Chapter 6: Sleep

Question 1

Consciousness

Answer 1

• Awareness of internal / external events: objects, events, sensations, mental experiences and existence
• Referred to as a psychological construct
• Divided into NWC and ASC

Question 2

Normal waking consciousness (NWC)

Ordinary consciousness

Answer 2

• Being awake & aware of internal / external events
• Not considered one single state; always changing
• Includes states of consciousness involving ↑ awareness

Question 3

Altered state of consciousness (ASC)

Answer 3

• Distinctly different from NWC or any waking state in terms of level of awareness and experience
• Involves changes in wakefulness, self / emotional awareness and perceptions of time / place / surroundings
• Normal inhibitions or self-control may weaken
• Can occur naturally or be induced

Question 4

Naturally occurring vs induced ASCs

Answer 4

• Natural – occurs without the need for any aid
  
  • E.g. sleep, dreaming or daydreaming
• Induced – intentionally caused using some kind of aid
  
  • E.g. meditation, hypnosis, intoxication

NOTE: They are not necessarily mutually exclusive. Some naturally occurring states can be induced (e.g. sleep can be induced with sleeping pills that promote drowsiness).

Question 5

Sleep

Answer 5

• ASC that typically occurs naturally & is characterised by partial or total suspension of conscious awareness
• Can be described as a psychological construct
• Made up of REM and NREM sleep

Question 6

Psychological construct

Answer 6

• ‘Constructed’ concept that describes a psychological activity / pattern that cannot be directly observed
• E.g. sleep, consciousness, intelligence, personality
• They are measured indirectly using:
  
  • Info provided by individuals e.g. self reports
  • Demonstrated behaviour e.g. experiment responses
  • Measurable physiological changes e.g. brainwaves

Question 7

Sleep episode vs cycle

Answer 7

• Episode – the full duration of sleep
• Cycle – ~90 minute period during an episode, where we go through stages of REM & NREM sleep, before repeating

Question 8

Measuring consciousness (indicators)

Answer 8

• Physiological; objective (EEG / EMG / EOG)
  
  • Heart rate
  • Body temperature
  • Eye and muscle movements
  • Brainwaves
• Pscyhological; subjective (sleep diaries / vid monitoring)
  
  • Emotional awareness
  • Self control
  • Perceptual and cognitive distortions
  • Time orientation

NOTE: Subjective measures are influenced by personal feelings or opinions whilst objective measures are not.

Question 9

Electroencephalography (EEG)

Objective sleep data

Answer 9

• Studying brain 🧠 wave patterns by detecting, amplifying and recording electrical activity in the brain
• Diff brain waves correlate to diff states of conscioussness

Question 10

EEG limitations

Answer 10

• Poorly measures neural activity that occurs below the cortex (i.e. outer layer of the brain)
• Doesn’t provide detailed info about which particular brain structures are activated + their specific functions

Question 11

Brain waves

Answer 11

• Sponty, rhythmic electrical impulses from brain areas
• Vary in frequency and amplitude

Question 12

Frequency and amplitude of brain waves

Answer 12

• Frequency – number of brain waves per second
  
  • High-freq: faster / more brain waves per second
  • Low-freq: slower / fewer brain waves per second
• Amplitude – intensity of brain waves
  
  • High-amp: larger peaks and troughs
  • Low-amp: smaller peaks and troughs

Question 13

Types of brain waves

Answer 13

• Beta – high freq, low amp
  
  • Present during intensive mental activity during NWC
• Alpha – med freq (↓ than beta), med amp (↑ than beta)
  
  • Common when awake & alert but internally relaxed
  • E.g. sitting down to rest and calmly reflect after completing a mentally stimulating task
  • Possible after a full night of sleep dep
• Theta – med freq (↑ than delta), med amp (↓ than delta)
  
  • Common when drowsy or just before waking
  • Possible when awake & engaged in creative activities
  • Possible after a full night of sleep dep
• Delta – low freq, high amp
  
  • Associated with dreamless sleep / unconsciousness

Question 14

Electromyography (EMG)

Objective sleep data

Answer 14

• Studying electrical activity of muscles 💪 during sleep
• Electrodes attach to skin above the relevant muscles
• ↑ muscular activity & tone = ↑ alertness (and vice versa)

TIP: E(M)G = muscles.

