Personally, I think we need to make a distinction between whether the body is alive and whether the mind is alive. Can a person still think? If you take the brain out of the body, and it's still capable of thought, that person is still technically alive.

Think of the body as just a frame that moves your brain around. If your body can't keep your brain alive, it can be acceptable to keep the brain alive by artificial means.

But then, what separates a living brain from a conscious brain? A living brain could be capable of autonomic functions, like keeping the heart beating, but if it's not conscious, it's basically a remnant, a clock that's still ticking with nobody to check the time. To me, consciousness is what a person is above all else.

So the MRI scans that allow us to see if potentially braindead (or just locked in) people can answer yes/no questions are a big help. If a person can answer yes/no questions, they're at least somewhat conscious, capable of thought.

But then the question becomes: even if a person is conscious, how conscious are they? And just because someone is conscious, that doesn't mean they can still live a good life. The questions become about quality and potential of life. Just because someone is alive doesn't necessarily mean they need to be kept alive. In the end, the decision of whether someone should be kept alive still comes down to a decision from a person's doctor, family members, and if possible, the patient. And once again, we're back onto the subject of euthanasia.

This also demonstrates another great reason why brain research is so important. If someone is conscious but locked in, being able to hook their brains up to a computer that can allow them some control over the outside world is very important. It could be as simple as giving them the ability to answer yes/no questions, to forming sentences (like Stephen Hawking, in a way), to even being able to access information via the internet.