Conditional Consciousness; December 2009; Scientific American Magazine; by Katherine Harmon; 2 Page(s)

In patients who have survived severe brain damage, judging the level of actual awareness has proved a difficult process. And the prognosis can sometimes mean the difference between life and death. New research suggests that some vegetative patients are capable of simple learning—a sign of consciousness in many who had failed other traditional cognitive tests.

To determine whether patients are in a minimally conscious state (in which there is some evidence of perception or intentional movement) or have sunk into a vegetative state (in which neither exists), doctors have traditionally used a battery of tests and observations. Many of them require some subjective interpretation, such as deciding whether a patient's movements are purposeful or just random. "We want to have an objective way of knowing whether the other person has consciousness or not," says Mariano Sigman, who directs the Integrative Neuroscience Laboratory at the University of Buenos Aires.