I remember reading/seeing some where a discussion of death and brain death and when someone is considered to be dead. The point was raised that what we think of as being 'dead' or 'brain dead' is relative, in that as technology becomes more specified and sensitive, the medical community is able to see more activity at decreased levels.
Basically, the overall idea was/is that 'dead' is a relative term and that death certificates should read something to the effect of 'Pronounced dead according the technology and accepted definitions available and in practice at this point in time.' It always bugged me to think about.
As far as someone not being able to think ... I was in a come for three days, at the age of ten, and I was thinking in there ... I was aware that something was wrong and that I was unable to wake-up. Admittedly that's not the same as someone being declared brain dead, but that's the closest that I can come to personal experience.
― I'm Passing Open Windows (Ms Laura), Tuesday, 9 September 2003 08:40 (twenty-two years ago)