U4A1 - How Does Sleep Affect Mental Processes and Behavior

sleep

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

how is sleep is a psychological construct

• constructs are ways to describe the patterns of our experiences

• based on scientifically verifiable measurable events or processes or inferred from scientifically collected data when not directly observable

• because its fundamentally private in nature to an individual, we can only infer sleep based on observable and physiological responses associated with sleep

biological rhythms

• set patterns of periods physiological change(s)

• controlled by biological clocks that are contained in almost every tissue and organ in almost every tissue and organ

• master clock in brain coordinates activity

circadian rhythms

• 24 hours

• endogenous, originates within each individual

• allows internal body clock to sync with external time cues (environment)

• sleep wake cycle can be shifted and aligned to new cues like body temp and hormones like cortisol and melatonin

ultradian rhythms

• shorter than 24

• biological processes that follow an ultradian rhythm are breathing, heart rate, hormone secretion, hunger, activity levels

• sleep in a 90 minute cycle, more than one a day, with rem and nrem combined

levels of consciousness

• sustained attention

• normal wakefulness

• daydreaming

• meditative state

• hypnotised

• asleep

• anesthetised

• coma

normal waking consciousness

• ordinary consciousness is being awake and aware

• having internal thoughts, feelings, reactions

altered state of consciousness can be caused by

• induced through alcohol, hypnosis, meditation, anesthesia

• naturally occurring like sleep or daydreaming

• aren’t necessarily mutually exclusive, meaning some can fit in both categories

altered state of consciousness

• sleep is an ASC with reduced metabolism and lowered consciousness

• during an ASC wakefulness, self awareness, emotional awareness and perceptions of time, place and surroundings may change

qualitative measures

sleep diaries, video monitoring

sleep diaries

• self monitoring of relevant data (self report)

• time trying to fall asleep, length and number of wakings, how rested individuals feel, sleepiness during day, diet/exercise

video monitoring

• use of cameras to record externally observable physiological responses through sleep (observational study)

• changes in posture, tossing and turning, breathing, sleep walking and talking

what can changes in posture indicate

can indicate that individuals have gone back to earlier stages of sleep and then gone back to REM

why is video monitoring important

brain patterns when in REM are the same as when we’re awake which

quantitative measures

• detects, amplifies and records electrical activity of

• tells us what stage of sleep someone is in and whether they’re asleep or not

• electroencephalography, electromyography, electro-oculography

electroencephalography (EEG)

• the brain wave patterns

• measures frequency of brain waves

frequency

speed as shown by number of waves per second

amplitude

intensity as shown by the size of peaks and troughs of waves

electromyography (EMG)

• body muscles

• mostly used to show muscle activity (movement) and muscle tone (tension)

• always lower muscle tension in deeper stages of sleep

electro-oculography (EOG)

• the muscles that move the eyes

• commonly used to show eye movements or eye postitions

• used for distinctions between REM and NREM

REM details

• dreaming stage, most vivid memorable dreams that are narrative and abstract

• high frequency, low amplitude

• spontaneous bursts of rapid eye movement

• similar brain activity to wakefulness

• where learning and memory happens, allowing LTP and LTD and to be consolidated

• lower muscle movement to stop you from jumping up in your dreams

NREM1

• sleep initiation, transitional stage, light sleep

• less frequency, higher amplitude

• lowered level of bodily arousal with decreased heart rate, breathing, muscle tension, temp, slow rolling eye movements

• hypnic jerks, involuntary muscle twitches

• low arousal threshold

NREM2

• even less frequency and higher amplitude than 1

• light to moderate sleep

• continued decrease in arousal however eye movements stop

• bursts of electrical activity help resist being woken up by environmental stimuli like noises

NREM

type of sleep characterised by a progressive decline in physiological activity

REM

a type of sleep characterised by quick darting of the eyes behind closed eyelids and an increase in physiological activity

NREM3

• even less frequency and higher amplitude

• restoration of muscles, muscle development and muscle growth which is why when you’re young you spend so much time in 3

