What Causes The Child To Scream Unknowingly While Sleeping?

Okay. I m adopted, so I don t know a whole lot about my family history. But before I was adopted I was in foster homes and one took me to the doctor when I was only an infant about screaming in my sleep. Turns out, every since I was a tiny little thing I would scream so horridly that it d wake up everyone in the house. I, myself, however didn t know I was screaming. The only thing that would wake me up would be if someone shook me awake. I didn t know why they woke me up. I never remembered even screaming. I was not even dreaming or having a nightmare. Everything was just black. My currently adoptive parents told me this when I was old enough to understand, but they said that my doctor said it was no sleep or night terrror. They don t remember what she said. I think she possibly didn t even know what it was.