[Added November 1997]
According to recent studies,dreams may reflect a fundamental aspect of mammalian
memory processing(only mammals dream).
The long term memory of crucial information acquired during the waking
state seems to require the reprocessing of this information during the
REM phase of sleep when we dream.
To avoid interference with sleep of the re-enacted experience the motory
neurons that command our muscles are inhibited, except for those that
command our eye movement.
Everything seems to start with activation
of hippocampus a part of the brain involved with memory processing.
The kind of memory which is more influenced by sleep and dreams is
the implicit procedural memory. This should be “obvious” from the fact
that also animals dream and animals have only this kind of memory.