A new technique could measure the level of consciousness a person with severe brain damage is able to experience.
The Perturbational Complexity Index (PCI) measures the brain's response to a magnetic pulse, LiveScience reported.
Scientist's warned the process should not be used to determine whether or not to keep a patient on life support, but rather to monitor a patient's recovery.
A person's appearance can be deceiving, people can be in a "locked-in" state where they are fully conscious by unable to move or respond and others can be in a vegetative state but still move their faces and bodies. This new process could help distinguish between the two.
The technique started with the idea that "consciousness depends on the brain's ability to coordinate information across interacting regions, LiveScience reported. When the magnetic wave passes through these different regions it can determine the activity pattern created.
A conscious part of the brain will give off a full electroencephalography (EEG) signal when monitored, unconscious areas will have a much shorter response.
Researchers tested the technique on 52 patients in various stages of sleep or with different levels of brain damage.
The PCI was able to distinguish between these different stages of brain function.
Patients' consciousness was rated on a scale of zero to one.
"Fully awake patients in the study had a PCI of 0.6 or higher, patients in a dreaming (light) sleep had a PCI of about 0.4 and patients in a deep sleep had a PCI of about 0.2. Those who were anesthetized had PCIs as low as 0.12, which means they were in a deep state of unconsciousness. The more potent the anesthesia, the lower the PCI," LiveScience reported.
Patients suffering from "locked-in syndrome" had PCIs of about 0.6 and those in a "minimally conscious state" were at about 0.3.
Study leader Dr. Marcello Massimini of the University of Milan said the technique cannot be used to measure "absolute consciousness."
"No objective measure can be used to rule out the presence of consciousness, because we do not have a clear understanding of what are the physical properties that are necessary and sufficient for subjective experience," he said. "When measuring consciousness, it is safe to say that the absence of the proof is not proof of the absence," Massimini told LiveScience.
