BAKERSFIELD, Calif. -- A study conducted at Cambridge University is challenging the conventional wisdom about people living in a persistent vegetative state.

These patients open their eyes and have reflexes such as yawning, but they are generally unresponsive and are not expected to get better.

But brain-scan results have showed that some patients may have a higher degree of consciousness than previously thought.

Doctors used functional MRI technology to study 54 unresponsive patients. During the scans, the researchers asked the patients to imagine certain scenarios, such as navigating the streets of a familiar town or playing tennis.

Five of the patients showed repeated, reliable brain activation that was similar to that of conscious people. Eventually one patient was even able to answer yes or no questions.

Experts said the findings highlight the difficulties in evaluating severely brain-damaged people, though including brain-scan technology in diagnosing could reduce errors in diagnoses.

But doctors also do not want to give families too much false hope -- 93 percent of the patients in this study showed no evidence of consciousness on their brain scans.