How Do Brain Waves Accelerate During Sleep?

iam really curious as far as brain wave states while sleeping. You know, you show some scans and the different brain wave statesthat one enters as they go deeper into stages of sleep. And thn someone, i'm somewhat familiar with brain wave states, and i was fascinated to see that gamma waves appear during rm sleep. Why do waves accelerate so fast when going from going from delta to gamma? So i think this is quite interesting because it allows us to go from biology to psychology. But if we look into the first half of the night, it's dominated by the slow wave sleep that you'e just mentioned.