A SIMPLE bedside scan could reveal an active mind hidden inside an unresponsive body. The method provides another tool for recognising consciousness in people who have been wrongly diagnosed as being in a vegetative state. Tests are also under way to use it to monitor people under general anaesthetic, to make sure they do not regain consciousness during an operation.
The technique builds on recent research into the nature of consciousness. “Information that is processed consciously typically recruits several brain regions at once,” says Jean-Rémi King at the Brain and Spine Institute (ICM) in Paris, France. Other information that enters the brain triggers unconscious activity – for instance, the righting reflex that helps us retain balance when we are pushed – and it only tends to activate one brain area.
King and his colleague Jacobo Sitt, also at the ICM, reasoned that they could spot consciousness in people simply by playing them a series of beeps and then searching electroencephalogram (EEG) brain scan data for evidence that signals from different brain regions fluctuated in the same way as each other, suggesting that they were sharing information.
They performed their tests on 75 people in a vegetative state, 67 minimally conscious people, 24 people who had recently regained consciousness after a coma, and 14 healthy controls. By running the EEG data through statistics software, the researchers found differences between the patterns from people who were fully conscious, those in a vegetative state, and those who were minimally conscious (Current Biology, doi.org/n42).
“This adds another string to our bow of diagnostic tools that we can use to identify those patients who are aware, but unable to show it with their bodies,” says Damian Cruse of Western University in London, Ontario, Canada.
Cruse and his colleague, Adrian Owen, have recently begun communicating with such people by asking them questions while monitoring neural activity.
The technique developed by King and Sitt could work in situations where Cruse and Owen’s methods cannot, because, as Cruse points out, it works even on people whose injuries prevent them from imagining responses to questions. “They simply listen to a series of beeps, and their brain does the rest,” says Cruse.
Even listening might be unnecessary for the technique to work, says King. “The recording should probably even work without any external stimuli – although this still needs to be tested,” he says.
That might make the approach particularly suitable for ensuring that people stay unconscious during operations. King and Sitt are now looking to adapt their method for constant monitoring of anaesthetised patients. Around 1 in every 500 people recovers some awareness while still under the knife, so having a reliable consciousness measure during surgery is important, says Sitt.
This article appeared in print under the headline “Locating life’s spark in coma brains”
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