A patient in a seemingly vegetative state - unable to move or speak - has shown signs of attentive awareness seen for the first time, Cambridge scientists say.
The patient was able to focus on words signalled by the experimenters as auditory targets as successfully as healthy individuals.
If this ability can be developed consistently in certain patients who are vegetative, it could open the door to specialised devices in the future and enable them to interact with the outside world.
Researchers at the Medical Research Council Cognition and Brain Sciences Unit (MRC CBSU) and the University of Cambridge used electroencephalography (EEG), which non-invasively measures the electrical activity over the scalp, to test 21 patients diagnosed as vegetative or minimally conscious, and eight healthy volunteers.
Participants heard a series of different words - one word a second over 90 seconds at a time - while asked to alternatingly attend to either the word 'yes' or the word 'no', each of which appeared 15 per cent of the time.
This was repeated several times over a period of 30 minutes to detect whether the patients were able to attend to the correct target word.
They found that one of the vegetative patients was able to filter out unimportant information and home in on relevant words they were being asked to pay attention to.
Using brain imaging (fMRI), the scientists also discovered that this patient could follow simple commands to imagine playing tennis.
They also found that three other minimally conscious patients reacted to novel but irrelevant words, but were unable to selectively pay attention to the target word.
These findings suggest that some patients in a vegetative or minimally conscious state might in fact be able to direct attention to the sounds in the world around them.
"Not only did we find the patient had the ability to pay attention, we also found independent evidence of their ability to follow commands - information which could enable the development of future technology to help patients in a vegetative state communicate with the outside world," said Dr Srivas Chennu at the University of Cambridge.
The study was published in the journal Neuroimage: Clinical.
