This breaks my heart because I've been there with my son Eric who was born with a condition of dwarfism that is always fatal. He lived for 100 days but when I asked the medical folks about his consciousness, his brain, his development, etc., there was no information. Zilch. All there was on such babies was diagnosis in the womb or at birth and post-mortem autopsy information.
Some people viewed him as a "vegetable" (an actual word one doctor used about an older surviving child with his condition). Others, who hung out with him, discovered responsiveness and receptivity. In Eric's case, I had a developmental specialist assess him once a week. Later, I put that information into an article for Delaware Medical Journal. Mine was the first article on thanatophoric dysplasia that tracked the development of these babies "born to die" while they were still alive.
I trust the folks who perceive responsiveness in Terri Schiavo more than I trust those who do not. My own experience shows me that medical professionals are just as prone to allow their own prejudices about the meaning of life in its extremes to affect their judgment as anyone else.