Why don't I remember conversations I've had right after waking up (and before fa!

Why don't I remember conversations I've had right after waking up (and before falling back to sleep)?

Every day my mom says that she woke me up earlier, had me sit up, and we had a whole conversation and can hardly beleive I don't remember any of it. She described what we talked about and I have no memory of it at all. She says I'm usually happy and tell her at the end that I would like to go back to sleep, and then I do. Why do I never remember this?

1 week ago
I don't think she's messing with me, SHE is the one who wants to record it. I always ask her to wake me up in the morning, and she tells me she does and tells me what we talked about for a several-minute conversation before I go back to sleep. Sometimes she says we've had three or four conversations, but the only conversation I remember is the one that I had before I finally physically got out of bed (which is usually in the afternoon).

Happens to everybody, I think.

When you're sleeping, except in REM sleep, your brain pretty much erases your memories. That's why you can't normally remember dreams very well (dreams occur in REM sleep, but you cycle through the stages so unless you wake up during REM you can't remember them very well).

You just weren't completely awake yet.