British scientists are reporting new information that could raise hopes for families of people in what are called "persistent vegetative states." Not only are some of those patients aware, but they may also be paying attention to what is happening around them, say researchers from the Medical Research Council and the University of Cambridge.
Although patients in such states are unable to speak or move, measurements of brain activity reveal surprising signs of attention and awareness that have not been detected before, according to the study published in the journal Neuroimage: Clinical.
The research raises the hope that medical devices in the future may be able to help some patients in a vegetative state interact with the people 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 Srivas Chennu, a Cambridge specialist who helped conduct the research.
"In order to try and assess the true level of brain function and awareness that survives in the vegetative and minimally conscious states, we are progressively building up a fuller picture of the sensory, perceptual, and cognitive abilities in patients. This study has added a key piece to that puzzle, and provided a tremendous amount of insight into the ability of these patients to pay attention."
For the study, the researchers used electroencephalography (EEG), which 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 words — one word a second over 90 seconds at a time — while asked to pay particular attention to the words "yes" and "no," which appeared periodically.
The goal of the experiment was to detect whether the patients were able to focus attention on the correct target word.
They found that one of the vegetative patients was able to home in on relevant words as successfully as healthy people. Using brain imaging, the scientists also discovered that this patient could follow simple commands to imagine playing tennis. In addition, three other minimally conscious patients reacted to novel but irrelevant words, but were unable to selectively pay attention to the target word.
The findings suggest that some patients in such states might in fact be able to direct attention to the sounds in the world around them.
"Our attention can be drawn to something by its strangeness or novelty, or we can consciously decide to pay attention to it. A lot of cognitive neuroscience research tells us that we have distinct patterns in the brain for both forms of attention, which we can measure even when the individual is unable to speak," said Tristan Bekinschtein, M.D., with the MRC Cognition and Brain Sciences Unit.
"These findings mean that, in certain cases of individuals who are vegetative, we might be able to enhance this ability and improve their level of communication with the outside world."
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