(from the Harvard Neuro WordPress blog)
What are dreams, and why do we have them? People have probably been asking these questions since the dawn of reflective thought, but it wasn’t until the 1950s that scientists first identified neurophysiological correlates of dreaming. A classic paper by Aserinsky and Kleitman1 in 1953 marked the discovery of what we now refer to as Rapid Eye Movement (REM) sleep (Figure 1). Together with non-Rapid Eye Movement (NREM) sleep, REM sleep… (continued at link below).
Source: The neurobiology of dreaming