Psychology, Unit 4, SAC 1, 2025 Area of Study 1: How does sleep affect mental processes and behaviour?

NREM sleep

• Makes up approx. 75-80% of total sleep

• Sleep with relatively inactive brain in a body that can move

• Three stages: 1,2,3

• Typically more time is spent in NREM in first half of the night

REM sleep

• Makes up approx. 20-25% of total sleep

• Sleep with active brain in a paralysed body

• Typically more time is spent in REM in second half of the night

• Brain wave pattern associated with REM in like that produced during alert wakefulness

• Body’s internal function is more active than during NREM, e.g. heart rate, breathing

• There is a REM in every cycle

Measurement of physiological responses associated with sleep- Electroencephalograph (EEG)

• Device that detects, amplifies, and records general patterns of electrical activity of the brain
  How it works:

• Each electrode detects and receives signals from many thousands of neurons activated in the vicinity and the EEG averages this out

• Then it amplifies and translates the activity in cortical areas beneath the electrodes into a visual pattern

Frequency

• Number of brain waves per sec

• High frequency= faster and has more brain wave patterns per unit of time

• Low frequency= slower and less brain wave patterns per unit of time

Amplitude

Measures in microvolts and is visually judged by the size of peaks and troughs of the waves

Beta brain wave pattern

• High frequency, low amplitude

• Alertness and intensive mental activity during NWC

• Being awake, attentive and actively thinking

• Present during state of tension, anxiety, threat or fear

Alpha brain wave patterns

• Medium to high frequency, with low amplitude

• Being awake and alert, but mentally and physically relaxed

Theta brain wave patterns

• Medium frequency, low and high amplitude

• Drowsiness

• Falling asleep or just before waking

• Creative, dream like activities

Delta brain wave pattens

• Low frequency, high amplitude

• Unconsciousness

• Deep, dreamless sleep

Electroencephalograph (EEG) strengths and limitations

Strength:

• Provides general info about brain activity in real time without being invasive

• Assists with diagnosis and study of various brain related conditions

Limitations:

• Poorly measures neural activity that occurs below outer layer

• Doesn’t provide detailde info about which particular brain structure is activated

Measurement of physiological responses associated with sleep- Electromyograph(EMG)

• Detects, amplifies and records general patterns of electrical activity of the muscles

• Data is obtained by attaching electrodes to the skin above the relevant muscles

Measurement of physiological responses associated with sleep- Electro-oculargraph(EOG)

Detects, amplifies and records electrical activity of the eye muscles

Subject reporting of consciousness- self report

Participant’s written or spoken responses to questions, statements or instructions presented by the researcher

Subject reporting of consciousness- sleep diary

Self reported record of an individual’s sleep and waking time

Subject reporting of consciousness- video monitoring

Records externally observable physiological responses, including behaviour

Biological clock

Innate timing mechanism that regulates the cycle of a biological rhythm

Circadian rhythm

• Biological process that follows a 24hr cycle

• Controlled by internal body clock

• Circadian clock is found in the hypothalamus, called the SCN

Ultradian ryhthm

• Biological rhythm that follows a cycle less than 24hrs, e.g. blinking, sleep patterns

• We generally experience 4 to 5, 90 min cycles of REM and NREM

Suprachiasmatic nucleus (SCN)

• The brain's primary circadian clock, located above the optic nerve. - Responds to light cues by regulating melatonin production by sending neuronal messages to the pineal gland. - Synchronises the sleep-wake cycle with the 24-hour day, promoting alertness during light and sleepiness during dark.

Melatonin

• Hormone associated with alertness

• High levels=drowsiness

• Low levels=more alert

• Less light(sunset/dusk)=more melatonin secreted

• More light(sunrise/morning)=less melatonin secreted

Sleep onset

Transition period from being awake to being asleep

Sleep latency

Length of time taken to transition from being awake to asleep

NREM stage 1(N1)

• 5% of total sleep time

• Beginning of sleep

• Low arousal threshold, if woken during this time it may feel like you haven’t slept at all

• Decreased heart+breathing rate, body temp, eye movements and muscle tension

• Brain waves slow from wakeful daytime patterns

NREM stage 2(N2)

• 45-55% of total sleep time

• Higher arousal threshold(requires more intense stimuli to wake that N1)

• Period of light sleep that becomes deeper

• Slowed heart+breathing rate, muscle activity and body movement

• Body temp continues to fall and eye movements stop

• Brain waves slow further and is marked by sleep spindles(burst of electrical activity) signalling transition to N2

• In first cycle it lasts for 10-15 mins and lengthens in each succesive cycle

NREM stage 3(N3)

