Three brain injury patients diagnosed as being in a vegetative state—meaning they do not respond to their environment—may actually be conscious. Using EEG (electroencephalography) to measure their brain activity, researchers found that the patients could follow simple commands.
This supports previous findings from the same group suggesting that some people who appear outwardly unresponsive may have a relatively high level of cognitive capacity. Researchers aim to ultimately develop the approach into a communication tool.
In the study, researchers examined 16 patients with brain injury—some due to traumatic injury and others due to lack of oxygen—and 12 healthy people, asking both groups to imagine moving either their hands or toes while wearing an EEG monitor. They found that, like the healthy people, three of the brain injury patients could reliably generate two distinct brain activity patterns based on the command. One patient did it more than 200 times, which is even more than the healthy participants managed.
The team had previously used functional MRI, or brain imaging, to show that a patient diagnosed as being in a vegetative state could use a similar system to answer yes or no questions. That startling finding rocked the medical world, begging the question of how many of these patients had cognitive function beyond what their outward function indicated.
MRI machines are, however, expensive and largely limited to hospitals, making them a difficult tool to study brain injury patients, who are often in rehabilitation or nursing homes. In the new study, researchers used a standard EEG device, which is relatively inexpensive and highly portable. “It’s probably about as sensitive as MRI,” says Adrian Owen, a researcher at the University of Western Ontario, who led the study. “That means we have something we can get out into the community and use in hospitals or residential homes.”
The researchers can detect when someone is thinking about moving a hand versus a toe because the brain activity originates in a different part of the motor cortex, the part of the brain that controls movement. Owen’s team spent much of the last year working out how to accurately decode the electrical signals the brain emits when imaging these movements. The findings of the new study were published this week in The Lancet.