Sleep and Dreams Flashcards
Biological Approach - The role of the brain in sleep
The SCN is a small part of the hypothalamus in the brain which controls the circadian rhythm. Detects light from the optic nerve and sends a signal to the pineal gland when sunlight decreases.
The pineal gland produces melatonin which is a hormone that makes us feel sleepy.
Adenosine - a chemical that builds up during our waking hours which increases the pressure to sleep.
Biological Approach - Circadian Rhythms
Circadian rhythm - A biological clock that controls periods of activity and inactivity which fluctuates on a roughly 24 hour timetable.
For example, some people feel more energetic/alert at certain points during the day and run-down at others.
Biological Approach - Circadian rhythms (evidence)
Michael Siffre lived in a pitch black cave for 63 days and found his circadian rhythms changed to more of a 25 hour cycle - but he still had an internal clock. Shows we have inbuilt circadian rhythms but our brain has the role of adjusting this rhythm.
Biological Approach - Non-REM and REM sleep and dreaming
N-REM:
Stage 1- Relaxed wakefulness, drifting off, easy to awaken, muscle jerking can occur.
Stage 2- Heart rate slows and body temperature decreases. Block out external stimuli and possible memory consolidation, harder to wake up.
Stage 3/4- Deep sleep, people hard to wake up, parasomnias occur.
REM- Eyes move under eyelids, irregular breathing and higher blood pressure, temporary sleep paralysis, dreams.
Evidence- Dement and Kleitman
Biological Approach - Oswald’s Restoration Theory
The theory suggest that the main purpose of sleep is the restoration of the body.
The theory suggests that the nREM sleep does this by repairing cells during sleep, replenishing sources of energy and aiding in the removal of waste chemicals built up during the day.
REM sleep restores the brain by aiding psychological recovery, replenishing supplies of neurotransmitters and restoring supplies of brain proteins.
The reason why these restorations occur during sleep is because it is inactive so no new resources are being used.
Biological Approach - Evaluation of Oswald’s Restoration Theory (Strengths)
Strength - Restoration is a key explanation of why all mammals sleep and is better able to explain the loss of consciousness compared to alternative ideas.
Strength - Supported by lots of evidence, including Rechtschaffen rat study; Savard’s insomnia and immune cell study and Shapiro’s ultramarathon runner study.
Strength - Further findings support this idea as they have found that many major restorative functions occur mostly or only during sleep.
Biological Approach - Evaluation of Oswald’s Restoration Theory (Weakness)
Weakness - Most of the evidence for this theory is from correlation studies and do not show cause and effect.
It is over simplistic to say the only purpose of sleep is restoration as sleep most likely has multiple functions.
Biological Approach - the aims, methods, results, and conclusions of Dement and Kleitman.
Aim - Investigate the relationships between sleep stages and dreaming. To investigate the relationship between eye movements and dream content. To investigate the function of REM sleep.
Method - Took place in a sleep lab, 9 participants (7 males, 2 females). They were asked to avoid alcohol and caffeine the day of the study. they did a PSG to monitor their brain activity and eye movement. Participants were woken up several times at night by researchers and were asked if they had been dreaming, what they had been dreaming about and for how long they had been dreaming for.
Results - 80% of the time when participants were woken up during REM sleep they said they were dreaming while only 9% of participants said they had been dreaming during nREM sleep.
Results - The study found that eye movements were related to dream content, for example someone having left to right eye movement dreamt of people throwing tomatoes at each other.
Biological Approach - Evaluation of Dement and Kleitman (strength)
Took place in a sleep lab so ev’s could be controlled to ensure participants weren’t woken up unless it was on purpose.
Eliminated demand characteristics using single blind study so participants didn’t know what stage they were woken up during so they couldn’t fake the results.
Biological Approach - Evaluation of Dement and Kleitman (weakness)
The small sample size so the results can’t be generalised.
The sample included all adults - no children so we don’t know if they follow the same pattern when it comes to dreaming.
There was a gender imbalance in the sample which makes the results harder to generalise.
Artificial setting of the lab and being frequently disturbed during sleep reduces the ecological validity of the results.
Unethical as the sleep of participants was disturbed
Cognitive Approach - How sleep facilitates information processing
This approach compares the mind to a computer with the way it processes information as it says that during sleep the mind can “clear up files” which strengths the links between memories. In this analogy sleep is helping the storage part of the brain by pruning out unnecessary items and strengthening links between memories.
Another reason for the computer analogy is that mental processes follow a clear sequence which is:
Encoding of sensory information –> Information manipulation (mental processes) –> Output (e.g. behaviour, emotion).
Cognitive Approach - Crick and Mitchison’s Reorganisational Theory
This theory suggests that the main purpose of dreams is reorganisation in order to improve memory storage.
Dreams are a side effect of the decluttering process.
Suggests there are two types of memories; adaptive (things that will be useful for us to retain) and parasitic (useless or harmful memories that are wasting resources).
Crick and Mitchison wrote “We dream in order to forget”.
Reverse learning is a process that happens during REM sleep that removes these parasitic memories from our memory.
The cortex of the brain is overloaded during the day, and during REM unwanted memories are deleted to make space for new memories.
For example you might not remember what you had for dinner last week because it was deemed a parasitic memory.
Cognitive Approach - Evaluation of Reorganisational Theory (Strength)
Huber et al found that nREM sleep can increase some forms of learning which supports Crick and Mitchison’s prediction that the function of sleep is cognitive restoration.
Larger brains exist in animals that don’t have REM sleep which supports the theory as it suggests that these animals need more room for parasitic memories.
It gives a clear theory about why REM sleep specifically could be important. By making memory more efficient, Crick and Mitchison argue that better use is made of the available space in the brain.
Cognitive Approach - Evaluation of Reorganisational Theory (Weakness)
It lacks support on human participants as the only evidence Crick and Mitchison have is based on dolphins and enichdas which cannot be applied to humans.
Doesn’t explain why our dreams have a story and make sense majority of the time. Doesn’t fit well with the idea of dreams being a result of a random decluttering process.
If harmful memories are deleted during sleep, then those suffering from PTSD wouldn’t experience nightmares where they relive their trauma.
We now know that humans an unlimited long term memory capacity, so the need to delete memories would be pointless.
Multiple studies have found that sleep is beneficial to memory, rather than destroying memories. There is no evidence that memories are deleted during sleep.
Cognitive Approach - Czeisler’s study into night shift workers
Aim - To find out whether disturbances in the sleep-wake cycle created by working at night could be prevented through being exposed to bright light at night and darkness during the day.
Method - Sample of 8 healthy men from ages 22-29 took part in a lab experiment. They had no medical, mental health or sleep disorders. They also were not taking any medications and did not have any alcohol or caffeine and were urine checked. The men came to the lab at night to do “shifts” of cognitive tasks and reported their mood and alertness. There were two groups; a control which was exposed to normal light and slept in normal conditions and an experimental group who were exposed to very bright light and slept in blacked out conditions.
Results - On average the experimental group slept 7.7 hours a night while the control only slept 5.7 hours a night. Biological measures showed that the experimental group’s circadian rhythms moved forward by 9 hour
