Sleep and Dreams Flashcards
the role of the brain in sleep?
- scn triggers the release of melatonin when it receives info that suggests its getting dark
- scn also controls our circadian rhythm on a 24 hour cycle, even if there are no zeitgebers or when travelling across time zones.
- adenosine builds up in our neutrons as a natural by-product of the brain’s daily activities, leading us to feel tired later on in the day.
- if scn confused about what time it is due to zeitgebers, melatonin may be released at wrong time, or not at all.
- adolescents have a natural delayed sleep phase (sleep and wake later) - blue light from their devices suppresses release of melatonin.
circadian rhythms?
- body clock, sleep/wake cycle
- scn controls circadian rhythm
- scn controls the release of melatonin, scn sends signals to the pineal gland which then releases the melatonin. the release doesn’t make people feel instantly tired, is usually released early evening.
REM sleep?
- rapid eye movement
- where dreams most likely occur
- muscles are paralysed, cannot act out our dreams, even though brain is very active
- brain waves similar to when awake, a.k.a paradoxical sleep.
- important in creation of long term memories and pyschological functions.
NREM sleep?
- unlike REM, sleeper not fully paralysed
- continuous low-level muscle movements in the neck and jaw muscles
- ‘slow wave sleep’ brain waves = larger and slower
- important for physiological repair e.g., growth hormones released.
Explain Oswald’s Restoration theory
- main function of sleep is to allow repair and maintenance of the body and mind.
- repairing minor injuries, such as skin or muscles.
- removal of waste chemicals in the muscles
- repenting neurotransmitters and/or energy in the brain
- period of physical inactivity might be essential to allow restoration to happen
- sleep causes the body to be relatively active - repair functions may be more successful during inactivity as no further damage to body tissues, or no fewer toxins/waste products are being produced.
EVIDENCE, PETER TRIPP AND RANDY GARDNER.
Oswald’s Restoration Theory Strengths
- sleep helps us recover from physical exertion. research shows that longer sleep (esp. stage 3) occurs after large amounts of exercise.
- Shapiro (1958) very long distance runners running a double marathon slept for longer, suggesting sleep aids restoration. their sleep lasts an average 90 minutes longer than usual over next 3 weeks, NREM lengthened, rising from 25% to 45% of total sleep.
- amount of REM sleep varies according to needs of life stage, growing children need more (REM =’ 50% babies sleep and 20% adults)
- negative effect of sleep deprivation, affects the immune system.
- Zager et al (2007) - rats sleep deprived for 24 hours, compared with control group, sleep deprived rats blood indicated a 20% decrease in white blood cell count.
Oswald’s Restoration Theory Weaknesses
- Lavie et all (1984), 20 year old suffered shrapnel brain injury, experienced no REM sleep and completed his education, became a lawyer.
- Horne (1978) 50 studies of sleep deprived humans, found very few reported deprivation interfered with ability to physical exercise.
- no evidence of physiological stress response to sleep deprivation.
Dement and Kleitman’s study
A: find out if relationship between REM sleep and dreaming.
M: laboratory experiment, 9 adult participants, asked to avoid caffeine and alcohol on day of study.
P: observed sleeping over numerous nights, repeated wakenings. EEG measurements recorded brain and eye activity. Participants asked to report dreaming and what about.
R: Rem sleep linked to dreaming in most causes, patterns of eye movement showed a link with the type of dream the participant recalled. duration of rem also showed a relationships with the reported duration of the dreams.
C: An objective measurement of dreaming accomplished by recording REM during sleep. Became possible to study effect of dreaming on environmental changes, psychological states, drug administration, and a variety of other factors and influences.
Dement and Kleitman’s study strengths
- other recent research appear to confirm findings that dreaming is linked to REM sleep
- research such as D&K allowed other psychologists to study the link between sleep and dreams and the purpose of them may be
- controlled environment
Dement and Kleitman’s study weaknesses
- ecological validity, conducted in artificial setting (laboratory)
- very different environment from normal routine - results not applicable to real life situations
- not all dreams happen during REM sleep, hypnogogic dreams occur during NREM, shortly after falling asleep, experiencing the sensation of falling/ being out of control. often wake up with a jolt (hyping twitch)
- individual differences, differences in sleep patterns are usually non-biologically factors e.g., room temperature and sleep hygiene.
- Tucker et al (2007) suggests differences are bio determined, not genetic. ppl studied over 11 days/nights in controlled lab, assessed sleep duration, time to fall asleep and amount of sleep in each stage, LARGE INDIVIDUAL DIFFERENCES, esp. deep sleep (3 and 4).
Cognitive processes
- problem solving and consolidating memories
- brain reorganises memories during sleep and that dreams occur as a by-product of this process, as various memories are strengthened or changed
- similar to activation-synthesis theory, both seem dream content as no deep meaning
- WAGNER 2004 - gained better insight after sleeping
- GAIS ET AL 2006 - English and German words remembered better after sleep straight after learning
- CARTWRIGHT 1984 - dreams are for problem solving, mind finds symbols to reflect emotional concerns and issues.
Crick and Mitchinson’s 1986 Reorganisational Theory
- main function of dreams is to make the most of our ability to store memories
- brain’s storage capacity is limited, some memories deleted overnight in order to create space
- reverse learning, learning can be undone during REM sleep
- ‘we dream in order to forget’
- brain = overloaded, cannot function quickly and efficiently as usual
- when asleep, brain can streamline unneeded info
- compared to computer, cleaning hard drive
- negative consequences = can lead to obsessive thoughts if not carried out
- adaptive dreams = useful
- parasitic = useful/harmful
Reorganisational Theory - Strengths
- helps explain bizarre imagery and thoughts that occur after periods of sleep deprivation. the brain has not had chance get rid of parasitic memories
- helps explain why we forget 95% of our dreams, they are discarded because they only clog up and prevent access to important info we need
- has some face validity
Reorganisational Theory - Weaknesses
- if memory elimination is primary function of REM sleep, unclear why babies prior to birth spend 50-80% of their sleep in REM, given that they have a minimal requirement for reverse learning.
Czeisler et al’s (1990) study
A: find out if exposure to bright light at night and darkness during the day could prevent disturbances in the sleep wake cycle caused by working night shift.
M: 8 men took part in a 2 week lab experiment. attended the lab for 6 days of shifts - stayed awake, undertook cognitive tests and reported on their alertness and mood.
P: men in experimental group exposed to very bright light during their night shift
R: experimental group reported better alertness and mood, adjusted their circadian rhythm whereas control group stayed the same.
C: adapting to night shift work can be successful with properly timed exposure to bright light during nightshift and darkness during daytime sleep
