Say someone had an irreversible brain problem, and brain transplants had become possible... how much of the original person would actually remain if the procedure were carried out?
Just an odd question that came to me whilst reading an article about organ transplants...
I think the person is the soul, not the brain. So 100%
Science disagrees with you.
What you're saying is that if someone shoots you in the head, turning your brain into goo, your body is kept alive, and someone takes another person's brain and puts it in your skull that YOU would be alive and that that other person would cease to exsist?
Sorry, you're wrong.
MRIs, CAT scans, PET scans and any other scan/test done on the brain shows time and time again without fail that the brain contains everything that we are and know. No information is stored in any other part of the body. (Accounts of people "claiming" to develop tastes or traits of organ donors are likely suffering from a form of self-fulfilling beliefs.)
If your brain dies you go with it.Want to believe in souls? Fine, the soul lives in the brain and not the whole body. If all your body "needed to be you" was the soul then hypoxic brain injury and other severe brain maladies would be non-exsistant.
Put my brain in another's body? I would become that other person (a hot red-headed woman, please.

) and that other person would be gone (unless their brain is put in another's body.)
There's no reason at all to believe that without the brain in your head right now that there'd been any "you" to exsist.