Crick and Mitchinson's Cleanup
          Crick and Mitchinson base their theory on the fact that the cortex, unlike other parts of the brain, is made up of richly interconnected neuronal networks in which each cell has the capacity to excite it's neighbors.  It is believed that memories are encoded in these networks and when one point of the web is excited a pulse travels through the network prompting recall.  The problem with such network systems is that they malfunction when there is an over load of incoming information.  Too many memories in one network may produce either bizarre associations to a stimulus, which creates our fantasies, the same response whatever the stimulus, creating obsessions, or associations triggered without any stimulus, which creates hallucinations.
          To deal with information overload, the brain needs a mechanism to debug and tune the network.  This debugging mechanism would work best when the system was isolated from extermnal inputs and it would have to have a way of randomly activating the network in order to eliminate spurious connections.  This method, they say, is REM sleep and that the halluinatory quality of dreams is nothing more than the random neural firing needed for the daily cleanup of the network.
          According to this theory, these signals somehow erase the spurious memory associations formed during the previous day and we wake up with the network cleaned up.  They believe that people remembering their dreams could help retain patterns of thought which are better forgotten, the same patterns that your system has attempted to clean out.  This is why, they say, if you don't write down your dreams they will be forgotten because your brain is still working to clear these memories out.
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