Activation Synthesis Theory of Dreaming

This was proposed in 1977 by Robert McCarley and J. Allan Hobson of Harvard Medical School. The hypothesis he proposed was that dreams had no meaning, and his ideas were based on purely physical grounds.

He saw that during rapid-eye-movement sleep the brain produces electrical signals that stimulate several areas of the brain including those connected with movement, the senses and speech. The thought was that these were all random, but the themes come from the higher mental centres imposing order to make sense of what was seen as without meaning.