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Brain highly active during sleep and

Efforts physical and mental health


Ironically sex and eating are our biggest motivators but we spend the most time of our life



Sleep is actually a

Behaviour. Not just an action or a resting period.


Electrophysiological Measurement of Sleep

§ Sleep research is conducted in a sleep laboratory.
§ Electrodes are attached to the subjects scalp to record electrical activity of the brain. The amplifier records an electroencephalogram (EEG).
§ Electrodes are also attached to the subjects chin to record muscle activity recorded as an electromyogram (EMG).
§ Electrodes placed around the eyes monitor eye movements recorded as an electro - oculogram (EOG).


Brain activity when we’re are awake and at rest

When we are awake, our EEG shows two basic patterns:
Alpha activity consists of regular, medium frequency waves (8-12 Hz).
Beta activity is generally associated wave forms that are irregular at an amplitude of 13-30 Hz.
Beta activity is desynchronous; it’s a reflection of different neural circuits actively processing information at the same time.


Stage 1 of Sleep

When we get drowsy, we show theta activity (3.5-7.5 Hz). This is the transition between wakefulness and sleep.
Muscle activity slows down


Stage 2 of Sleep

After about 10 minutes, the EEG becomes irregular with mixture of theta activity, sleep spindles and K complexes.
- Sleep spindles are short bursts of waves (12-14 Hz) which occur between 2-5 times a minute during sleep stages 1-4.
- Older people show more K complexes. K complexes are sudden, sharp waveforms. They are found during stage 2 only. They occur spontaneously at approximately 1 per minute and can be triggered by unexpected noise.

Both seem to keep ppl asleep.
Older ppl fewer sleep spindles, but more k complexes.

If woken up, during this stage, feel grooggy.
Breathing slows and body temp decreases a little.


Stages 3 and 4 of Sleep
aka slow wave sleep.

Stages 3 and 4 are characterised by high-amplitude delta waves (less that 3.5 Hz). They occur more frequently in stage 4 (deep sleep).
More delta activity in stage 4.
During decent of waveform as sleeping, inhibitory. Biphasic


REM Sleep

Finally, about 90 minutes after the beginning of sleep, we enter REM sleep characterised by Rapid Eye Movements.
The activity in REM sleep is desynchronised, sprinkled with theta and beta activity.
The EMG becomes silent (no muscle tone). Infact, apart from occasional twitching, muscles are totally inactive during REM sleep.


Sleep Patterns

§ Stages 1-4 are referred to as non-REM sleep.
§ Stages 3-4 are referred to as slow-wave sleep because of slow, high
amplitude delta waves.
§ At stage 4 you’re usually in deep sleep. Can’t be awakened by noise.if awoken are confused, irritated and grumpy.
Cerebral blood flow and oxygen consumption decrease.
§ During REM you don’t react to noise but you can be aroused by meaningful stimuli. Like name. Wake up alert and aroused.
§ Dreaming occurs during REM sleep. Cerebral blood flow and oxygen consumption increase. In REM sleep, muscles are inactive.
Wet dreams and orgasm possible. Absence of sexual arousal.


90-minute sleep state

Sleep alternates between REM and non-REM patterns of sleep.
§ Each sleep cycle is about 90 minutes long (20-30 minutes of REM sleep). 2.5-3h during 8h cycle.

Amount of rem sleep increases as night goes on.


Mental Activity During Sleep

§ People who report their dreams are ‘conscious’ during sleep.
§ There is high cerebral blood flow to the visual association cortex which may account for the visual hallucinations that occur during dreams.
§ There is low blood flow to the primary visual cortex (because the retina is not receiving any light) and the prefrontal cortex (which makes dreams temporally disorganised).
“... the dreamer often has no feeling of striving for long-term goals but rather is carried along by the flow of time by circumstances that crop up in an unpredictable way.”
All ppl dream, few ppl remember them. Unless awoken during rem.
All have visual hallucination,


Comparative Analysis of Sleep

When lions have gorged themselves on a kill, they may sleep continuously for three days!
In bottle nosed dolphins, the two hemispheres sleep independently so they remain behaviourally alert.
see cute lion sleep on back Photo. ^o^


Only birds and mammals exhibit rem sleep.

Sleep is universal though.
Obviously flamingo leg does not go limp.
Sleep dependant, on vulnerability to predator attack. And how much they need to eat to survive.


