Answer:
It was the electroencephalograph (EEG) development that enabled researchers to study rest in manners that were not already conceivable.
Step-by-step explanation:
You've most likely heard that you progress through a progression of stages as you rest, however what precisely does that mean? Rest is rest, isn't that so?
As a general rule, there is still a great deal going on inside your head while you're in sleep, and it is the action in your cerebrum that denotes these diverse rest stages.