Researchers from the Medical Research Council Cognition and Brain Sciences Unit (MRC CBSU) and the University of Cambridge analyzed the brain activity 21 patients and eight healthy volunteers. The scientists used electroencephalography (EEG), which non-invasively measures the electrical activity over the scalp. The analysis showed one of the patients could pick out individual sounds. The researchers believe the finding marks an advance in understanding the levels of consciousness in vegetative patients and minimally conscious patients, and they hope to develop better ways for some patients to communicate. The research is published in the journal Neuroimage: Clinical.
There are three main states of impaired consciousness. A coma is where there are no signs of wakefulness or awareness, a vegetative state is where a person is awake but showing no signs of awareness and a minimally conscious state is where there is clear but minimal evidence of awareness that comes and goes. Both vegetative and minimally conscious states can leave people with no higher cognitive function. This trauma can be caused by traumatic brain injuries such as a car accident, or by non-traumatic brain injuries such as a stroke. Progressive brain injuries where the brain is gradually damaged over time can also cause someone to enter a minimally conscious state. Patients in a vegetative or minimally conscious state may still be able to move their eyes and limbs but cannot do so on command.
During the experiment, the patients and volunteers had their brains scanned. All participants were played a word every second for 90 seconds and were told to count the number of times the word "yes" or "no" appeared during the stream of words. The brainwave records showed that one patient’s brain activity was "indistinguishable" from the healthy patients, which suggested he was able to focus his attention on the words. While three other patients showed some brain response, theirs was thought to be an involuntary action. All other patients showed no response.
The aim of the study was to change the way patients were treated, to match their level of consciousness. While Dr Srivas Chennu admits they can never fix the patients, the team want to get doctors having the best information to make decisions for the patient. This could include communication with the patient, where possible.
The researchers hope that if this ability can be developed consistently in certain patients who are vegetative, it could open the door to specialized devices in the future and enable them to interact with the outside world.