• 10-15% of total sleep time

• Highest arousal threshold

• Deep sleep

• Heart+breathing rate at lowest levels

• Muscles completely relaxed, minimal movements

• No eye movements

• Brain waves are slower with delta brain waves present 50% of the time

• When woken, sleep inertia is experiences(groggy, disoriented, poor memory of sleep events)

• In first sleep cycle, person may spend 20-20mins in N3 and as night progresses less and less time is spent in it until it disappears all together

Sleep in newborns(0-3 months old)

• Amount of sleep required= 16 hours

• Time spent in NREM= 50%

• Time spent in REM= 50%

• sleep onset can occur at any time of day or night with no regular rhythm

• one episode can last from 30 minutes to 3 or 4 hours.

• Sleep onset can also occur in REM sleep, not NREM Stage 1, and each sleep cycle is only 1 or 2 cycles due to the shorter sleep episodes.

Sleep in infants(3 months-2 years)

• Amount of sleep needed=14-16hrs

• Time spent in NREM= 50%

• Time spent in REM= 50%

• NREM-REM sleep cycles are more regular. Sleep onset begins with NREM Stage 1, REM sleep decreases and the total sleep cycles are about 50-60 minutes

• By six months of age, total sleep time reduces slightly and the longest continuous sleep episode lengths to 5 to 8 hours of sleep. A full NREM sleep cycle is likely to be occurring, and the muscle paralysis of REM has set in. This is attributed to maturation of the brain and biological mechanisms controlling the sleep wake cycle

Children(2-12 years)

• Sleep requires=10-11hrs

• Proportion spent in NREM=75-80%

• Proportion spent in REM=20-25%

• The proportion of REM sleep continues to decrease and NREM sleep increases, with a greater proportion spent in stages 2 and 3. About 50% of NREM sleep is spent in NREM Stage 3, and this decreases markedly from about age 10.

• Children up to mid adolescence may often ‘skip’ their first REM sleep period, due to the quantity and intensity of their delta brain wave sleep early in the sleep episode

Adolescent(12-18years)

• Sleep required=9 hours

• Proportion spent in NREM=80%

• Proportion spent in REM=20%

• By mid-adolescence, the first REM period is unlikely to be skipped, and a sleep episode represents that of a young adult

• Within NREM sleep, the amount of stage 3 deep sleep progressively declines, and the time spent in N2 increases.

Adults(18-60 years)

• Sleep required=7-8 hours

• Proportion spent in NREM=80%

• Proportion spent in REM=20%

• The overall pattern of sleep shows a progressive decline in the duration of a typical sleep episode, and in the proportions of time spent in REM and NREM sleep, and there is a gradual loss of N3 sleep.

• As an individual ages, deep sleep declines at about 2% per decade. People aged 60 may spend only half as much time in N3 as they did at age 20. Eventually N3 disappears altogether, particularly in males

Elderly(60+ years)

• Sleep required=6-7 hours

• Proportion in NREM= 80%

• Proportion in REM=20%

• Older people tend to become sleepier in the early evening and wake earlier in the morning compared to younger adults.

• Rarely experience NREM stage 3- majority of sleep is in NREM stage 1 and 2

Partial sleep deprivation

Less than required amount of sleep (or poor quality sleep) within 24 hour periodless than required amount of sleep (or poor quality sleep) within 24 hour period

Affective impacts of sleep deprivation

-Quicker and more intense or exaggerated emotional responses

-Eg. snapping at others, emotional outbursts, less empathy, overact to small events, more aggressive impulses.

Behavioural impacts of sleep deprivation

-Physical changes– yawning, rubbing eyes, shaking hands

-Increased risk takin

-Reduced motor and hand-eye coordination

-Eating more

-Can also experience microsleeps – a brief period of sleep

(1-10 seconds) in which the person typically has eyes open

but a fixed gaze and doesn’t blink.

Cognitive impacts of sleep deprivation

-Lapses in attention (selective and divided)

-Poorer decision making and problem solving ability

-Impaired learning and memory ability

-Difficulty completing automatic processes (but less impairment on controlled processes)

-Illogical or irrational thinking

Similarities between the ways a 0.10 BAC and full sleep deprivation impacts cognition

•Reduced speed and accuracy performing tasks

•Slower mental processes

•Decreased ability to reason and problem solve

•Greater difficulty making sense of the world

•Reduced ability to make decisions quickly and effectively

•Cognitive distortion

Similarities between affecttive impacts of a 0.10 BAC and full sleep deprivation

-Sleep deprivation can make someone irritable or sensitive

-0.10 BAC can make someone more happy and excited or more angry and sad

Circadian phase disorders

-sleep disorders involving sleep disruption that is primarily due to a mismatch between an individual’s sleep–wake pattern and the pattern that is desired or required by the external environment (night-day cycle).

