sleep P1

What does consciousness mean?

—The awareness of objects and events in the external world and of our own existence and mental experiences at any given moment.

NORMAL WAKING CONSCIOUSNESS (NWC) and ALTERED STATES OF CONSCIOUSNESS (ASC)

NORMAL WAKING CONSCIOUSNESS (NWC)

States of consciousness associated with being awake and aware

of our thoughts and feelings and sensations from the outside

world.

ALTERED STATES OF CONSCIOUSNESS (ASC)

Any state of consciousness that is distinctly different from

NWC, in terms of level of awareness of external events and the

quality of thoughts and feelings that are experienced.

examples

NWC- focused attention, normal wakefulness, listening to teacher, conversation with friend

ASC-unconscious/coma, hypnosis, sleep, daydreaming, meditation, anaesthetised

Types of Altered States

—Naturally Occurring ASC involve physiological and psychological changes that occur automatically and are beyond our conscious control.

◦Examples: Sleep (on the study design!) and Daydreaming

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—Induced ASC involves physiological and psychological changes that have been intentionally produced.

◦Examples: Drug and Alcohol induced ASC (on the study design!), hypnosis, meditation, being anaesthetised.

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Sleep

—Sleep = a regularly and naturally occurring altered state of consciousness that typically occurs spontaneously and is primarily characterised by a loss of conscious awareness. 

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—Two types of sleep:

-NREM

- REM

Non-REM Sleep

—Approx 80% of our sleep time (50% - babies)

—More in first half of the night

—May be when body recovers, repairs, replenishes

—Three distinct stages from light to deepest sleep then back again

REM Sleep

—Period where eyes move rapidly beneath the eye lids

—Internal functioning more active than NREM

—Skeletal muscles relaxed so no movement

—Most dreaming occurs

—May embed memories by strengthening neural connections

—REM periods lengthen and get closer together as the night progresses (mins à hours)

—Infants spend longer in REM than adults (suggests it is required for neurological development.)

—Paradoxical sleep:

◦Internal body and brain active

◦External body relaxed

Summary: REM vs NREM

1) Electromyograph (EMG)

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—Device used to detect, amplify and record the electrical activity of muscles of the body.

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—Used in conjunction with an EEG.

—Detects changes in muscle tone & tension

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—Electrodes are placed over the muscles of the chin (because this area of the body shows the most dramatic changes during sleep).

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2) Electrooculargram (EOG)

—A device used to detect, amplify and record the electrical activity of muscles that control eye movement.

—Uses electrodes attached to the face around the eyes

—Assists in the recognition of REM sleep.

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3. Electroencephalograph (EEG)

—Electroencephalograph = a device used to detect, amplify and record electrical activity in the brain.

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—Electrodes are attached to the surface of the scalp that detect the electrical activity of the neurons in the cerebral cortex.

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—The EEG amplifies and translates the relatively weak electrical activity into a visual pattern of brain waves which are displayed as an electroencephalogram.

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Physiological response – electrical activity of the brain

—D

different types and stages of sleep produce different brain waves,

—Brain waves are measured in frequency and amplitude

—EEGs may be used to identify a particular stage or abnormal brain activity that differs from what would usually be expected.

◦For example, abnormal brain activity during sleep can indicate a sleep disorder, or a particular pattern can determine when a person has fallen asleep

brain waves

Sleep Diaries – Subjective!!

—A self-report method is one where an individual is required to record information that can be used by experts – it is a subjective way to measure state of consciousness.

◦Provide more details of things that cannot be directly observed or measured, such as thoughts and feelings.

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—A Sleep diary or Sleep log is a self-reported record of an individual's sleep and waking time activities, usually over a period of several weeks.

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—Most commonly used in conjunction with polysomnographic tests to support the assessment of sleep disorders.

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—Limitations include accuracy of the information (people often forget to write things down, write incomplete or distorted information or leave things out for fear of embarrassment)

Video Monitoring

—Sleep laboratories usually record externally observable physiological responses on a video camera.

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—Video can later be analysed using frame-by-frame analysis and pictures can be enhanced.

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—Extremely useful in the diagnosis of sleep conditions

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Circadian Rhythm

= biological processes that roughly follow a 24 hour cycle.

◦Circadian is derived from latin – ‘about a day’

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—Are controlled by internal biological processes such as the body temperature cycle

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—Also influenced by external cues that can influence cyclical changes, such as light, external temperature, noise and food

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—In humans, the dominant circadian rhythm is the sleep-wake cycle

◦Periods of time during a day when we naturally feel awake and others when we naturally are inactive, asleep or resting

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Suprachiasmatic nucleus (SCN)

—The suprachiasmatic nucleus (SCN) functions as the master body clock. Found in the hypothalamus.

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—Many cells in the body can independently maintain a 24-hour circadian rhythm but all are ultimately synchronised and controlled by the SCN.

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—At specific times in a 24-hour day, the SCN sends signals to regulate various activities in the body and keep it functioning to a daily schedule of sleep and wakefulness.

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—The SCN can function independently to maintain an approximately 24-hour cycle because of a precise feedback loop of gene expression and inhibition.

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—However, it is influenced by external cues such as exercise, social activity, eating patterns and temperature.

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—The SCN is particularly sensitive to light, and this is why the human circadian rhythm is so closely connected to day and night.

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SCN and Circadian Rhythms

—The SCN regulates the circadian rhythm with the help of light signals from the environment.

—Light-sensitive neurons in the retinas detect incoming light and send messages to the brain’s SCN about the amount of light in the surroundings.

—More light being received by the eyes indicates daytime; less light being received by the eyes indicates night-time.

night

—Night:

◦At night-time when the eyes detect no light, the SCN sends a signal to the pineal gland in the human brain.

