A new theory suggests that dreams are a warm-up for the day ahead
Dreams are so rich and have such an authentic feeling that scientists have long assumed they must have a crucial psychological purpose. To Freud, dreaming provided a playground for the unconscious mind; to Jung, it was a stage where the psyche’s archetypes acted out primal themes. Newer theories hold that dreams help the brain to consolidate emotional memories or to work though current problems, like divorce and work frustrations. Yet what if the primary purpose of dreaming isn’t psychological at all?

In a paper published last month in the journal Nature Reviews Neuroscience, Dr J Allan Hobson, a psychiatrist and longtime sleep researcher at Harvard, argues that the main function of rapid-eye-movement sleep, or REM, when most dreaming occurs, is physiological. The brain is warming its circuits, anticipating the sights and sounds and emotions of waking.
“It helps explain a lot of things, like why people forget so many dreams,” Dr Hobson said in an interview. “It’s like jogging; the body doesn’t remember every step, but it knows it has exercised. It has been tuned up. It’s the same idea here: dreams are tuning the mind for conscious awareness.”

Drawing on work of his own and others, Dr Hobson argues that dreaming is a parallel state of consciousness that is continually running but normally suppressed during waking. The idea is a prominent example of how neuroscience is altering assumptions about everyday (or every-night) brain functions.
“Most people who have studied dreams start out with some predetermined psychological ideas and try to make dreaming fit those,” said Dr Mark Mahowald, a neurologist who is director of the sleep disorders program at Hennepin County Medical Center, in Minneapolis. “What I like about this new paper is that he doesn’t make any assumptions about what dreaming is doing.”

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