On asking about dreams with sleep medicine expert Michelle Drerup, PsyD, she said:
The majority of our dreams happen during REM (rapid eye movement) sleep, which we cycle through throughout the night. Our brainwaves are almost as active during REM cycles as they are when we are awake, according to sleep studies.
Experts believe that the brainstem is responsible for REM sleep and the forebrain is responsible for dreams. Why?
Patients who have had their brainstems injured dream but do not enter REM sleep. Patients who have had their forebrains injured go into REM sleep but do not dream.
Other things that happen during REM sleep include:
- You lose muscle tone so that you don’t hurt yourself by acting out your dreams. (REM sleep behaviour disorder lacks this protection.)
- Because you can’t regulate your body temperature by sweating or shivering, your body temperature drifts toward the room temperature.
- If you have sleep apnea, your breathing and heart rate become irregular during REM sleep, making it more noticeable.
- When you’re exposed to brighter light, your pupil constricts, possibly to protect your eyes.