Your brain wouldn't be worth much without your body. You'd be surprised how much your body does. Think of typing for example. You couldn't do it without the exact nerve/muscle pathways in your hands. Hook up robot hands (even crudely modelled after your existing nervous/muscle/bone system in your current hands) and you'd basically have to relearn to do anything. You'd be a baby again.

I think you'd be surprised how much this applies to. Speech, even things like counting we rely on our bodies for.