A young woman apparently lost to the world after a car accident severely damaged her brain appears able to understand and respond to spoken suggestions through thought, a remarkable study has found.

Study leader Adrian Owens, a neuroscientist with the Medical Research Council Cognition and Brain Sciences Unit at Cambridge, and colleagues spoke to the 23-year old British woman, who had sustained severe brain injury in an auto accident in July 2005, and found that certain areas of her brain lit up appropriately in response to their verbal suggestions.

The team had earlier performed a series of exercises with people whose brains were normal, registering the type of activity that occurred when they were spoken to in various ways and asked to think about specific activities.

When they later performed the same exercises with the brain-injured woman, they were amazed to find that her responses matched those of the healthy test subjects.

For example, when the researchers included homonyms in their speech -- words that sound alike but have different meanings, such as "rode" and "road" -- the part of the brain that processes such language distinctions lit up in the injured woman just as it did in the healthy volunteers.

The experiment didn't end there. Owens and his colleagues found that when the woman was asked to imagine herself playing tennis, neurons fired in her premotor cortex -- the part of the brain that handles mentally practicing complex movements.

When they asked her to imagine walking through her home, the woman's parahippocampal gyrus -- the part of brain responsible for spatial mapping -- lit up. The woman's brain activity consistently matched that of the noninjured test subjects.

The results of the study are published in the journal Science.

The startling findings have sparked heated debate among philosophers, theologians, ethicists, physicians and others over what constitutes conscious awareness. Many are referencing the famous right-to-life case of Terri Schiavo, who was in a persistent vegetative state and seemingly without capacity for thought.

Despite the insistence by her parents and others that Schiavo was responsive to their speech and other stimuli, doctors maintained that her brain was incapable of conscious awareness. Following a bitter court battle and political maneuverings, her husband's decision to withdraw her food and water was allowed, which led to her death.

Medical experts are quick to point out the the two cases are very different. In fact, the woman who is the subject of the latest research may be unique among patients diagnosed as being in a vegetative state. Sixty other patients in that condition reportedly showed no similar thought activity when tested.

Scientists are at a loss to explain why the woman shows brain activity consistent with conscious awareness yet is unable to move or speak, since the parts of her brain governing those functions are unimpaired.

Unlike being in a coma, a person who is in a vegetative state displays some signs of brain function, which may include breathing, opening eyes, sleeping and waking during regular cycles, and even laughing or crying. However, they do not appear capable of intelligent thought or of relating to the world in any meaningful way.

Initially, the woman in the latest case had been in a deep coma following her car accident. After some time, she opened her eyes and began to go through regular cycles of sleeping and waking, but she showed no signs of conscious awareness.