How Does Sleep Affect Mental Processes And Behaviour

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Sleep

Regular and naturally occurring altered state of consciousness that involves a loss of awareness and disengagement with internal and external stimuli

Characteristics and Patterns of Sleep

Two distinct states:

* NREM (non-rapid eye movement sleep)
* REM (rapid eye movement sleep)

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Occur in a continuous cycle.

Sleep Episode

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.

Sleep Cycle

Consists of a period of NREM sleep (but not necessarily all four stages) and then a period of REM sleep

* Lasts 80-120 minutes so we go through this approx. 4-5 times a night

REM Sleep

A type of sleep characterised by rapid eye movement, high levels of brain activity, and low levels of physical activity. Eyes move rapidly beneath eye lids.

* Irregular beta/beta like brainwaves
* REM periods lengthen and get closer together as the night progresses

Characteristics of REM Sleep

* Highly active brain and less active body
* Virtually paralysed, meaning most muscle movement is not possible
* Relatively light stage of sleep
* Vivid dreaming
* Makes up approximately 20-25% of sleep episode for most age groups
* Increases as sleep episode progresses
* Lasts little time near the start of sleep, but can last hours later on

NREM Sleep

A type of sleep characterised by a lack of rapid eye movement and is subdivided into three different stages

Characters of NREM Sleep

* Less active brain
* Physical movement is possible and body is seen as ‘more active’. Movement decreases over the progress of the stages
* Muscle movement possible
* Dreams can occur but often non-vivd. Dreams not frequently recalled
* Amount of this sleep is highest during first half of sleep cycle
* Approximately 75-80% of sleep and becomes shorter with each sleep cycle
* Subdivided into three stages

NREM Stage 1 Sleep

Drift in and out of true sleep. Gradually lose awareness of surrounding. Physiological changes indicate lowered arousal and hypnic jerks occur as muscles relax.

* Lasts 5-10 minutes.

NREM Stage 2 Sleep

Point in which you are truly asleep. Sleep is less easily disturbed than previous stage. Movements lesson, breathing becomes regular, BP and Body temp continue to drop, HR slower.

* Lasts 10-20 minutes

NREM Stage 3 Sleep

Start of deeper period of sleep (moderately deep sleep). Physiological responses continue to slow. Less responsive to outside world, difficulty to wake and are groggy and disoriented if woken

* Lasts approx. 10 minutes
* Theta and

REM Paradoxical Sleep

Internal body and brain active - shown through physiological measures such as:

* EEG → Irregular beta
* EOG → High
* HR, BT → High

External body relaxed - shown through physiological measures such as:

* EMG → Very low activity

May need REM to consolidate memories by strengthening neural connections

Brain Wave Patterns: Frequency

The number of brain waves per second

Brain Wave Patterns: Amplitude

The height of the peaks and troughs of the curved graph that represents brain wave activity

EEG → ElectroEnephaloGraph

Detects, amplifies and records electrical activity of the brain. Small electrodes are attached to the surface of the scalp at the top and sides of the head in order to detect electrical activity.

* Alternatively, a swimming cap device could be worn

EOG → ElectroOcularGraph

Detects, amplifies and records electrical activity of the muscles that move the eyes. Electrical activity is produced by the muscles that control eye movements. This device can therefore measure eye movements and eye position. This is done by attaching electrodes to areas of the face surrounding the eyes

* Used to measure changes in eye movements over time during different stages of sleep and while dreaming

EMG → ElectroMyoGraph

Recording generally show strength of electrical activity occurring in the muscles, which indicates changes in muscle activity and muscle tone. Information about electrical activity is obtained by attaching electrodes to the skin above the muscles which are to be monitored

Brain Wave: Beta

Frequency: High

Amplitude: Low

Brain Wave: Alpha

Frequency: High (but lower than beta)

Amplitude: Low (but higher than beta)

Brain Wave: Theta

Frequency: Medium

Amplitude: Medium-high

Brain Wave: Delta

Frequency: Low

Amplitude: High

Video Monitoring

The use of camera and audio technologies to record an individual as they sleep. Useful for individuals with sleep disorders as their behaviours can be observed as they sleep.

