U4 AOS 1 - Sleep

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Sleep

naturally occurring and reversible altered state of consciousness, characterised by a reduction in awareness and responsiveness to external surroundings.

Split into NREM Non rapid eye movement
N1- light sleep

N2 - deeper sleep

N3 - deep sleep

and REM rapid eye movement (dreaming)

Consciousness

Consciousness is the awareness of your own internal mental processes, including your thoughts, feelings, sensations and perceptions, and your awareness of the external world around you.

can consciousness be observed

no

psychological construct

A mental process that cannot be directly observed and measured through the collection of data.

consciousness requirements and existence

• • We believe consciousness exists; however, we can only indirectly measure it through qualities that are more easily assessed, such as physiological changes or observable behaviours, or through self-report methods.
    
    

• Constructs however, DO need to be supported by research evidence.

normal waking consciousness

being aware of our internal and external environments we are awake and aware of regular levels of awareness in everyday activities.

altered states of consciousness

an altered state of consciousness is any state that differs in awareness from normal waking consciousness. 

our levels of awareness are lower or higher than in normal waking consciousness.

natural occurring and induced

naturally occurring altered states of consciousness

Naturally occurring altered states of consciousness occur without any external influence, such as sleep or a state of fatigue.

Induced altered states of consciousness

Induced altered states of consciousness are brought about on purpose, such as an alcohol-induced state, an anaesthetised state for an operation or a meditative state.

Sleep percentages

NREM —> 80%

REM —> 20%

how many sleep cycles,

8 hours, 5 sleep cycles, 90 minutes

nrem

• Non-rapid eye movement (NREM) sleep is a type of sleep characterised by a progressive decline in physiological activity. 

NREM sleep consists of three distinct stages and takes up around 80% of a sleep episode in people of school age and older.

nrem 1-

Induced altered states of consciousness are brought about on purpose, such as an alcohol-induced state, an anaesthetised state for an operation or a meditative state.

• It is the period when a person ‘dozes off’ to sleep and when they may most easily be woken up. 

• As a sleep episode progresses, a person may not experience much more time in N1. 

• If they are not disturbed for a couple of minutes in N1, a person quickly moves into NREM Stage 2 (N2).

• NREM Stage 2 (N2)

• is also considered light sleep, during which physiological responses continue to slow down. 

  • A person still wakes relatively easily during N2; however, bursts of brain activity help resist being woken by environmental stimuli such as noises. 

N2 is the stage of sleep that is experienced the most throughout a sleep episode.

• NREM Stage 3 (N3)

• NREM Stage 3 (N3) is considered to be deep sleep, during which physiological responses are at their slowest and a person is most difficult to wake up. 

  • N3 is known as ‘slow-wave sleep’ due to brain activity being at its slowest. 

  • During a sleep episode, N3 is experienced more in the first half of the night than the second half of the night. 

  • As a sleep episode progresses, a person experiences less N3 sleep, and may not experience it at all in the last one or two sleep cycles of a typical night. 

  • It is thought that our body is repairing itself during NREM sleep.

REM rapid eye movement sleep, what is it

• During rapid eye movement (REM) sleep, your eyes make quick darting movements behind their closed eyelids and your physiological activity increases. 

  • During REM sleep, brain activity resembles wakefulness, and heart rate and breathing rate increase. 

  • Voluntary muscles are seemingly paralysed and twitch only intermittently. 

  • The most vivid and memorable dreams occur during REM sleep. 

REM periods/durations and purposes

• A period of REM occurs at the end of each sleep cycle, and these periods get longer and closer together as the sleep episode progresses, which means you have more REM in the second half of sleep than in the first half. 

• REM sleep also differs markedly across different ages, but typically takes up 20% of a sleep episode in people aged around 5 years and older. 

• If you have less sleep than normal, you may experience more REM sleep when you next sleep. 

• It is thought that our mind is repairing itself during REM sleep.

Hypnogram

• A hypnogram is a line graph of a person’s sleep mapped over time. 

