"There are probably a very small number of patients who are in this minimally conscious state. The exciting thing is, is that maybe there's a potential for rehabilitation," said Vespa.
Researchers, like Laureys, will have to do more work to define which brain image results from a functional MRI or PET machine are signs of a response, and which are random noises, before such progress could happen.
"We're not at the point where you can just throw somebody in the scanner and come up with the answer," DeGeorgia said. "[We] don't know how to interpret these [scans], because there have only been a few studies, and you have to know what is normal, and what is within the bell-shaped curve."
ABC News' Christophe Schpoliansky contributed to this report.