>>/45728/
> I thought all processes are handled by the whole brain 
Some parts are responsible for specific functions. These parts can indeed work together (e.g. vision - frontal parts, occipital zones, parts of midbrain - they work together, but each part is responsible for its own function).
Many people with strokes can't recover - they can lose vision, ability to walk, fine motor skills etc
Also great example is lobotomy. 
So it depends on injury.