Question 15

EMG limitations

Answer 15

• Can’t distinguish sleepwalking from normal movements
• Can limit movement through (potential) attachment of wires to a machine

Question 16

Electro-oculargraphy (EOG)

Objective sleep data

Answer 16

• Measuring eye 👁 movements / positions during sleep
• Electrodes attach to face areas surrounding the eyes
• Good at distinguishing REM from NREM sleep

TIP: E👁G.

Question 17

Sleep diaries

Subjective sleep data

Answer 17

• A self record of sleep and waking time activities over a period of time (usually one week / more)
• Often used with EEG / EMG to support sleep assessments
• Advantages – non-intrusive, cost effective
• Limitations – subjective, requires compliance

NOTE: Sleep diaries can involve both qualitative and quantitative data (depending on what questions are involved).

Question 18

Video monitoring

Subjective sleep data

Answer 18

• Recording observable responses during sleep which can be linked to different sleep stages / types
• E.g. body position, ‘tossing and turning’ & sleepwalking
• Advantages – natural (no sleep lab), non-intrusive
• Limitation – does not explain the behaviour

NOTE: Sleep lab limitation = artificial environment.

Question 19

Biological rhythms

Answer 19

• Naturally occuring pattern of physiological, psychological or behavioural changes that repeat themselves cyclically
• E.g. menstruation and the sleep–wake cycle
• Divided into circadian and ultradian rhythms

Question 20

Biological clock

Answer 20

• Innate timing that regulates biological rhythms
• Functioning is genetically determined & occurs at a cellular level
• E.g. the suprachiasmatic nucleus (SCN)

Question 21

Circadian rhythm

Answer 21

• Physiological, psychological or behavioural changes that occur as part of a cycle with a duration of ~24 hours
• E.g. the sleep–wake cycle

Question 22

Endogenous vs exogenous

Answer 22

• Endogenous – originating within an organism
  
  • E.g. sleep–wake cycle
• Exogenous – originating outside an organism
  
  • E.g. external cues like light / darkness

Question 23

Ultradian rhythm

Answer 23

• Physiological, psychological or behavioural changes that occur as part of a cycle shorter than 24 hours
• E.g. sleep cycle (~90 min), heartbeat and respiration

Question 24

Factors that indicate that a biological rhythm is a circadian rhythm

Answer 24

• Duration of ~24 hrs that thereby repeats every 24 hrs
• Persists in the absence of external cues
• Can be adjusted (entrained) to match external cues

Question 25

Suprachiasmatic nucleus (SCN)

Answer 25

• Biological clock in the hypothalamus that regulates the timing & activity of the sleep–wake cycle
• Responds to light and communicates with the pineal gland to control melatonin production
• Can operate independently but is also influenced by zeitgebers

NOTE: The SCN, itself, does NOT sense light.

Question 26

Melatonin

Answer 26

• Hormone secreted by pineal gland in hypothalamus
• Influences alertness, drowsiness & sleep-wake cycle
• ↓ light = more melatonin (induces drowsiness & sleep)
• ↑ light = less melatonin (more alert)

NOTE: Artificial light can be bright enough to delay melatonin release.

Question 27

How is melatonin released?

Answer 27

• Light stimulates neurons in the eyes (retina) which send neural messages to the SCN via the optic nerve
• When no / low light is detected, the SCN sends excitatory neural messages to the pineal gland (results in the production and release of melatonin through bloodstream)
• When light is detected, the SCN sends inhibitory messages to the pineal gland (results in suppression of melatonin)

Question 28

Negative feedback loop (melatonin)

Answer 28

• Allows the levels of melatonin in blood to be monitored by SCN

Question 29

Positive and negative impacts of light on the regulation of the SWC

Question 30

Synthetic melatonin

Answer 30

• Used to treat sleep disorders e.g. sleep onset insomnia
• Generally safe for short-term use
• Low likelihood of becoming dependent on its use

Question 31

Hypnogram

Sleep graph

Answer 31

• Shows sleep types & stages in relation to time
• Shows that NREM & REM sleep alternate in a cyclical way

Question 32

Features of a healthy young adult’s sleep that can be seen in a hypnogram

Answer 32

• Alternating sequence of NREM and REM sleep periods
• N3 periods are followed by a climb back to REM
• REM progressively lengthens (dominant in 2nd half)
• Shifting from light to deep sleep after sleep onset
• Cycles last ~90 mins with the correct no. cycles (~4-5)
• More deep sleep in the first half

