UNIT 4 psych - sleep

Sleep

a reversible behavioural state of perceptual disengagement from and unresponsiveness to the environment.

• Reversible → sleeper can always be woken up with a strong enough stimulus

• Perceptual disengagement → no awareness of sights, sounds, smells and other sensory stimuli

• Unresponsive – sleeper not responsive to external environment

Sleep is a psychological construct

a concept that is ‘constructed’ (created/made) to describe specific ‘psychological’ activity (thoughts/feelings/behaviour), or a pattern of activity, that is BELIEVED to occur or exist but cannot be directly observed.

Biological rhythms

refer to naturally occurring patterns of cyclic changes in bodily functions or activities that repeat themselves through time in the same order.

• body temperature

• blood pressure

• sleep-wake cycle

• secretion of certain hormones

3 TYPES

Circadian rhythms, Ultradian rhythms, Infradian rhythms

Circadian Rhythm

biological cycle with a duration of approximately 24 hours

e.g. sleep-wake cycle

Suprachiasmatic nucleus (SCN) small part in hypothalamus → regulates the timing and activity of sleep-wake cycle & other circadian rhythms

SCN - has a pair of pinhead sized structures containing 20,000 neurons

Circadian Rhythm - The Sleep-Wake Cycle

SCN receives info about amount of incoming light from RETINA in eyes → adjusts sleep-wake cycle accordingly

• light is the MAIN environmental cue that influences the cycle

→ sends neuronal messages to pineal gland to produce less or more melatonin hormone (LESS light = MORE melatonin, MORE light = LESS melatonin)

Melatonin

Higher melatonin levels = greater drowsiness

Lower melatonin levels = greater alertness

• only comes out at night → from PINEAL GLAND

• artificial lighting can be bright enough to impede the release of melatonin.

• synthetic melatonin is sometimes prescribed to treat some types of sleep disorders.

Ultradian rhythms

biological cycle that is shorter than 24 hours

e.g. REM/NREM cycle

NREM sleep

non-rapid eye movement sleep → a ‘relatively inactive brain in a body that can move’

• accounts for 80% of total sleep

• slower and larger brainwaves → high amplitude, low frequency

• experience more NREM sleep in first half of the night

• REDUCTION IN PHYSIOLOGICAL ACTIVITY

• 3 stages - differ in physiological processes

• EEG → useful → each stage is identified by a specific pattern of brain wave pattern

Stage 1 - NREM Sleep ‘presleep stage’

A very brief, light sleep from which we can easily be awakened

• low arousal threshold (easy to wake someone up)

• average 5 minutes → can be (30 sec - 10 minutes)

• awake → hypnagogic state (relaxed)

  → may experience unusual hallucinatory type perceptual experiences (flashes of light and colour, vivid images, feeling floating)

  → hypnic jerks - involuntary muscle twitches causing jolts

Physiological changes

• decrease in heart rate

• decrease in respiration (breathing)

• decrease in muscle tension

• decrease in body temperature

→ gradual loss of self awareness and environmental awareness

→ decrease in alpha brain waves and replaced by irregular medium frequency theta brain waves (mix of high and low amplitude)

Stage 2 - NREM Sleep

‘truly asleep’

• period of light sleep (whilst it requires more intense stimuli to wake someone up than in Stage 1, the individual can still be easily aroused) → but HIGHER AROUSAL THRESHOLD than stage 1

• 10-25 minutes → lengthening with each successive cycle

• Accounts for approx. 45-55% of the total sleep episode, which is the bulk of an ‘average’ person’s sleep each night

Physiological Changes

• a continued lower level of bodily arousal:

  • Further decrease in heart rate

  • Respiration (breathing) becomes regular

  • Further decrease in body movements (muscles becoming more relaxed)

  • Further decrease in body temperature

  • Eye movements stop

→ Brain wave pattern is slower (predominantly theta waves)

→ Sleep spindles (brief bursts of higher frequency brain wave activity) of 1 to 2 seconds occur periodically – suggesting that the person is truly asleep.

Stage 3 - NREM Sleep

Deepest stage of sleep with the highest arousal threshold (difficult to wake)

• Typical duration is approx. 20-40 minutes and constitutes 10 to 15 % of our total sleep.

• As the night progresses, less and less time is spent in Stage 3 sleep.

• muscles are completely relaxed and barely move.

• when wake → they can feel very groggy and take several minutes to orient themselves (referred to as sleep inertia)

EEG Activity

• Delta waves dominate the EEG pattern.

• Delta waves may become even slower and larger than in Stage 3.

• Bedwetting, sleepwalking, sleep talking and night terrors tend to occur in stage 3 of sleep.

  → Night terrors → when someone wakes suddenly, ‘terrified’ and sweating profusely (differ from nightmares, as a person has little to no recall of their sleep terror episode).

NREM sleep to REM sleep

• progression through the first NREM sleep cycle from Stage 1 to 3 takes about 45 to 60 minutes, then we gradually move back through stages 2 and 1

• Once pass through one cycle of NREM sleep → unlikely to wake, BUT our brain and body begin to respond as if we are on the point of waking → this suggests about to move into REM sleep.

