W8 - sleep ✅ Flashcards
Introduction and stages • Neural control of sleep (Physiological mechanisms of sleep and waking) • Why do we sleep Disorders of sleep
What are the features of stage 1 of sleep?
- Theta activity 3.5 – 7.5Hz
- Firing of neurons in the neocortex becoming more synchronised
- sleep - wakefulness transition
- Last ~10 mins
What are the features of stage 2?
- Irregular EEG during this stage
- Theta activity like in Stage 1
- Sleep Spindles – short bursts of waves of 12-14Hz that occur between 2-5 times/min -> more number of sleep spindles is associated with higher IQ
- K Complexes - consolidation of memory
What are the features of stage 3 & 4? How to distinguish them?
- High amplitude delta activity – Slower than 3.5 Hz
- Slow wave oscillations <1Hz
- Down state and up state
- Stage 3: 30-50% delta activity
- Stage 4: >50% delta activity
What are the features of REM sleep?
- Rapid eye movements
- EEG De-synchrony – rapid, irregular waves
- Dreaming
- Loss of muscle tone – paralysis
- Cerebral blood flow and oxygen consumption are accelerated
- Mechanisms that regulate body temperature stop working
- If woken the person will usually appear attentive and alert
What are 5 neurotransmitters that play a role in arousal?
- Acetylcholine:
- High in Neocortex and hippocampus
- High amount = wakefulness - Norepinephrine
- High in locus coerulus
- Involved in wakefulness & hypervigilance - Serotonin
- High in raphe nuclei
- Regulating bodily function, locomotion and cortical arousal
- Declining as sleep progress, close to zero in REM
- Fast increase after REM sleep ends - Histamine
- High in hypothalamus
- High activity = wakefulness, slow = sleep - Orexin
- High in hypothalamus (secreted in hypocretin)
- Excitatory effects in cerebral cortex + regions involved in sleep/wakefulness
- In mice, highest orexin activity during exploration & active waking, lowest in sleep (esp. REM)
What are the 3 factors that control sleep?
3 factors: homeostatic, allostatic, and circadian
- Homeostatic: presence/absence of adenosine
- Allostatic: hormonal & neural responses to stressful situations
What are the features of dreams, nightmares and lucid dreaming?
DREAMS:
- Occur every night
- Little evidence of adaptive function
- May represent threat-stimulation
- Parts of brain active in a dream would also be active if the events were occurring irl
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NIGHTMARES: - Defined as a vivid and frightening dream that awakens the dreamer
- Idiopathic (just general scary imagery, non-traumatic) and post-traumatic nightmares
- 2-5% population experience frequent nightmares
- Causes unclear but greater experience associated with:
1. PTSD
2. depression
3. insomnia
4. being female
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LUCID DREAMING: - Awareness that you are dreaming while the dream continues
- Can be trained and be induced -> applying tACS to brain
- Lucid dreaming induced at two frequencies: 25 and 40Hz -> associated with lower gamma frequency in the fronto-temporal brain area
Functions of Slow-wave sleep?
- Let the brain rest
- Slow-wave sleep deprivation affects cognitive abilities, especially sustained attention, but not physical abilities
- Slow down cerebral metabolic rate and blood flow (falls by ~75%)
- Facilitate consolidation of explicit (declarative) memory
Functions of REM sleep?
- Rebound of REM sleep (not enough REM sleep in 1 cycle -> more in next cycle)
- Consolidation of implicit memory
- Highest proportion occurs during brain development
- Possible to function normally without REM sleep with no obvious side effects -> shown by ppl on antidepressants or with brain damages
What are some sleep disorders?
- Insomnia
- Sleep Apnea
- Narcolepsy
- REM sleep behaviour disorder
- Slow-wave sleep problems
- Fatal familial insomnia
Insomnia
Symptoms:
- difficulty getting to sleep, staying asleep, or having non-restorative sleep
- plus impairment of daytime functioning
How common: ~9% population while up to 1/3 has >1 nocturnal symptoms
Effects: chronic sleep deprivation can lead to serious health problems
Causes of insomnia:
1. Age: older people
2. Environmental factors
3. Physiology: Heightened activity in the reticular activating system
4. Changes in circadian rhythms (e.g. time zone, work pattern)
5. Medical conditions and medications
Treatment for Insomnia: Drugs (block neurotransmitters involved in arousal, CBT)
Sleep Apnea
A form of insomnia - stop breathing when sleep
Cause: build-up of CO2 -> stimulates chemoreceptors to prevent sleep
Effect: affect daytime functioning
Treatment: if caused by obstruction -> corrected surgically OR pressurised air (keep airway opens)
Narcolepsy
The brain is unable to regulate sleeping and waking patterns normally.
Symptoms:
- Sleep attack – overwhelming urge to sleep
- Cataplexy – temporary loss of muscle control resulting in weakness and possible collapse, often in response to emotions such as laughter and anger (REM sleep mechanism)
- Sleep paralysis: just before waking or falling asleep
- Hypnogogic hallucinations: dreaming while awake, just before sleeping AND paralysed
Causes:
- Hereditary element
- Environmental factors
- Orexinergic neurons being attacked by the immune system
Treatments:
- Ritalin -> counter sleep attacks
- Antidepressant drugs -> counter REM sleep phenomenon
- Modafanil and/or sodium oxybate (GHB) -> stimulant drugs
REM Sleep Behaviour Disorder
- Acting out dreams -> failure to exhibit paralysis during REM sleep
- Neurodegenerative disorder with a genetic component
- Associated with other neurodegenerative conditions such as Parkinson’s disease
- Usually treated with clonazepam -> reduce symptoms - commonly used to treat anxiety
Slow-Wave Sleep Problems
- Sleepwalking (somnambulism)
- Person can engage in complex behaviour
- More common in children
- Genetic component
- Disorder of arousal - Night terrors (pavor nocturnus)
- Anguished screams, trembling, rapid pulse, and no memory of what caused the terror
- Hereditary elements - Bedwetting (nocturnal enuresis)
- About 10% of 7 year olds
-Hereditary elements
Fatal Familial Insomnia
Neurodegenerative condition
- Prion disease
- Damage to the thalamus
Progress:
- Initially presents with insomnia and very vivid dreams.
- Psychiatric complications – panic attacks, cognitive deficits, paranoia and phobias.
- Affects the autonomic nervous NS and coordination (ataxia)
- EEG shows disturbances and reductions in sleep spindles and K complexes -> lost of slow-wave sleep and only brief periods of REM sleep
- Ultimately inability to voluntarily move or speak (akinetic mutism), coma, and death.