Delayed sleep phase syndrome (DSPS)

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

-natural tendency to wake up later than what is normal according to ‘society’s clock’.

-Onset of the sleep wake cycle is significantly delayed, often by 2 to 3 hours and in some cases much longer

•Three prominent symptoms for people with DSPS are:

•Sleep onset insomnia

•Difficulty waking up at the desired or necessary time

•Excessive sleepiness

Delayed sleep phase syndrome (DSPS) impact on functioning

•may lead to a mismatch between their school or work start time and therefore require waking earlier than would otherwise occur naturally. This can then lead to sleepiness throughout the day and other effects of sleep deprivation.

Treatment of DSPS

light therapy-increasing exposure to bright light shortly after waking up and reducing light exposure in the evening, particularly before bedtime, melatonin supplements

Advanced sleep phase disorder (ASPD)

-a persistent disturbance of the sleep wake cycle characterized by advance of the major sleep episode to an earlier time compared to desired or conventional sleep times(sleeping and waking up too early)

-Typical sleep onset times are between 6pm and 8pm, and wake times are between 1am and 3am

Advanced sleep phase disorder (ASPD)impact on functioning

•persistent sleep deprivation and daytime sleepiness.

-They then experience significant distress and/or impairments in important areas of everyday life.

Advanced sleep phase disorder (ASPD) treatments

melatonin and bright light visual stimulation

Shift work disorders

•employment that is outside the period of a normal working day and may follow a different pattern in consecutive periods of the week.

Impacts of shiftwork

-conflicts with our natural body clock, forcing people to be awake when they should be sleeping.

-Difficulty falling asleep (delayed sleep onset) during the day due to environmental factors

-less total hours slept

Reducing the effects of shift work

-a fixed schedule that requires employees to work the same shift on a regular, ongoing basis is best to reduce effects of shift work.

Sleep hygiene

changing basic lifestyle habits that influence sleep onset, good quality sleep and alertness during the normal waking period.

Sleep hygiene practices

•Establish a regular relaxing sleep schedule and bedtime routine

•Associate your bed and bedroom with sleep

•Avoid activities that are stimulating in the hour before bed

•When you cannot sleep, get up

•Avoid napping during the normal waking period

•Avoid stimulants such as caffeine, nicotine and alcohol too close to bedtime

•Exercise to promote good sleep

•Food can be disruptive just before bed

•Improve your sleeping environment

-Ensure adequate exposure to natural light

Zietgebers

-environmental time cues.

-Types of zietgebers: daylight, blue light, eating and drinking patterns, temperature and anything else that can signal time.

Zeitgebers in the external environment are used by the SCN to adjust circadian rhythms to a 24 hour day

Daylight as a zeitgeber

Exposure to daylight during morning and early afternoon hours advances the sleep wake cycle, pushing it forward. Daylight in the late afternoon and early evening delays the sleep wake cycle,pushing it back to a later time

-Daylight can shift the sleep wake cycle

Blue light as a zeitgeber

helps keep us alert by suppressing the secretion of melatonin.

Too much exposure to blue light in the evening disrupts our circadian rhythms leaving us feeling alert instead of drowsy and ready for sleep.

-It reduces or delays the natural production of melatonin and decreases feelings of sleepiness.

-Can cause a phase shift resulting in delayed sleep syndrome

Temperature zeitgeber

•Sleep is most likely to occur when core body temperature decreases, and much less likely to occur during the rises when the body is preparing for wakefulness.

•Generally, about two hours before falling asleep, our core body temperature starts to decrease under circadian control, coinciding with the secretion of melatonin.

Air temperature can be used as a zeitgeber to signal and help get the body ready for sleep

•a room temperature of around 18 degrees is best for sleep but there is no ideal sleep temperature that would suit everyone.

•Ensuring your bedroom is not too hot or too cold may help with regulating your core temperature and signal your body that its time for bed and sleep.

Eating and drinking patterns as a zeitgeber

•The eating and drinking pattern then has to be maintained in a stable manner. Erratic patterns can be detrimental on the sleep wake cycle.

•Food can be disruptive just before sleep as our digestive system also follows a circadian rhythm linked to the day night cycle. It is ready to digest food during the day, but not at night. So it is important not be hungry or full at bedtime as this makes it difficult to fall asleep.