In which stage (s) of non-rem sleep do brain waves become larger and punctuated with occasional sudden bursts of electrical activity? ?

The second stage is where the brain waves become larger and punctuated with occasional sudden bursts of electrical activity. In this stage the eyes are not able to respond to light. Non-rem sleep has 3 stages. The first stage is the twilight zone which is between full wakefulness and sleep and the third stage constitutes the most profound state of unconsciousness.