body and behaviour - task 6

• hypothalamus
• pineal gland
• reticular formation
• suprachiasmic nucleus (SCN)

• stage 1
• stage 2
• stage 3

• insomnia
• hyperinsomnia
• REM sleep-related disorders

- occur both during REM and NREM stages

- often incorporate external stimuli

- involve physical sexual arousal (even when the dream has no sexual content)

- long periods of wakefulness cause physiological and behavioural disturbances

- as deprivation continues, these disturbances get worse and worse

- after the end of deprivation, much of the sleep lost is regained

- all disorders of initiating and maintaining sleep

- associated with many psychiatric disorders

- causes: iatrogenic (caused by wrongfully prescribed sleeping pills and the tolerance built up for them), sleep apnea (person stops breathing several times during the night and that wakes them up, can be either obstructive apnea or central sleep apnea), periodic limb movement disorder (twitches), restless leg syndrome

- treatment: sleep restriction therapy

- all disorders of excessive sleep or excessive sleepiness

- associated with many psychiatric disorders

- types:

• narcolepsy
• cataplexy

- narcolepsy can be also classified here

- REM-sleep behaviour disorder- REM sleep without muscle atonia, so a person physically acts out thier dreams

- being awake disrupts homeostasis and sleep restores it (by restoring energy levels, detoxifying the brain and other organs/tissues, restoring synaptic plasticity)

- humans had to adapt their internal clock to the day and night cycle

- sleep as conservation of energy and as prevention from being hunted

- a 24 hour cycle

- it synchronizes the body with external cues (day and night)

- almost all physiological measures (e.g. wakefulness and sleep, hormone levels, body temperature, drug sensitivity) change in a regular fashion during the circadian rhythm

• infradian- shorter than a day
• ultradian- longer than a day

• anterior hypothalamus (basal forebrain area)- sleep
• posterior hypothalamus (midbrain area)- wakefulness

- secretes melatonin

- reticular activation system:

• low levels of activity- sleep
• high levels of activity- wakefulness

- caudal reticular formation- REM sleep controlled by a variety of nuclei scattered here, each site is responsible for controlling one of the major indices of REM sleep: reduction of core muscle tone, EEG desynchronization, rapid eye movements, etc., REM occurs only when a network of different structures becomes active together

- subregion of the thalamus above the optic chiasm, place where the optic tracts leave the optic chiasm- retinohypothalamic tracts

- controls the circadian rhythm- SNC neurons are inactive at night and fire during the day

- retinal ganglion cells send their axons along the retinohypothalamic pathway splitting off at the optic chiasm to synapse directly in the SNC- this pathway carries information about light to the hypothalamus

- retinal ganglion cells- light-sensitive, depend on their special photopigment melanopsin (not on rods and cones), it’s the most sensitive to blue light

- low-voltage, high frequency

- alpha waves- just before going to sleep

- 2 substages:

• initial stage 1- NREM1- the first cycle of stage 1, not marked by any striking EMG or EOG differences from wakefulness
• emergent stage 1- REM- accompaniedby REM sleep

- voltage increasing and frequency decreasing

- K-complex waves- single large pnegative waves followed by a single large positive wave, triggered by noise

- sleep spindles- bursts of coherent activity

- high voltage and low frequency- slow wave sleep

- deep, hard to wake up from

- delta waves- high voltage and low frequency, synchronization of cortical activity

1. Hobson's activation-synthesis hypothesis

2. Hobson's protoconsciousness theory

3. Revonsuo's evolutionary theory

during sleep many brainstem neural circuits become active and flood the cerebral cortex with random neural signals- the cortex tries to make sense of these signals and synthesise them into a whole bigger picture, so it creates a storyline

dreams as training virtual prototypes of our conscious experiences

we dream to simulate real-life threatening situations (e.g. a physical attack, threats to relationships, threats to one's livelihood) to better predict and adapt to these events if/when they occur

• diurnal- active during daylight
• nocturnal- active at night

- mainly EEG

- supplemented by EOG (electroculography- measures eye movements) and EMG (electromyography- measures muscle tension)

medial prefrontal cortex and medial occipital cortex

- the ability to be aware that you're dreaming and in some cases the ability to even control the dream

- may have negative effects on dream quality

- increasing the likelihod of having a lucid dream: TES applied to the frontal and temporal lobes, some cognitive training techniques, administration of acetylcholine agonists

• increase in sleepiness
• falling asleep faster
• negative effects on mood
• worse attention and vigilance
• microsleeps
• increased efficiencyof sleep (higher proportion of slow-wave sleep)
• physiological effects: decreased body temperature, increased blood pressure, decrease in some immune functions, hormonal changes, metabolic changes, 

• adaptation theories
• recuperation theories

dreamlike experiences during wakefulness

- the inability to move as a person is falling asleep or waking up

- when entering REM sleep, the brainstem initates muscle atonia (reduced muscle tone to prevent us from acting out physically from dreams), but sometimes muscle atonia continues even after we wake up 

- caused by stress or exhaustion

- 90 minutes long

- 4-5 times a night

- stage 1 => 2 => 3 => 2 => 1

- as the night progresses, more time is spent in stage 1 and  less and less time is spent in stages 2 and 3

- involves REMs (rapid eye movements), cerebral activity in many brain structures increased to waking levels (O2 consumption, blood flow, neural firing), general increase in the variability of autonomic NS activity (blood pressure, pulse, respiration), occasional muscle twitches, some degree of penile/clitoral erection, emotion-charged

- the 1st REM is the shortest and the last REM is the longest

- a brief arousal occasionally occurs immediately after a REM period- the sleeper may shift their posture at this time

- memory strengthening theories

- the default theory of REM sleep- it’s difficult to continuously stay in NREM sleep, so the brain switches between 2 states: wakefulness if there are any immediate bodily needs that need to be taken care of (hunger, thirst) or REM if there are no needs to be taken care of

occurs during slow-wave sleep (never during REM sleeps beacuse of the complete realxation of muscles)

can occur during any stage