Is this "dissociation"?
Every now and then, usually when hearing something or being asked to think of something that must be overwhelming for me, I have an experience that I describe as being like "a wet horsehair mattress falls on my from above and my mind shuts down". Sometimes with a slight sense of vertigo to go with it. Maybe if I were a novelist, I'd say "It made my head spin".
Whatever, the effect is that I literally cannot think about the thing - I reach for it and it slips away. I might have to ask "Sorry, say that again" before I can begin to process whatever it is, and even then, maybe it still skids out from my awareness.
Is that "dissociation"?