Want to build a robot, need help!

[defau...@domain.com]

Hi all,
My aim would be on the brain, instead of its motion ( I want it
just look like a robot, so it doesn't have to be movable).
I want to "show some interaction between human and robot", like
receiving my voice and let it do some response to show that it got the
message (maybe a flash or beep.)
So, my problem is, "what stuff could make up its brain?"
Microprocessors? or?
I would be very thankful to any suggestions !