• deep, dreamless sleep

• highest arousal threshold, mental lag if woken

• lowest levels of heart rate and breathing

newborn

• 0-3 months

• 14-17 hours 50/50

• highest sleep duration of entire lifespan for rapid growth

• REM sleep boosts brain growth, development and consolidates learning and memory

• muscle twitches in REM may help develop sensorimotor system and coordinating sensory experiences like seeing, hearing, touching

• irregular sleep duration until circadian rhythms sleep at 2-3 months

infant

• 4-11 months

• 12-16 hours

• 40/60

• infants begin sleeping for longer periods at a time as circadian rhythm develops a more regular sleep pattern following the day night cycle

toddler

• 1-2 years

• 11-14 hours

• 30/70

• proportion of REM sleep has had its greatest decline and only decreases small amount over rest of lifespan

preschooler

• 3-5 years

• 10-13 hours

• 25/75

• timing of circadian rhythms may advance and sleep shifts to earlier in the evening as children begin to drop daytime naps

school aged children

• 6-13 years

• 9-11 hours

• 20/80

• specifically nrem 3 increases because a lot of development occurs in this age

• timing of circadian rhythm gradually delays and sleep shifts to alter in evening

adolescence

• 14-17 years

• 8-10 hours

• 20/80

• decreased 3, increased 2

• timing of sleep changed because of delayed release of melatonin 1-2 hours later

young adult

• 18-25 years

• 7-9 hours

• 20/80

• circadian phase advance begins towards end of stage resulting in preference for earlier sleep time

• melatonin concentration begins to decline after puberty

• continued decrease in nrem3

adult

• 25-64 years

• 7-9 hours

• 20/80

• later in stage n3 declines and is replaced

• melatonin concentrations continue to decline

older adult

• 65+ years

• 7-8 hours

• 18/82

• shallow sleep and more awakenings, sleep latency

• circadian phase advance occurs and less sleep may be achieved if person resists body’s preference for earlier bedtime and earlier awakening

• amount of n3 sleep continues to decline or may not occur at all replaced by n2

• melatonin concentrations continue to decline

sleep deprivation

state caused by inadequate quantity or quality of sleep, voluntary or involuntary

total sleep deprivation

• involves not having sleep at all over a short term or long term

• more than 24 hours

partial sleep deprivation

• involves having less sleep either quantity or quality than what is normally required

• can occur periodically or persistently over a short or long term

• effects tend to be minor and temporary

• accumulation of sleep debt

• between 17-24 hours

affective functinoing

• interfere with emotional regulation and reactivity, more likely with REM deprivation

• amplified emotional responses

• harder to accurately judge others emotions and reactions

• radical emotional empathy

• easily irritated, frustrated and aggressive, harder to control impulses

behavioral functioning

• microsleep

• sleep inertia

• slower reaction times

• excessive sleepiness when awake

• fatigue and drowsiness

• difficulty in maintaining focus and concentration

micorosleep

sleep episode that lasts for a few seconds

sleep inertia

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

cognitive functinoing

• performing tasks, how we think, being able to think clearly and solving problems

• impaired cognitive funcitnoing

• reduced ability to divide attention

• reduced ability to think clearly

• likely to think irrationally

• difficulties decision making and creative thinking

• impaired info processing, memory and learning

• overlooking details

sleep depravation and BAC

• a higher a person’s BAC the more their cognition, concentration, and mood might be impaired or damaged

• 17 0.05%

• 24 0.1%

suprachiasmatic nucleus

areas of the brain’s hypothalamus that is the master of biological clocks

scn roles

• regulates timing and activity of circadian sleep wake cycle

• responds to light (located above optic nerves) to control production of melatonin

• sends neuronal messages to nearby pineal gland which secretes melatonin

• increases body temp, releases cortisol to promote alertness and arousal during day

melatonin

• hormone responsible for sleep initiation and regulation of sleep-wake cycle

• produced by pineal glands into bloodstream, higher amount in blood associated with greater drowsiness