◦The pineal gland releases melatonin, a hormone that induces drowsiness.

◦The increased release of melatonin induces sleepiness and decreases cell activity.

◦This process ensures that our sleep is connected to night-time.

day

—Day:

◦During the day when the eyes detect more light, the SCN sends inhibitory messages to the pineal gland

◦Results in the inhibition of melatonin release by the pineal gland. 

◦Less melatonin release by the pineal gland increases cell activity in the body. 

◦The result is that a person does not feel drowsy, and therefore wakefulness is promoted during the day.

—This process allows the circadian rhythm to be synchronised with the outside world and creates a stable cycle that enables you to feel awake during the day and fall asleep at night.

summary of night

—The suprachiasmatic nucleus (SCN)

◦in the hypothalamus

—SCN receives information from the eyes about light levels

—Lack of light stimulates the SCN to trigger the pineal gland to release the hormone melatonin

—Melatonin levels increasing causes us to feel sleepy

summary of day

• The suprachiasmatic nucleus (SCN) in the hypothalamus receives information from the eyes about light levels.

• Increased light levels stimulate the SCN to reduce signals to the pineal gland.

• The pineal gland decreases the release of melatonin.

• Melatonin levels decrease, causing us to feel more alert and awake.

examples

Ultradian Rhythms

= biological rhythms that follow a cycle of less than 24 hours.

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—EG: Sleep cycle is approx. 90 mins

—Attention span and concentration believed to be on 90 minute cycles

The Sleep Cycle

—Progression through NREM sleep cycle from Stage N1 to Stage N3 takes about 45-60 minutes before we move back up through stages 3, 2 and then 1. At this time, we experience REM sleep before starting the cycle again.

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—2, 3, 2, 1, REM……

—INFANTS and certain sleep disorders such as narcolepsy, may start at REM sleep

describe the sleep cycle

Characteristics and Patterns of Sleep 

—Over a typical night we experience two distinct states or types of sleep:

◦1) NREM (non-rapid eye movement sleep)

◦2) REM (rapid eye movement sleep)

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—These occur in a continuous cycle

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—A complete sleep cycle consists of a period of NREM sleep (but not necessarily all four stages) and then a period of REM sleep.

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—A cycle normally lasts 80-120 mins so we go through this cycle approx 4-5 times a night.

Stage 1
NREM Stage 1 (N1)

—Physiological changes – decreased heart rate, breathing, body temp and muscle tension

—Slow eye rolling movements

—Occurs as we drift in and out of true sleep

—When sleep begins in the first sleep cycle

—Overall slowdown of brain wave patters

—Easily awakened

—Gradually lose awareness of surrounds

◦Hypnic jerks occur as the muscles relax

—Lasts 5-10 minutes

◦Sleeper may feel they were never asleep if woken during this stage.

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Stage 2 
NREM Stage 2 (N2)

—Light sleep

—Most people if woken will think they weren’t really asleep but just dozing. 

—HR, breathing, muscle activity and body movement continue to slow

—Body temp continues to drop and eye movement stop 

—Point at which you are truly asleep, 

—Sleep is less easily disturbed than in stage 1

—Lasts 10-20mins

◦Sleep spindles occur = bursts of higher freq. brain waves

◦K complexes occur in response to arousing stimuli. These are bursts of low frequency, higher amplitude waves.  

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Stage 3
NREM Stage 3 (N3)

—Period of deep sleep

—Heart rate and breathing slow to lowest levels

—Muscles are completely relaxed – we barely move

—No eye movements

—Brain waves become slower (largest and slowest – delta waves)

—Less responsive to outside world

—Difficult to wake and are groggy and disorientated

—First sleep cycle can be between 20-40 min in N3 depending on age

—As night progresses less and less time is spent in N3 and may disappear altogether. 

—N3 makes up about 10-15% of total sleep time

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—Progression through the first NREM…

—Progression through the first NREM sleep cycle from N1 to N3 takes about 45-60 mins before gradually moving back up through the lighter sleep of N2 then into the first period of REM sleep.

Changes in sleep through the lifespan

As a person ages through the life span, their need for, and experience of, sleep changes in the following ways:

•The total amount of sleep decreases.

•The proportion of REM sleep decreases significantly from birth until 2 years old.

•The amount of N3 sleep decreases, replaced mostly by N2 sleep.

•A circadian phase delay occurs during adolescence (preference for going to sleep later).

•After adolescence, a shift to a circadian phase advance occurs (preference for going to sleep earlier).

•Awakenings during sleep increase from adulthood to old age.

•Sleep efficiency (the percentage of the time in bed that is spent asleep) reduces

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Outline of circadian rhythm changes across the life span

Main Function of REM Sleep

—‘Brain’

—Help embed memories

—Mental restoration

—Consolidation of learning from that day

—Formation of neural pathways

 

Main Function of NREM Sleep

—‘Body’

—Body recovers, repairs, replenishes

—Physical restoration

—Muscle growth and repair

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REM versus NREM

—Time spent in REM decreases from birth to adolescence then remains relatively stable

◦supports restorative theory – need a lot of REM sleep when young and learning new things to help replenish the mental processes they exhaust during their awake times

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—Newborn – 50% REM

—Child – 20-25% REM

—Adolescent – 20% REM

—Adult – 20% REM

—Elderly – 20% REM

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Total Amount of Sleep

—Amount of time spent sleeping decreases over lifespan

◦Physical growth, tissue repair and recovery from fatigue occurs during NREM.  As we get older and become less active we need less sleep

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—Newborn – 16 hours

—Child – 10-11 hours

—Adolescent – 9 hours

—Adult – 7-8 hours

—Elderly – 6 hours

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