• A hypnogram displays the sleep architecture or patterns of a sleep episode, with a typical night’s sleep for an adult consisting of five sleep cycles featuring REM and NREM sleep. 

• Time (in terms of the time of a 24-hour day or hours since attempting to sleep) is plotted on the horizontal x-axis. The types and stages of sleep are shown on the vertical y-axis, with wakefulness at the top and deepest sleep at the bottom. 

• Therefore, a hypnogram shows how a person’s sleep progresses through several sleep cycles consisting of REM sleep and the three stages of NREM sleep, over the course of a night.

objective sleep measurements

can have measured evidence to support it.

Electroencephalography (EEG)

• An electroencephalograph detects, amplifies and records electrical activity of the brain (brainwaves)

• Non-invasive brain imaging technique that uses scalp electrodes to measure the voltage fluctuations induced by the mass electrical activity of neurons

• The image it produces is an electroencephalogram

• Brainwaves can be measured in both frequency (the speed - the number of brain waves per second) and amplitude (the strength - the deviation from the central point)

• Brainwaves are associated with the level of alertness we experience

when frequency highest, amplitude lowest

• Normal waking consciousness

• Awake, alert and focused

• High environmental stimulation

• Brain working on several things at once

when frequency and high, amplitude low

• Lower alertness

• Awake but relaxed

• Drowsy

• Low environmental stimulation

frequency low, amplitude high,

• Low alertness

• Light sleep

• Senses withdrawn from the external environment

• Deep meditation

frequency lowest, amplitude highest

• Lowest alertness

• Deep N3 sleep

• Dreamless sleep

Electromyography (EMG)

Detects, amplifies and records the electrical activity of the skeletal muscles

• Can be used on face or body muscles

• The image it produces is an electromyogram

• Muscle movement/tension can be measured in both frequency (the speed) and amplitude (the strength)

• In general, more muscle tension indicates greater alertness, so as a person drifts into deeper sleep, muscle movement decreases. 

Additionally, no muscle movement is detected during REM sleep.

Electro-oculography (EOG)

• This device detects, amplifies and records electrical activity of the muscles that allow the eye to move (it therefore only infers eye movement)

• The image it produces is an electro-oculogram

• ‘Eye-movement’ can be measured in both frequency (the speed) and amplitude (the strength)

• It is measure by placing electrodes around the eye

• Activity levels of ‘eye-movements’ are associated with different stages of sleep

• As you drift into deeper sleep, your eye movement decreases and slows down, and when you experience REM sleep, your eye movement increases.

Subjective sleep measurements

→ subjective descriptions of altered states of consciousness, sleeep

Sleep Diaries

• Sleep diaries are often used when a person is experiencing sleep troubles (e.g sleep apnoea or insomnia) and help sleep experts understand the participant’s experience.

• They are a self-reported record of an individual’s sleep & waking time activities.

• Records can be kept of:

  • Time trying to fall asleep

  • Number, time and length of awakenings during sleep

  • How sleepy the individual feels at different times of the day

  • Factors that affect sleep e.g. number of caffeinated or alcoholic drinks consumed

Video monitoring

• Video cameras are used to record externally observable physiological responses throughout a sleep episode

• Recordings can also be shown to the participant to help them become aware of and understand their behaviour, for example, showing what they do when sleepwalking or even observing the effects of a snoring partner on their sleep.

• Records may be kept of:

  • Changes in posture or body position

  • Amount of ‘tossing and turning’ restlessness

  • Sleep-related breathing problems (e.g. sleep apnoea)

  • What happens when awakening from a nightmare or night terror

  • Behaviour associated with sleepwalking

advantages when measuring consciousness/sleep of objective data

• data is quantitative, which is easy to measure and compare. 

• minimal interpretations required, thus minimises bias.

• more accurate and reliable data, allowing for replication.

disadvantages when measuring consciousness/sleep of objective data

• can lack detail, as no insight gained as to why responses/measurements are obtained.

