Biological Rhythms and Sleep Flashcards
What are the three biological causes of narcolepsy?
Abnormal REM sleep, a mutation of the immune system and low levels of hypocretin.
Why is REM sleep abnormal in narcoleptics? (Vogel)
How does this explain the disorder?
It occurs at the onset of sleep and is abnormal at night.
Some of the symptoms of narcolepsy, such as loss of muscle tone and hallucinations are found in REM sleep.
What did Honda et al find which suggests that narcolepsy is caused by the immune system?
90% of narcoleptics have and increased frequency of HLA, which coordinates the immune response.
What is the role of hypocretin?
How does it cause narcolepsy?
Hypocretin regulates the sleep-wake cycle with the hypothalamus.
There is a link between low levels of hypocretin and the disorder.
What did Lin et al find to support the role of hypocretin in narcolepsy?
Narcoleptic dogs had a mutation in a gene on chromosome 12 which disrupted the way that hypocretin was processed.
AO2 - What evidence make hypocretin the most likely explanation of narcolepsy? (2 things)
Findings in dogs have been replicated.
Nishino et al- humans had low levels of hypocretin in their CSF.
AO2- What did Mignot find which makes it difficult to explain the low levels of hypocretin?
There is no significant risk of both twins developing narcolepsy; the disorder is not genetic.
AO2- What might cause the hypocretin abnormalities?
Brain injury, infection, diet, stress or an auto-immune attack (this would link to HLA abnormalities by Honda et al).
AO2- Explain how the psychoanalytic approach would explain narcolepsy. (Lerham and Weiss)
Sudden onsets of sleep are a way of disguising sexual fantasies and arousal, or of coping with them and reducing anxiety and distress.
AO2- Why is the psychoanalytic view a minority view?
Narcolepsy has clear physiological element meaning that biological factors are more likely to cause it.
AO2- What is wrong with the explanations of narcolepsy ? (2 things)
They are reductionist - they reduce the disorder to a malfunction in a specific biological system = oversimplified in and artificial way.
They are deterministic - the individual cannot bring the disorder under their control.
AO2- What is the problem with the use of animals in narcolepsy studies? Why?
The findings can’t be generalised to humans as humans and animals have a different anatomy and physiology and different sleep patterns. Plus, humans have the ability to think about their experience while animals cannot, which may affect the way they sleep.
AO2- What is positive of using animals to study narcolepsy?
The findings have been replicated in humans.
What are the symptoms of narcolepsy?
Sudden and uncontrollable attacks of sleep that last 10-20 minutes. Sufferers often have cataplexy too, where they have a loss of muscle control leaving them mentally awake but physically paralysed (like REM)
How does ‘incomplete arousal’ explain sleep walking?
The sleep walker is in a deep sleep but is partly awake as the carry out activities associated with being awake. (Their brain has a mixture of Delta Waves, typical of SWS, and Beta waves, typical of waking brain)
What are the risk factors for sleep walking? (6)
Sleep deprivation, alcohol, fever, stress, psychiatric conditions and hormonal changes
What percentage of children sleep walk?
Why are children more likely to sleepwalk than adults?
20%
They have more SWS than adults.
What does Olivero suggest is the reason that children sleepwalk?
The system that inhibits motor activity during SWS is not sufficiently developed in some children and adults.
What did Olivero examine?
What did he find?
The motor excitability of adult sleep walker during wakefulness.
Sleepwalkers had signs of immaturity in the relative neural circuits.
AO2- What did Broughton find to show a genetic basis for sleep walking?
The prevalence of sleep walking in 1st degree relatives of an affected subject is 10 times greater than in the general population.
AO2- What did Lecendreux et al find to show a genetic basis for sleep walking?
A 50% concordance rate in MZ twins compared to a 10-15% concordance rate in DZ twins. They also identified a gene that may be critical in sleep walking (DQB1*05)
What is the diathesis-stress model?
An individual will have a vulnerability to a disorder due to their genes but it will only appear if triggered by a stressor.
AO2- What did Zedra et al do to find out if the diathesis-stress model can be applied to sleep walking?
What did they find?
What does this show?
They studied 40 patients in a sleep lab who were suspected of sleep walking. They prevented them from sleeping while there.
On the first night, 50% of patients showed sign of sleep walking. This rose to 90% of the second night.
> Sleep deprivation doesn’t cause sleep walking in normal individuals ; sleep deprivation = the stressor for vulnerable individuals.
AO2- How does the diathesis-stress model relate to children?
More likely to sleep walk as high levels of SWS are the diathesis.
AO2- What is the proposed psychological cause of sleep walking?
Why is this unlikely?
Acting out dreams representing repressed traumas and anxiety.
Sleep walking occurs during SWS when dreaming is not possible.
What waves are present during the 4 stages of NREM sleep?
Stage 1- Beta and alpha waves (fast and low altitude)
Stage 2- Theta waves & sleep spindles (phases of fast EEG activity that last 1 second and have K complexes)
Stage 3- Delta waves (slow and long altitude) start to appear and sleep spindles decrease
Stage 4 - Delta waves = deepest stage of NREM
What happens in REM sleep? (paradoxical sleep)
The brain and eyes are active but the body is paralysed
Beta waves are present (fast and desynchronised)
Why is the sleep cycle ultradian when the sleep-wake cycle is circadian? (sleep elevator)
There are 5 cycles of sleep each night which last about 90 minutes - this cycle occurs more than once every 24 hours.
SWS only occurs in the first two cycles. REM occurs in all and increases during the night
AO2 - What objective measures have been used to distinguish the stages and cycles of sleep?
Why are these more reliable than self-report?
EEGs -measure brain waves
EOGs -measure eye movement
EMGs - measure muscle movement
These are less subject to bias
AO2 -What are the problems with the sleep lab? (2)
It is an artificial setting - lacks ecological validity
It is reductionist - can’t reflect factors that affect sleep in real life
AO2- Are the findings universal?
Stages of sleep
Yes- stages 3 and 4 occur only in the first two cycles and and REM sleep always increases through the night.
This means that the finding have validity and are reliable
AO2- Why are there individual differences in the sleep wake cycle?
The study shows that 5 sleep cycles occur in around 8 hours but many people sleep more or less than this.
AO2- What is wrong with the self-report method? (2) (sleep-wake cycle)
It is vulnerable to bias and distortion due to researcher effects and participant reactivity. The data is also subjective and reliant on memory.