Question 33

Non-rapid eye movement (NREM) sleep

Answer 33

• Makes up about 75–80% of our total sleep time
• Involves 3 stages (sleep progressively becomes deeper)
• Brain not as active compared to during REM sleep / NWC
• Dominant in the first half of sleep

Question 34

Stages of NREM sleep

Answer 34

• N1 – relatively light sleep (when sleep begins in 1st cycle)
  
  • ↓ 🫀 and 🫁 rate, body temp and muscle tension
  • Slow, rolling 👁 movements, alpha-theta waves
  • Involuntary muscle twitches (hypnic jerks)
  • Low arousal threshold; easy to wake
• N2 – light / moderate sleep (gradually becomes deeper)
  
  • Continued ↓ 🫀 & 🫁 rate, temp, muscle tension
  • 👁 movements stop, theta-delta waves present
  • Slightly ↑ arousal threshold but still easy to wake
  • Brief bursts of electrical activity (sleep spindles)
  • Makes up of most of NREM sleep
• N3 – deep sleep (low wave / delta sleep)
  
  • 🫀 and 🫁 rate slow to their lowest levels
  • Muscles are fully relaxed; we barely move
  • No 👁 movements, delta waves present
  • Highest arousal threshold; difficult to wake
  • Dominant in the first half of sleep

Question 35

Purpose of light / moderate sleep

Answer 35

• About half of a total sleep episode is spent in N2
• Evolutionary purpose for safety
• Allows us to wake in response to potential threats

Question 36

Sleep onset and latency

Answer 36

• Onset – transition period from being awake to asleep
• Latency – amount of time it takes to transition from being awake to being asleep

Question 37

Rapid eye movement (REM) sleep

Paradoxical sleep

Answer 37

• Makes up about 20-25% of our total sleep time
• Involves spontaneous bursts of REM (eyeballs move fast beneath closed eyelids in jerky, coordinated movements)
• Internal bodily functions are more active compared to NREM (i.e. ↑ and more irregular 🫀 and 🫁 rate,↑ BP, etc.)
• Yet, externally, the body appears calm and inactive
• Dominant in the second half of sleep
• Arousal threshold similar to N2 / N3

Question 38

REM vs NREM dreams

Answer 38

• REM
  
  • When most dreaming occurs
  • Tend to follow a narrative structure (realistic/fantasy)
• NREM
  
  • Can be as bizarre as REM dreams
  • Tend to be shorter, less frequent & less structured
  • Less vivid and less likely to be recalled

Question 39

Measuring REM and NREM sleep

Answer 39

• REM Sleep
  
  • EEG – beta-like waves (sawtooth pattern)
  • EOG – high activity (jerky, coordinated movements)
  • EMG – paralysis (no movement)
• NREM Sleep
  
  • EEG – theta-delta waves (diff between N1, N2, N3)
  • EOG – slow, rolling movements / none
  • EMG – some movement

Question 40

Age-related changes in sleep

Answer 40

• Total time spent asleep gradually ↓ as we age
• Proportion of REM sleep ↓ significantly during the first 2 years and then remains relatively stable
• Proportion of NREM sleep ↓ through to old age

Question 41

Why do we sleep?

Answer 41

• Restoration theory – sleep replenishes bodily resources
• REM replenishes the mind, NREM replenishes the body
• Growth hormone released during sleep (aids physical dev)

Question 42

Factors that contribute to inadequate amounts of sleep in adolescence

Answer 42

• Poor sleep habits, hormonal changes, exposure to blue light and busy schedules
• Persistently getting poor quality / insufficient amounts of sleep can result in sleep dept (body & brain functions deteriorate)

Question 43

Sleep onset for newborns and infants

Answer 43

• At birth – sleep onset begins at REM (any time; day/night)
  
  • 50% of sleep is REM and sleep duration is irregular
  • Because the circadian rhythm has yet to fully develop or sync with external cues (i.e. light / dark)
• By 3 months – sleep onset begins at NREM
  
  • Circadian rhythm kicks in
  • Melatonin production becomes more cyclical

Question 44

Why infants need a lot of sleep

Question 45

Differences between the sleep of infants and healthy adults

Answer 45

• Infants sleep for around 12-14 hours a day whereas adults sleep for around 6-7 hours a day
• Infants’ sleep consists of ~50% REM and 50% NREM, whereas an adult would have ~20% REM and 80% NREM
• Infants tend to sleep in multiple blocks of time and wake up frequently, whereas adults generally have one major sleep episode
• Infants’ sleep onset can begin at REM, whereas adults’ sleep onset begins at NREM