Outline and evaluate one neurobiological theory of dreaming and one psychological theory of dreaming

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a) Outline and evaluate one neurobiological theory of dreaming

One neurobiological theory of dreaming is the activation-synthesis hypothesis, which suggests that the brain stem generates random signals as it does when you’re awake due to internal and external stimuli (Hobson and McCarley, 1977). However, unlike when you’re awake, during sleep there is a sensory and motor blockade i.e. no input from senses and no control of muscles due to paralysis so there is a lack of internal and external stimuli but EEG recordings show that the cortex is still active in REM sleep. The only muscles that are allowed to move are those controlling the eyes, hence REM sleep is called rapid eye movement sleep. Dreams are supposedly created during the synthesis part of this process. When the activation (the random signals) reaches the frontal cortex, it essentially does the same job as when we are awake. It tries to make sense of the stimuli being received. Dreams are often of a strange nature because of the combination of the electrical signals from the brainstem and stored images in memory and because the brain attempts to invest the dream with meaning. Hobson (1988) believed that dreams are no more than reactions to random nervous system stimuli, which the brain “interprets” as peculiar images and other sensory illusions.

Research to support this theory comes from recent developments in brain scanning techniques. PET scans show the brainstem is active during REM sleep (Braun et al., 1997). PET scans have also shown that other areas of the brain are active during REM sleep such as those responsible for more complex mental processes such as emotion, memory reinforcement, hearing and vision. At the same time, areas in the prefrontal cortex associated with things such as rational thought and other more sophisticated mental processes appear to be shut down. This supports the activation-synthesis hypothesis because it shows that parts of the brain are still active whilst other parts are inactive.

However, evidence from studies of patients with brain damage indicates that REM is linked to the brainstem but not dreaming. This is not predicted by the activation-synthesis hypothesis.

Solms (2000) found that with injuries only to the brainstem, REM activity almost invariably ceased but dreaming continued. In other patients, damage to areas of the forebrain had no effect on REM sleep but dreaming ceased. The activation-synthesis hypothesis suggests that REM sleep and dreaming are linked and that dreaming cannot occur without REM. This evidence causes us to question the validity of the activation-synthesis hypothesis.

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Further evidence to question the hypothesis comes from research by Rittenhouse et al. (1994) who found that, most of the time, dreams were meaningful and coherent. He studied over 200 dreams and found that only 34% had discontinuities i.e. things that didn’t make sense. This means that the majority of dreams were not random or meaningless. This contradicts the view of the activation-synthesis hypothesis, which suggests that dreams are just the result of random signals being sent from the brainstem. If this were the case, then surely we would never have the same dream twice or be able to understand ...

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