REM sleep

rapid eye movement sleep → ‘active brain in a paralysed body’

• faster and smaller brainwaves = low amplitude (height) high frequency (how often)

Physiological responses change during this stage

• Heart rate is faster and more irregular

• Respiration is typically faster and irregular

• Blood pressure rises

• Brain waves pattern typical of REM sleep is low amplitude

  and high frequency beta waves (this pattern resembles that of alert wakefulness)

→ 20-25% of total sleep

→ “paradoxical sleep” – internally the brain and body are active, externally the body is calm and inactive.

→ Occasional twitching of facial muscles, toes, fingers

→ paralysis → Generally skeletal muscles are limp and no outward signs of movement are observed

→ most dreaming during REM

features of sleep

• go through one cycle of NREM and REM sleep every 90 minutes.

• alternate between NREM and REM sleep throughout the night in a cyclical way.

• Most adults typically experience four to six NREM/REM cycles per night.

• The amount of time spent in NREM sleep gradually DECREASES as the night progresses whereas the amount of time spent in REM increases.

• There are significant physiological and psychological differences between the two stages of sleep.

measuring physiological changes

• EEG (Detects, amplifies and records the electrical activity of the brain (presented as brainwaves)

• EOG (Detects, amplifies and records the electrical activity of the muscles around the eyes)

• EMG (Detects, amplifies and records the electrical activity of muscle movements and tension)

psychological + behavioural changes

• sleep diaries - p

• video monitoring - b

Infradian rhythms

biological cycle that is longer than 24 hours

e.g. menstrual cycle

sleep latency

the time it takes for a person to fall asleep after the lights are turned off or after they get into bed with the intention to sleep

infants (0-2 years)

• rem → Highest proportion of REM (50% for under 3 months, 40% for 3-5 months, 30% for 1-2 years of age)

• nrem → (50-70%)

• total hours → 16 hours per day when a newborn, decreases to 12 hours per day when 2

children (2-13 years)

• rem → (25% decreases to 20-18% at 3) roughly 1.5 hrs per night

• nrem → (higher amount of than other age groups) → more time in stage 3

• total hours → 12 hours to 10 hours

Adolescents (13-18 year)

• rem → 20%

• nrem → less time spent in stage 3, stage 2 increases

• total hours → 8 hours roughly BUT should be 9

Adult (18-65 years)

• rem → 20/25% of rem

• nrem → gradual loss of stage 3 → men more than women

• total hours → 7-8 hours

older adults (65+)

• rem → 20% roughly per night

• nrem → reduced stage 3 compared to other groups

• total hours → 6 hours roughly per night

• PROPORTION OF REM REMAINS FAIRLY CONSISTEN FROM CHILDHOOD TO OLDER AGE AS LONGA S BEDTIME IS FIXED

sleep as a naturally occurring altered state of consciousness

describe any state of consciousness that is distinctly different from normal waking consciousness in terms of level of awareness and experience

• naturally occurring

  OR

• induced → meditation, hypnosis, alcohol, particular medications or illegal drugs

normal waking consciousness

refers to the states of consciousness associated with being awake and aware of objects and events in the external world, and of one’s sensations, mental experiences and own existence (internal world)

Sleep Disturbance

any sleep-related problem that disrupts someone’s sleep-wake cycle.

• difficulty falling asleep (sleep-onset)

• waking from sleep

• abnormal behaviour during sleep

occur regularly and cause distress or impairment, it is referred to as a sleep disorder.

Partial Sleep deprivation

the inadequate quality sleep and/or quantity of sleep

• → quantity - measured by the number of hours slept

  → quality - measured by how rested we feel (in words not rating

Effects of partial sleep deprivation

most sleep disorders associated with psd → occurs over a long period of time

• affective functioning - EMOTIONAL

  → amplified emotional responses,

  → increased emotional reactivity

  → inaccurate interpretation of facial expressions

  → reduced empathy

• behavioural functioning - VISUAL

  → sleep inertia → interfere with simple tasks

  → excessive sleepiness

  → fatigue + lack of energy

  → involuntary lapses into microsleep

  → impaired regulation of behaviour → increased risk taking

• cognitive functioning - MENTAL

  → reduced alertness

  → difficulty performing simple tasks + making decisions

  → impair learning and memory processes

  → some hand eye coordination

microsleep

sleep episode that lasts for a few seconds up to 10 seconds

• briefly close their eyes partially or fully, can also occur with eyes open

• common characteristics are a blank expression on the face and a nodding head

sleep inertia

a temporary period of reduced alertness and performance impairment that occurs immediately after awakening

→ strongest at wake time

cognitive impacts of BAC of 0.05 and 0.10

• 17 hours of total sleep deprivation (sustained wakefulness) = Blood alcohol concentration of 0.05%

• 24 hours of total sleep deprivation (sustained wakefulness) Blood alcohol concentration of 0.10%

Delayed sleep phase syndrome

The major sleep episode is delayed in relation to the desired sleep time or what is considered a conventional time

→ natural tendency to go to sleep 2-3 hours later and therefore wake up later than what is normal according to ‘society’s clock’.

