This Report from the Dallas Morning News shines new light in the grey area of what doctors have called the "permanent vegetative state". A woman who was in a coma was placed in a scanner and then asked to imagine herself playing tennis, or walking around her house. In both cases her brain lit up with activity, just as it might had she been conscious.
So much for the notion that people who are in comas are unaware of what is happening around them. This is especially so for those in permanent vegetative states. While the article says that one instance is not cause to make sweeping judgements, there should be more study.
I think that it is sad that testing like this comes too late to have helped keep someone like Terry Schindler Shiavo alive. Perhaps had they been able to prove to someone that she was aware and that her brain could respond to commands even if her body couldn't, she might still be alive today even if her husband wanted her dead.
We can never know. We can only hope that this new information will help keep someone else alive in the future.