Why do we have dreams?
And where do dreams come from?
One of the most widely-accepted scientific theories about dreams
is J. Allen Hobson’s Activation-Synthesis Hypothesis . Hobson, a Harvard
neuroscientist, believes that dreams start out as random electrical sparks
during REM in the brainstem. He says that the electrical activity causes
weird, disconnected images and sensations in our minds. The cortex
("higher" area of the brain which handles complex thought) then tries to
make sense of the jumbled input, resulting in a dream.
Many other scientists agree with Hobson, believing that random
activation of the brain is responsible for creating dreams. Our brains may
need to stay somewhat active during the night, so the theory goes, so
that we are alert enough to wake up if there is danger. (During REM
sleep, our brainwaves do speed up and look more like our waking
brainwaves.) Or the random stimulation may simply be "exercising" the
neural pathways to keep the connections strong. Dreams may just be an
"accident" or a "by-product" of this exercise process.
Other scientists argue that REM sleep and/or dreaming may be
essential for learning and memory. They believe that we may actually be
building new physical or chemical connections within the brain as we
dream in REM sleep. Harvard’s Robert Stickgold and Trent University’s
Carlisle Smith are two of the researchers investigating this idea. Our
dreams may be an odd way of "eavesdropping" on the work that the brain
is doing as it processes new information and consolidates it in memory,
connecting it to older, previously stored information.
Crick & Mitchison’s Unlearning Theory says exactly the opposite,
that dreams don’t help us remember; they help us forget trivial and
useless information. This unlearning supposedly clears out mental space,
allowing us to re-use neural pathways to store new memories.
Still other scientists (such as Rosalind Cartwright) suggest that
dreams aren’t intellectual at all; rather, they are triggered by our
emotional reactions, and that they may be necessary for us to regulate
our mood. Researchers such as Milton Kramer and Ernest Hartmann
believe that dreams result from unresolved emotional issues that surface
during sleep.