• can be more artificial and lack external validity because measurements are taken in a laboratory.

• cannot describe private and personal thoughts

advantages when measuring consciousness/sleep of subjective data

• provides qualitative data, thus is more detailed.

• can provide insight into mental processes that cannot be directly measured.  eg. dreams.

disadvantages when measuring consciousness/sleep of subjective data

• qualitative data, means it can be difficult to measure and compare.

• requires personal judgements/ interpretation, meaning it is often influenced by bias 

• it is less valid and reliable due to bias and therefore, more difficult to replicate.

Circadian Rhythyms

Biological processes that coordinate the timing of activity of body systems over a 24 hour period

Ultraradian Rhythms

Biological processes which coordinate the timing of things less than 24 hours

Sleepin in terms of circadian and ultrradian

Wakefulness and sleep is circadian

Individual sleep stages is ultraradian

Suprachiasmatic nucleus (SCN) and influences

The suprachiasmatic nucleus (SCN) is found in the hypothalamus.
“master body clock”

influenced by external cues, known as zeitgebers, such as light, exercise, social acitivity, eating patterns and temperature.

zeitgebers

external cues influencing circadian rhythm the SCN, such as light, exercise

melatonin

the sleep hormone,more makes you drowsiness,

pineal gland

the glang producing melatonin which makes you feel drowsy

how melatonin produced

when low/no light detected by light sensitive neurons in retinas, → SCN suprachiasmatic nucleus, sends excitatory signal to pineal gland in human brain => the pineal gland releases melatonin

how melatonin inhibited

opposite of above flashcards,

detect more light → scn, sends inhibitory messages to pineal gland, inhibits release by pineal gland

SCN and melatonin levels in blood (internal stimulus)

when melatonin levels in the blood are high, the SCN signals to the pineal gland to reduce the secretion of melatonin.

negative feedback loop, stabilise body internal environment by opposing and counteracting of internal or external stimuli.

regulatory mechanism, where the output of a sytsem reduces or slows down the processes that led to that output, thus stabilizing the system.

Light Cues changing circadian rhythm

without light cues, circadian rhythm tends to run free and cycle for a little longer.

What does the total amount of sleep do across a lifespan

Decrease

Proportion of REM sleep X’a significantly from birth till 2

Decreases

Across lifespan, N3 trend and N2 trend

N3 sleep decreases, Replaced by N2 sleep

Adolescents go to sleep later, what is that called

Preference for going to sleep later

After adolescence, adult, going to sleep earlier, what called?

Circadian phase advance

Awakenings

Waking up from sleeping

Awakenings do what from adulthood to old age

Increase

Sleep efficiency

The percentage of time in bed that is spent asleep

Sleep efficiency over lifetime

Decreases

Neonatal period

0-1 month

Neonatal recommended hours and proportion of REM and NREM

14-17 hours

REM 50%

NREM 50%

Each episode lasts between 2-4 hours

Why is there a lot of sleep

Increase in amount of sleep for rapid growth development. Boost brain growth and development. , Muscle twitches in REM sleep typically immobile may be to help newborns develop their sensory motor system. 😭

infancy stage (age and rec hours and rem and nrem proportion)

2-12 months

13-15 hours,

each sleep episode, 5-8 hours

rem 35-40%

nrem 60-65%

explanation for infants,

→Infants begin to sleep for longer periods at a time as their circadian rhythm develops a more regular sleep pattern following day–night cycles.

This is due to the SCN and melatonin synchronising with a 24 hour circadian rhythm.

childhood stage

2-11 years

 - 11 hours

REM 20%

NREM 80%

explanation for childhood

From the early to late childhood years, the timing of the circadian rhythm gradually delays, and sleep shifts to later in the evening.

2 - 5 years old: N3 makes up more than half of NREM sleep.

