Persistent vegetative state (PVS) is considered the most extreme state of brain injury, short of brain death. The conventional thinking in the medical community has been that people in PVS were mindless shells—a body without a mind. That’s what “vegetative” means.

But in 2006 neuroscientist Adrian Owen and his Cambridge team published a landmark paper in Science titled “Detecting awareness in the vegetative state.” Owen reported the case of a young woman who was in PVS for several years due to an automobile accident.

Like other patients in PVS, the woman did not respond to her environment in any conscious manner. She did not speak, respond to requests or purposefully use her limbs.

Owen recognized that her massive brain damage not only affected her mind, but also her ability to move and interact. So he wondered, if she couldn’t communicate how could he know for sure that she had no mind?

To try to find out, he put her in a magnetic resonance imaging machine for a test called functional MRI (fMRI) imaging. The MRI detects local changes in blood flow in the brain that often correlate with brain activity and various mental states.

While she was in the machine, he asked her to think about things— things like playing tennis or walking across the room. Remarkably, blood vessels in areas of her nearly destroyed brain lit up, which suggested that she might be aware of his question and thinking about it. Wanting to be sure, he did fMRI imaging on normal volunteers, asking the same questions. And they had identical fMRI responses!

To be sure that the patient was really responding and thinking, he took the test a step further. He asked her to do the same things, except that he scrambled the words so his requests no longer made sense. Her brain was silent. That implied that she genuinely understood what he had asked her the first time. So her initial response wasn’t just due to brain activation by the sound of his voice. She had understood.

Since Owen’s pioneering work, many other neuroscientists have tested people in PVS for evidence of mental states. A 2015 review of their studies revealed that 37% to 43% of patients diagnosed in PVS have preserved awareness by various clinical tests. One result of this work is that a new diagnostic category was created for those who were not able to interact but were quite aware of their surroundings— the minimally conscious state.

What it means for the mind vs. the brain

These cases are important and fascinating for two reasons: They tell us that we should care for people in PVS compassionately and assume that they are to some extent aware. But they also tell us important things about the mind‒brain connection.

Attempting to account for the way that relatively sophisticated mental states are preserved in patients with the most severe brain injuries, many of my colleagues have suggested that the brain injury probably didn’t destroy isolated areas of the brain (like areas of the cortex) that mediate awareness and thought. This may be true to some extent but it seems ad hoc. It is the materialist view of the mind‒brain connection: the mind is wholly the product of brain activity, and any preserved mind activity must be caused by preserved brain activity.

The dualist view of the mind‒brain connection— which is my view— is that brain activity is necessary for much normal mind activity. But for some kinds of mind activity— such as intellect and will— brain activity is not sufficient. The dualist view is that there are aspects of the mind that are not generated entirely by the brain.

So which perspective— the materialist or the dualist— does the research with PVS patients support? It is true that mind activity in these patients is detected materially— by fMRI imaging of brain blood flow.

But we should note that all mind activity that we detect in other people is detected by their behavior—we always use material methods (mannerisms, speech, writing, etc.) to discern what other people are thinking. But it does not follow that all thinking is generated by brain matter— it merely means that all communication depends on material expressions.

The best way to test scientific hypotheses is to compare the predictions they make. The materialist hypothesis— that all mind activity is brain activity of one sort or another— predicts two things: that massive brain damage would extinguish or nearly extinguish all mind activity, and that there would be a consistent proportionality between brain damage and mind damage. The dualist hypothesis— that some mind activity is independent from brain activity— predicts that massive brain damage would not extinguish all mind activity. Thus there might not be a consistent proportionality between brain damage and mind damage.

The materialist paradigm is challenged by awareness in PVS. The dualist perspective better fits the evidence. None of this research is decisive, but the results so far clearly support the dualist perspective that there is at least one aspect of the mind that is independent of the brain.