Yes, generally. Although I'm sure you're aware of some brains preserved in jars, for example. That is, you appreciate that a brain can be removed from a skull. And specifically, you don't know that your brain resides in a skull. You assume it does, but you don't know. To keep things simple for now, perhaps you'd better concentrate on the example of a physical brain as you know it in a physical vat somewhere. Once you've got that scenario straight in your head, then we can move on to discuss simulated brains in computers or something.