Really the only thing in my head is my internal monologue. If I'm thinking about something I've seen, it's my internal monologue "saying," with words, physical attributes I remember about it. If a song is stuck in my head, it's my internal monologue (in my own voice) signing the lyrics or my own voice humming the tune in my head. No sensation of it being the original artist or the actual instruments, it's 100% my own voice in my own head.
I have a friend who says she does not have any inner monologue at all, and thinks entirely visually. I can't imagine! We're on the pretty extreme opposite ends of the spectrum of how we think, apparently.
I still remember (semantically) that my parents laughed at me, when they told me to count sheep to fall asleep and I told them all I can see is darkness and white dots when I close my eyes. They probably thought I was joking.
* presence of internal monologue
* ability for visualization
* ability for audiation
* affective memory (remembering feelings)
* SDAM (weak autobiographical memory)
It speaks to the larger questions around the human experience, and that we are only now discovering the many ways it differs for each individual.