THAT is interesting, and something I haven't really thought about in relation to hearing these voices and visions and such. I have a very good friend, from childhood, who was diagnosed with dissociative disorder. She started (started?---maybe finally admitted) hearing voices. But because her personality had become so fragmented, they felt external to her, but it was just her. She also had an alternative life within her brain. It was an entire world of meadows, woods, rainbows and a solid wall. Behind that wall was where she kept things--memories---pieces of herself---that couldn't function.
We had an up and down friendship. There were times I really didn't like her, because she seemed to be a different person---little did I know.
She also came across as a liar, because she would say she had night blindness, but I KNEW she always drove at night. Or she would tell me about this horrible thing someone did to her, something dangerous, and she would be terrified of this person. But the next day ask if I wanted to go to their house, and they were the best of friends. WHAT? Then it all came out. Sometimes she DID have night blindness. Sometimes bad things happened, but she didn't always remember. As I started to understand her and recognize when she switched, I picked up on other things. Once, she had this bad cold, and was quite loud about it. Coughing, sneezing, disgusting. But then her posture changed and her facial expressions. She also got quieter with her cold, and started sniffing softly every now and then and muffling coughs. I asked her how her cold was, and she said she wasn't feeling very good. Much softer.
Other than her alternative world, she would 'see' other things. When the other 'personalities' would get a bit more access, they would remember things that would intrude on her---even take over. It was very real to her, the memories, and she couldn't distinguish reality from the memories. Some of these fractured parts of her brain were very creative and even came up with false things.
Now I have to think on this for a while, Satanus. Perhaps I will even give that friend a call. She is doing better today, but the tendency is still there. One thing I remember very well, and what nearly trashed our friendship because I didn't understand, is she had severe personality changes. Sometimes she was so wonderful, kind, loving, fun, funny---and others she was hostile or bizarre. Interestingly, kind loving friend never had any memory of what hostile, bizarre friend was doing---until later. She became aware, but not always in control, so she simply had to deal with what she did, control or not---because it was all her---even if part of her did not agree with the course of action.