It’s been roughly 54 years since a young graduate student discovered and named REM sleep, which is commonly known as the “dream state.” While it is true that dreaming can occur in all of the sleep states (as cognition, mental imagery, and uncanny kinesthetics), it is REM that grants us the long dramatic dreamy narratives that we usually remember in the mornings.
REM stands for Rapid Eye Movement, and was named by young E. Aserinsky because, in this sleep state, every voluntary muscle in the body is in motor paralysis, except for the eyes. They roll back and forth wildly while the rest of the body remains frozen.
Every once in a while, we may have the experience of becoming aware during REM, and sensing the muscle paralysis. This effect can be terrifying or transcendental, depending chiefly on our previous experience with working with sleep paralysis, also known as night terrors.
The terror of sleep paralysis can feel like being held down, like a great weight on the chest, making breathing difficult. This is merely REM doing its thing, not anything to worry about. However, some studies have linked high rates of sleep paralysis to a dangerous condition known as sleep apnea. If you have trouble breathing when you sleep, and wake up often and sporadically, you may be suffering from sleep apnea.
Mostly though, we can be thankful for REM. It holds us down and keeps us safe while we live out our dream lives, swash-buckling around in our imaginations. Without this helpful mammalian adaption, we would constantly act out our dreams as we dreamed them. To put it mildly, those people in the deep past who did not have REM to keep them still while they dreamed are not our ancestors. Just like Spy.