM sleep (1/2), moderate/medium muscle activity can be detected, and movements such as shifting positions or slight muscle twitches are common. As NREM (3) sleep progresses into the deeper stages muscle activity becomes lower, but some movements can still occur, though they are less frequent and usually less pronounced.
What is an electrooculography (EOG)
An electro-oculography (EOG) is a device that detects, amplifies, and records the electrical activity of the muscles surrounding and responsible for eye movement. The movement of these muscles, and therefore movement of the eyes, is measured by electrodes that are attached to the skin above the eye muscles.
How does it work
Eye movements, which are facilitated by the movements of muscles surrounding the eyes, are a physiological response that can be used to investigate the type of sleep a person is experiencing. One of the main distinguishing features of REM sleep and NREM sleep is eye movement. Therefore, EOGs are helpful in determining what type of sleep an individual is experiencing.
What can be observed during REM and NREM movement
• During REM sleep, an individual experiences rapid eye movement, so an EOG is likely to show high activity.
• During NREM sleep, an individual does not experience rapid eye movement and rather show slow eye movement (SEMS), so an EOG is likely to show low activity. It is likely that eye activity decreases as an individual goes deeper into sleep.
What are sleep diaries
• Sleep diaries are a record containing self-reported descriptions from an individual about their sleeping periods, including an estimated time spent sleeping and judgements they might have about the quality and nature of their sleep.
• It can include both qualitative and quantitative information. This information is recorded over a period of time, most commonly a few weeks.
• This method is subjective and therefore can be less reliable than objective measures, such as EEGs, as individuals may not be able to determine the exact time they fell asleep or be able to remember the quality of their sleep upon waking
What type of information can be recorded in sleep diaries
• The duration of sleep
• The quality of sleep
• Thoughts and feelings before going to sleep
• Thoughts and feelings after waking up
• Behaviours before going to sleep
• Behaviours after waking up
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