Uhhhnnnhhh, Luis, here in the States "residency" IS in a specialty area, such as pediatrics, surgery, internship, etc., etc.
That includes brain surgery, although there's further training available for that particular specialty, like for certain types of coronary surgery.
Tell you what, I'll sign up to be a resident for your local hospital, and you come over so that I can do some brain surgery on you.
Is that OK with you?