Neurobiological explanations of Dreaming

AQA unit 4 - sleep and dreaming - neurobiological explanations of dreaming

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Neurobiological explanations of dreaming
1. Reverse Learning ­ Crick and Mitchison (1983)
Function of dreaming is to get rid of useless information ­ "parasitic information" ­ stored in the
brain as it used up valuable space in the cortex. It disrupts efficient organisation of memory
needed as our cortex contains many networks that are interconnected parasitic info means
unwanted connections are made. Dreaming allows us to read out and destroy the parasitic info,
so the dream is a byproduct of reverse learning.
Hobson (1994) Levels of serotonin and noradrenalin are lower in REM sleep than NREM, this
may explain why we forget dreams. Also, lower levels of them prevent us from paying attention,
so its easier for the brain to misinterpret signals as if they came from the outside world rather
than the brain = dreams.
Crick + Mitchison (1983) Cortex size. The only mammals not to have REM sleep are dolphins
and spiny anteaters and both species have really big cortex's.
theory doesn't explain all types of dreams
some dreams are meaningful
foetus' dream, or at least have REM sleep
Are our brains likely to run out of space?
Theory is not falsifiable ­ only looks at REM sleep
Positive points
We usually forget our dreams
Dreams are often about what we've experienced during the day
Dreams sometimes make sense
Very reductionist because it says dreaming is only about sifting out the rubbish we don't need
to remember because our brains are too small. We only use 16% of our brains it says there's
no meaning to dreams and not all dreams make logical sense.
2. Activationsynthesis theory ­ Hobson and McCarley (1977)
Activation: During dreaming there are highlevels of activation in parts of the brain ­ vision,
hearing, action and emotion. Little activation in areas related to smell or taste. Activation is
random and does not relate to external stimuli.
Synthesis: Humans search for meanings in things. We interpret the random activation as if it
were produced by external stimuli, so we experience dreams. This is why dreams often make
little sense ­ trying to synthesise random brain activation.
Hobson (1994) As before.
Hobson (1988) Research on cats indicated that there is an apparent random firing of brain cells
during REM sleep the areas that are activated do link to visual perception and the control of
many dream are coherent
Some dreams are meaningful ­ this theory suggests none are.
It cannot explain dreams that make sense and seem logical.
Not all dreams occur in REM sleep
Positive points
Animals have REM
We do not dream about smell and taste
Less reductionist than other theories as explanation is complex, but only takes into account
biological factors.


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