• facilitates transition to sleep and promotes consistent quality rest

• affected by artificial light

why do melatonin levels decrease with age

• natural wear and tear of biological clock and changes within brain

• pineal gland calcification, accumlates calcium deposits reducing functional capacity

circadian rhythm sleep disorders

sleep disorders involving sleep disturbance that is primarily due to mismatch between an individual’s sleep wake patterns, circadian rhythms and the pattern that is desired

sleep disorders may be due to

• natural malfunction in biological mechanisms

• external environment

• social schedule

delayed sleep phase syndrome

major sleep episode is delayed in relation to desired/conventional time

• related to sleep onset insomnia, difficulties falling asleep

• difficulties wakening, excessive sleepiness in day

• mismatches with time cues in environment

• worsens in adolescence and early adulthood

shift work disorder

results from work shifts in regular sleep periods

• causes insomnia and excessive sleepiness during work

• reduction in total sleep time and higher frequency of sleep disturbance due to rotating shift from day to night

• moving shift forward is better than backwards

• police, paramedics, fire fighters, doctors, nurses

advanced sleep phase disorder

• persistent disturbance due to timing of major sleep episode occurring earlier than desired

• rare disorder more common in older people

• early morning insomnia

• persistent sleep deprivation and daytime sleepiness

• may be due to deterioration of body clock

bright light therapy

provides timed exposure of the eyes to intense but safe amounts of light ensuring you feel awake at specific times and sleepy at specific times

bright light therapy aim, details

• aims to shift sleep wake cycles to desired schedule

• lamps, visors, light box commonly used

• light is brighter than indoor light but not as direct as sunlight

• therapy is gradual for eg 45 mins a day

effects of bright light therapy

• influences melatonin secretion from pineal gland

• no major side effects only minor like dry skin, headache, eye irritation

shifting the cycle

forward is sleepy earlier, backward is sleepy later

delayed sleep phase syndrome blt

• waking time later in morning

• light exposure during early morning hours like 6-8am ensuring when you wake you feel alert, energised and melatonin is inhibited

• forward

advance sleep phase disorder blt

• waking up earlier than desired

• light exposure early in the evening 7-8pm or whenever they start to feel tired present light

• backwards

shift work sleep disorder blt

• tries to sleep at times the body expects to be awake

• avoid daylight between shifts like wearing sunglasses

• using light treatment in evening and before shift can help individuals with regular working nights by inhibiting melatonin secretion

variables to consider in blt

• right time of day

• right intensity of light

• right amount of time

how to know the right time of day in blt

• how close individual is exposed to light to optimal time determined by core body temperature

• early morning, early evening, before a shift

zeitgebers

environmental time cues that are used by the scn to adjust circadian rhythms so that they are synchronised and aligned with the 24 hour day night cycle of our external environment

daylight - source, how it may be used, why it would work

• sunlight

• seek exposure during day, gradually reduce exposure from later afternoon/early evening prior to bed time

• timing of light exposure will promote or supress melatonin secretion, sleep is more likely to occur when melatonin levels rise

blue light

• sunlight, electronics

• seek exposure during day, gradually reduce exposure from later afternoon and early evening prior to bedtime

• timing of light exposure will promote or suppress melatonin secretion, sleep is more likely to occur when melatonin levels rises

temperature

• atmosphere

• adjust temperature to match with natural circadian drop in core body temp in the evening, you should go to sleep cold

• sleep is more likely to occur when core body temp decreases in the evening aligned with other environmental and circadian changes like darkness and increased melatonin level

eating and drinking patterns

• meal, snacks, drinks

• maintain routine meal and drink times in sync with desired cycle, avoid erratic cycle, avoid eating or drinking close to bed

• sleep is more likely to occur when eating, drinking, sleep patterns and the environmental day night pattern and other zeitgebers are aligned

why shouldn’t you eat or drink close to bedtime

because digestion system is active and working which can make it difficult to fall asleep

good hygiene practices for sleep

• establish a regular relaxing sleep schedule with bedtime routine

• associate bed and bedroom with sleep

• avoid stimulants like caffeine, nicotine and alcohol close to bedti