Functions of Slow-Wave Sleep (I)
Note cannot defy urge to sleep.
§ Effects of sleep deprivation: human studies

- Lack of sleep affects cognitive abilities rather than physical abilities. Does not seem to be to rest physically that we sleep. Really for brain.
- You never regain lost sleep after sleep deprivation.
Though it appears you make up a bit more of stage 4 and REM sleep and brain will try to accomplish this. Compared to stages 1-2. Like 50% vs 7%. Anecdote of boy who stayed up for 1 consecutive days.

- Presence of delta activity and low levels of physiological activity (i.e. low cerebral metabolic rate and cerebral blood flow) during slow-wave sleep indicates that the brain is resting.

- The brain must restore the effects of oxidative stress. Free radical, highgly reactive oxygen species atoms. O2
-Damages cells! Free radicals and antioxidants.


Effects of sleep deprivation: animal studies

Yoke control rat. Vs experimental rat.
Both rats received equal amounts of exercise but only one animal was sleep deprived (the experimental rat).
A computer recorded EEG of both rats. If EEG of ‘experimental rat’ indicated that it was falling asleep, the motor was activated forcing both animals to exercise.
Experimental rat reduced its total sleep by 87%. The yoked rat reduced its total sleep by 31%.


- A yoked-control procedure is when

both animals receive the same amount of treatment at the ‘same’ time.


Functions of REM Sleep

§ Highest proportion of REM sleep is seen during the active phases of development: approximately 70% of a newborn infants sleep is REM sleep. In adulthood, only 15% of sleep is dedicated to REM sleep.
§ Consolidates memories of events of previous day.
§ In rats, REM sleep facilitates learning. Esp. Emotional events.
Increase in running speed
Increase in REM sleep
Once the task is well learned, REM sleep declines back to baseline levels. If sleep deprived, performance of learned tasks suffers

May relate to amount of memory you have for next day to learn more...? Depends previous night rem/day learning.


Sleep Disorders: Insomnia

§ Insomnia can only be defined in relation to a person’s particular need for sleep.
§ Insomnia is a symptom characterized by persistent difficulty falling asleep or staying asleep despite the opportunity.
§ Causes of insomnia:
- Psychoactive drugs or stimulants (e.g. caffeine,
amphetamine, cocaine, herbs).
- Hormonal shifts (e.g. preceding menstruation and during
- Psychological problems (e.g. fear, stress, anxiety)
- Changes in circadian rhythms (e.g. Shift work, jet lag
- Abuse of sleeping medications produce drug-dependency
insomnia. Newer drugs though leave you refreshed, focus on day after now esp. Imp.


Sleep Disorders: Sleep Apnea

§ Sleep apnea is insomnia caused by the inability to sleep
and breath at the same time.
§ During a period of sleep apnea:
- the level of carbon dioxide in the blood stimulates
chemoreceptors (i.e. chemical receptors).
- The person wakes up gasping for air.
- The oxygen level in the blood normalises and the cycle
begins again.
§ Often sleep apnea is caused by an obstruction of the airway.
All get this some of the time, stimulate receptors, gasp for air.


Sleep Disorders: Narcolepsy

§ Narcolepsy is a neurological disorder characterised by
sleep at inappropriate times.
§ Symptoms: there are a variety but here are a few.
- ‘Sleep attack’ is an overwhelming urge to sleep. Happens regularly.

- Cataplexy is when a person suddenly wilts and falls down. It is precipitated by strong emotional reactions or sudden physical effort (e.g. laughter, anger, excitability).

Aside on power nap, afternoon dips due to big lunch and siestas in oh' europe


Narcolepsy is a Genetic Disorder

§ Narcolepsy is caused by a mutation of a gene that produces a receptor for the peptide neurotransmitter hypocretin 2 (Lin et al., 1999).
§ Mice with a genetic mutation that caused the eventual death of hypocretinergic neurons show symptoms of narcolepsy as adults (Hara et al., 2001).
§ Patients with narcolepsy are born with hypocretinergic neurons but the immune system attacks these neurons usually during adolescence.
§ The same genetic mutation causes narcolepsy in dogs.


REM Sleep Behaviour Disorder

§ People with REM sleep behaviour disorder act out their dreams.
§ Symptoms of REM sleep behaviour disorder are the opposite of cataplexy; instead of exhibiting paralysis during REM sleep, they DO NOT exhibit paralysis during REM sleep.


Problems with Slow-Wave Sleep

In stage 4, behaviours may include bedwetting (nocturnal enuresis), sleepwalking (somnambulism) and night terrors (pavor nocturnus).
§ Night terrors consist of anguished screams, trembling, rapid pulse and often no memory of what caused the terror.


Sleep paralysis is caused by REM sleep that

intrudes during waking hours. The person is unable to move just before the onset of sleep and upon waking in the morning. May show hypnagogic hallucinations.