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)
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 <50% Delta waves occur
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)
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