Sleep Diaries

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

Information That Can Be Recorded By Sleep Diary

* 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
* The number of times sleep was disrupted

Biological Rhythms

Changes in bodily functions or activites that repeat through time in the same order. Examples:

* Blood sugar levels
* Digestive secretions
* Body temperature

Circadian Rhythm

A biological rhythm that involves changes in bodily functions or activities that occur as part of a cycle with a duration of about 24 hours

* Most extensively studied, and happens due to both internal and external factors

Ultradian Rhythms

A biological rhythm that involves changes in bodily functions or activities that occur as part of a cycle shorter than 24 hours

* Sleep cycle

Infradian Rhythms

Cycles that last longer than a day

* Menstruation

SCN → Suprachiasmatic Nucleus

An area of the hypothalamus that is responsible for regulating an individuals sleep-wake patterns. Regulates the timing and activity of the sleep-wake cycle. Receives both external and internal cues. Receives information about the amount of incoming light from the eyes and adjusts our sleep-wake cycle accordingly. Sends messages to the pineal gland to release less or more of the hormone melatonin into the blood.

SCN → External Cues

Involves information from the environment, such as the presence or absence of light

SCN → Internal Cues

Involve information that originates within the body (such as the expression and suppression of particular genes, known as clock genes)

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Melatonin

A hormone released by the pineal gland typically at night-time to induce sleep as part of the sleep-wake cycle

Summarising Steps of the SCN Process

1 → SCN receives external and internal cues

2 → SCN sends neural messages to the pineal gland to produce and release melatonin

3 → The pineal gland releases melatonin into the blood stream which promotes feelings of calm and relaxation, therefore promoting sleep

Sleep Across The Lifespan

Many characteristics of sleep that can change over the lifespan, those characteristics being:

* Sleep onset
* Sleep duration
* Awakenings during sleep
* Proportions of REM sleep
* Proportions of NREM sleep

Neonatal Stage

Sleep duration is the highest it will ever be, approx. 16 hours. 50/50% of each sleep episode is REM/NREM sleep.

* Lifespan from 1-15 days old

Infancy Stage

Sleep decreases est. to 13.5 hours. Proportion of REM and NREM sleep in sleep episode changes to 35% and 65% respectively

* Lifespan period 3-24 months of age

Childhood Stage

Sleep period decreases again to est. 11 hours. NREM sleep period increases to 80% per sleep episodes. Variations of the amount of REM and NREM as this age period is quite expansive

* Lifespan period of 2-14 years

Adolescence Stage

Sleep duration decreases to est. 9 hours. REM and NREM period remain consistent in each sleep episode est. 20% and 80% (respectively). Experience biological delayed sleep onset, meaning sleepier later and wake up later

* Lifespan period of 14-18 years old

Young Adulthood and Middle Adulthood

Sleep period duration decrease to 7.75 hours. REM and NREM stay 20& and 80% (respectively)

* Lifespan age period of 18-30 (young adulthood) and 30-75 (middle adulthood)

Old Age Stage

Duration of sleep decreases to approx. 6 hours. REM and NREm stay 20% and 80% (Respectively). Experience advanced sleep phase syndrome, which is a biological shift forward in sleep-wake cycle, meaning they become sleepier earlier and wake up earlier

* Lifespan period of 75+

Brainwave During Stage 1 of NREM

Alpha-theta brainwaves

Brainwave During Stage 2 of NREM

Theta brainwaves

Brainwave During Stage 3 of NREM

Delta brainwaves

Brainwaves During REM Sleep

Beta-like brainwave

Brainwave While Awake

Beta Brainwaves

Brainwaves During Drowsiness

Alpha Waves

Brainwaves During Stage 4 of NREM

Delta Waves