The identification of rapid eye movement (REM) sleep in the early 1950s gave researchers a reproducible physiological state in which vivid dream reports were especially common. It helped move dream research into the laboratory, but it did not establish that all dreaming occurs during REM.
REM sleep is characterised by distinctive eye movements, changes in brain activity and reduced skeletal-muscle tone. Researchers found that awakening people from REM frequently produced vivid dream reports. Later work showed that dreams and dream-like mentation can also occur during non-REM sleep.
REM therefore provided an important experimental window rather than a complete biological explanation of dreaming. The functions of REM sleep and dreaming remain active research questions, including possible relationships with learning, memory and emotion.
Claims that dreams “clear” memories, remove emotional charge or are required for a specific psychological function go beyond what the evidence can currently establish. The major historical advance was methodological: subjective dream reports could now be studied alongside measurable sleep physiology.
