Some persons with AS has concentration issues. I am one of those and for me it's like I concentrate so much on what I'm doing/thinking so that I block other input.
It happens often when I'm in a conversation that I gather keys of what the conversation is about and when I think it's appropriate I say something relevant, only to find out that the other person already said that earlier but in different words.
When I try to get work done I need to be alone in the room and usually turn on music so that I can't hear people around me, just so that I can concentrate on the work. If someone require my attention I don't get anything done, neither my work nor what the other person wants me to do.
I don't know if we have the same issue, but know that some AS persons have issues with concentration. You can always say "Shut up and wait a second!"