It was 4 out of 23 vegetative patients studied who responded to the stimuli and the scientists seemed quite cautious about the results.
Don't know if it was in this summary of the study or another one I read which stated that patients who responded had experienced traumatic brain injury whereas people with brains damaged from lack of oxygen did not respond.
Seems to me that a person has to be pretty aware to respond to a command to play tennis in his head and then actually carry it out. I can't imagine a much more hellish existence that what those people are experiencing if the study turns out to be accurate. I wonder if they asked the patients if they were capable of experiencing pain?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13