theoretical brain implant?

i was thinking about this today. i know i probably wont see it in my lifetime and people might never but theoretically would it be possible to create a device that would be implanted into your brain and alters the brain signals. like you plug a wire from your head to a super computer and it tells your brain to see and feel something else? so you would be in like another world and it would feel real but you would know its not? could this actually work? it would be like xbox 9,999,999,999