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.