Signs of consciousness have been detected in three people previously thought to be in a vegetative state, with the help of a cheap, portable device that can be used at the bedside.
鈥淭here鈥檚 a man here who technically meets all the internationally agreed criteria for being in a vegetative state, yet he can generate 200 responses [to direct commands] with his brain,鈥� says of the University of Western Ontario. 鈥淐learly this guy is not in a true vegetative state. He鈥檚 probably as conscious as you or I are.鈥�
In 2005, Owen鈥檚 team, used functional MRI to show consciousness in a person who was in a persistent vegetative state, also known as wakeful unconsciousness 鈥� where the body still functions but the mind is unresponsive 鈥� for the first time. However, fMRI is costly and time-consuming, so his team set about searching for simple and cost-effective solutions for making bedside diagnoses of PVS. Now, they have devised a test that uses the relatively inexpensive and widely available (EEG).
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An EEG uses electrodes attached to the scalp to record electrical activity in the brain.
Imagine wiggling your toes
Owen and his team used an EEG on 16 people thought to be in a PVS and compared the results with 12 healthy controls while they were asked to imagine performing a series of tasks.
Each person was asked to imagine at least four separate actions 鈥� either clenching their right fist or wiggling their toes.
In three of the people with PVS, brain regions known to be associated with those tasks lit up with activity, despite physical unresponsiveness. This suggested to the researchers that the subjects were carrying out a complex set of cognitive functions including hearing the command, understanding language, sustaining attention and tapping into working memory.
鈥淚t isn鈥檛 the case that just because somebody doesn鈥檛 respond they鈥檙e not conscious,鈥� Owen says. 鈥淭here鈥檚 a growing body of data now demonstrating that many of these patients aren鈥檛 what they appear.鈥�
鈥淭he diagnostic criteria for vegetative state have to change,鈥� he adds. The official diagnosis for PVS was formulated in the 1970s, before neuro-imaging was widely used, says Owen. The last update was made in 1995, but the criteria for declaring someone conscious is still based on whether an outside observer believes the patient is trying to communicate.
Morten Overgaard, a cognitive neuroscientist at Aalborg and Aarhus University in Denmark, says that determining whether Owen鈥檚 patients are actually responding consciously or whether they are unconsciously reacting to suggestions from the command is difficult to know without further study.
鈥淚f this is suggested as a standalone test to decide whether a person is conscious or not, then we need [signs] that are very strong and not just an indication of consciousness,鈥� he says.
The test cannot prove the absence of awareness, but it can identify people who weren鈥檛 thought to be conscious, says Damian Cruse, a collaborator on the study. This was particularly apparent when 25 per cent of the healthy controls returned EEG readings that were below expected levels of conscious thought.
However, for those people previously considered to be unaware of their surroundings, communicating with their caretakers through EEG tests could change their life. 鈥淲e鈥檙e trying to work out how to use this technique to find out more about somebody鈥檚 internal mental state,鈥� says Owen. 鈥淚t opens up the possibilities for potentially facilitating recovery. If you have a channel of communication with a patient, you can have that patient play a role in therapeutic intervention.鈥�
Using EEG to ask questions of these patients is the next step. By assigning thought processes to simple answers 鈥� for example, imagining clenching a fist means 鈥測es鈥� and wiggling toes means 鈥渘o鈥� 鈥� the team hopes their work can result in better clinical treatment. 鈥淭here are some interesting questions that one should get on to right away,鈥� Owen says. 鈥淥ne is, 鈥楢re you in pain?'鈥�
Owen says the ultimate goal is to equip these people with a constant means of communication. For example, brain-computer interfaces that allow a person to control a mouse cursor with only their thoughts could be combined with further research into the mental capabilities of people with PVS.
鈥淎ll of the technical and scientific building blocks are in place,鈥� he says. 鈥淭he future for us is to put these together.鈥�
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