6 - 10 years old: N1 and N2 sleep increases and N3 decreases

adolescence stage

11-18 years


8 - 11 hours

(early adolescence sleep is longer)

REM 20%

NREM 80%

explanation for adolescents sleep patterns

Adolescents experience a delay in the circadian rhythm because of a hormonally determined shift in melatonin release to 1–2 hours later than other age groups. This can cause a preference for a later bedtime, resulting in fewer hours of sleep than needed because of early waking for school.

In this age group, increasing school-related requirements, increasing independence and easy access to constant entertainment and social networks also contribute to delayed bedtime.

early to middle adulthood

19-50 years

7-9 hours

REM 20%

NREM 80%

early to middle adulthoodexplaninnation

Total daily sleep and proportion of REM is settled for the moment - decreases as we age. 

N3 continues to decrease and we spend more time in N1 and N2.

More frequent awakenings in middle adulthood.

Frequent awakenings and lifestyle choices (staying up, work, social pressure, alcohol consumption) leads to decreased quality of sleep.

older adult, age

50+ years

important pattenrs and explanation for older adults/elderly,
→ lifestyle changes?
→change to circadian rhythm
→changes to proportions of sleep?
→ changes to awakenings?
→sleep latency?

→melatonin?

Sleep patterns in older adults can alter because of lifestyle changes such as retirement, increased health issues including sleep disorders, physical inactivity, decreased social interactions, increased medication use, change of living arrangements and bereavement.

A circadian phase advance occurs, and less sleep may be achieved if a person resists the body’s preference for an earlier bedtime and earlier awakening.

Amount of N3 sleep continues to decline and may not occur at all, replaced with N2 sleep or more frequent awakenings.

During older adulthood there is an increase in sleep latency (the time taken to fall asleep).

Melatonin concentrations continue to decline.

The shorter total sleep in this stage may be due to the impaired ability to obtain sleep, rather than a reduced need for sleep.

sleep onset trends for all age groups,
neonatal
infants
children
adolescents
adults
elderly

Sleep onset (circadian rhythm determined)

• Neonatal (no circadian rhythm, many sleep episodes over 24 hours)

• Infants (circadian rhythm becomes established, longer sleep blocks overnight starting ~9-10pm, several naps during day)

• *Children (1-2 naps in early childhood, sleep onset gets earlier when naps are dropped 5-7 and shifts later again in late childhood ~7-8pm)

• *Adolescents (sleep onset moves later again ~9-10pm as circadian rhythm shifts later than both childhood and adulthood by a couple of hours)

• *Adults (varies but ~8-12pm)

• *Old age (varies but generally a bit earlier than when an adult)

sleep awakenings

Sleep awakenings

• Neonatal (many over 24 hrs, awake generally not longer than 20-90 min, sleeping pattern is erratic!)

• Infants (several short to medium periods awake to feed overnight for ~30-60 min overnight until ~6 months of age, awake periods between naps during the day)

• Children (occasional brief to short awake periods overnight)

• Adolescents & Adults (stays relatively the same/stable⇒ several brief awakenings overnight)

Old age (many more brief to short awakenings overnight )

Melatonin production and age

Neonatal

• minimal melatonin production 

• = no night/day cycle, mostly asleep with regular short period of being awake - SCN not active?

Infants 

• rapid increase in melatonin 

• = night/day cycle and establishment of circadian rhythm 

Children 

• melatonin still high = fewer but longer naps, and night sleep

Adolescents 

• melatonin starts to drop = puberty and night sleep only

• circadian rhythm delayed by 1-2 hours

Adulthood 

• Slow decline in melatonin

Old age 

• low melatonin production

why lower melatonin production in older people?

Older people:

• Cortisol levels lower = less blood glucose = less energy -> less active during day & significantly less active at night (maybe also less light entering eyes overall?) 

• Suprachiasmatic nucleus fires less during day and night = fewer messages to pineal gland to produce & release melatonin

• -> less melatonin produced during day and night, and ends earlier in night = less sleepy & less deep sleep, shorter duration sleep

*Still tend to spend the same amount of time or more time in bed compared to adults but less time sleeping effectively