→ only an issue if individual is not able to sleep in and gain their required hours of sleep

→ if interferes with school/ other routine activities → compensate with napping + sleeping excessively ion weekends → temporary relief → perpetuates delayed sleep phase

Symptoms

• sleep-onset insomnia

• difficulty awakening at the desired/necessary time

• excessive sleepiness

DSPS in Adolescents

• tends to emerge/worsen during adolescence + continue into early adulthood

  → 7-15% of them, affects both males and females equally

• most common circadian rhythm phase disturbance

  → BIOLOGICAL CAUSE → involves later release of melatonin

  → SOCIAL CAUSE → social pressures (studying, socialising, part time)

  → PSYCHOLOGICAL CAUSE → not wanting to go/willpower

Advanced Sleep Phase Disorder

disorders occur over a long period of time, cause distress +/or dysfunction, advance of the major sleep episode to an earlier time compared to desired or conventional sleep times

• results in compelling evening sleepiness, early sleep onset, and awakening earlier than the desired or necessary times.

• keep going to bed and waking up too early because of their difficulty or inability to remain awake or asleep until they want to

• sleep onset between 6pm and 8pm → wake up 1am and 3 am

• generally have less difficulty maintaining school, work, or social requirements since societal norms fit more easily into the sleep–wake schedule associated with ASPD

ASPD IN old people

• more common among older people 1%

  → may be due to age-related deterioration in the biological clock (SCN) → regulates the sleep–wake cycle

  → reduction in melatonin production

  → shift in the circadian timing of melatonin secretion to 2–4 hours earlier than normal → decreased exposure to light in late afternoon + more light in mornings

Shift work disorders

a circadian rhythm disorder caused by work shifts regularly overlapping the usual sleep period.

symptoms

• insomnia (struggle trying to go to sleep - reduction in melatonin and light)

• excessive sleepiness (when trying to be awake and alert)

• a reduction in total sleep time (deprivation - 1-4 hours less)

swd in shift workers

• 16% of Australian employees follow a shift work schedule in their main job that is outside the 9am-5pm timeframe.

• Night shift workers:

  - generally sleep 1-4 less hours than those who do not

  - often sleep in two smaller chunks during the day (resulting in lighter and disrupted sleep leaving them feeling unrefreshed)

  - revert to daytime routines on their day off which further disrupts their sleep-wake cycle

Bright Light Therapy (BLT)

• used to treat circadian rhythm phase disorders

• 2500 lux to 10000 lux

• aim is to re-set the biological clock regulating a person’s sleep-wake cycle to align it with the sleep-wake schedule required or desired

  → involves timed exposure of the eyes to intense but safe amounts of artificial light

  → 15 min to 2 hrs once or twice a day

blt to fix circadian disorders

• DSPS → woken up early with blt 30 min and then before bed NO LIGHT → advance the circadian rhythm to an earlier time

• ASPD → light exposure during early at night → DELAY circadian rhythm to a later time → sleepier later and wake up later

• SHIFT WORK → use the blt before whenever they need to be alert + avoid daylight between end of the shift and sleep time (dark sunglasses + goggles)

ZEITGEBERS

environmental time cues

• sunlight - main cue

• light

• food and drink (eating patterns)

• temperature

• alarms, school bells, routines ( anything that can symbol TIME)

ENTRAINMENT

→ when the SCN adjusts or resets the sleep wake cycle to match the environmental day-night cycle with influence of zeitgebers

Sunlight

• exposure to daylight during the morning hours and early afternoon ADVANCES the sleep–wake cycle

• exposure in the late afternoon and early evening has the opposite effect, delaying the sleep–wake cycle

Light

• sleeping in daylight (or low light) → INTERFERES with NREM-REM sleep cycle

  → can increase duration of NREM stage 1 sleep, less deep sleep + more shallow sleep → frequent arousals + more fragmented sleep

  → explains for shift workers poor sleep

• closing ur eyes dont help → eyelids CANT block sufficient light to supress melatonin production + prevent sleep phase shift

• also flourescent light, tv, phones

Temperature

• core body temperature follows a 24 hour circadian rhythm → linked with sleep-wake cycle → gradually falls during night time and rises during wake phase

• sleep more likely to occur when core body temp decreases → generally 2 hours before falling asleep core body temp decreases

• WARM BATH PRIOR → lowers core body temp cause after u leave shower ur body decreases temp to adapt to cooler environment + promote feelings of relaxation

Eating and drinking patterns

Erratic eating and drinking patterns with highly variable times when meals and snacks are consumed that also VARY from day to day have been found to have DETRIMENTAL effects on the sleep–wake cycle.

→ dont eat right before bed as digestive system follows a circadian rhythm linked to the day-night cycle + digest food during the day but not at night