Dreams & Memory
Interesting theory/finding on a practical purpose for dreams:
In the past, people often had one explanation for sleep and another for dreams. That now seems wrong. One of the chief functions of sleep seems to be achieved during dreaming: the consolidation of memory. Sleep certainly improves memory performance of several different kinds: emotional, spatial, procedural and verbal.
But the new thinking is that, during sleep, the brain reprocesses or transforms fragile new memories into more permanent forms, sets them in mental context and extracts their meaning. And dreaming is a symptom that this is going on.
According to this theory, dreaming is a symptom of such memory processing. Contrary to popular belief, dreaming occurs throughout sleep, not just in rapid-eye-movement sleep. But the dreams reported by people woken from non-REM sleep tend to be literal and straightforward recitations of recent experiences stored in the hippocampus. The later dreams of REM sleep incorporate more distant memories, becoming more fantastic and more emotional as the new memories get mixed with old ones in the cortex.
When we replay a recent experience in a dream, we enhance our memory.