Yeah. Have you ever memories that pop up only when you're drunk?
It's the same idea. When you're at a certain state: body
temperature, certain state of sleepiness... every dream you ever
had when your body was in that state previously, whether you
were 6 yrs old, ,9 yrs old, 20 yrs old, whatever, will be a
"match" for your body/mind state and will start flooding in. I
enjoy the flood. It's fun watching them whizz by.