People who are in a vegetative state as a result of severe traumatic brain injury are in a nonresponsive state of wakeful unawareness. They are able to open their eyes and respond to some commands, but are presumed to be unaware of their surroundings and unconscious of their own thoughts and actions. However, it is not always the case that a person presumed to be in a vegetative state is completely unconscious. Case studies have found that some people are able to demonstrate awareness by using brain-computer interfaces to communicate.
There are three such non-invasive brain-computer interfaces that have shown potential for such communication. These are:
1. fMRI-which measures blood flow and has been used in experiments where patients are asked to imagine specific tasks that are associated with specific brain areas. There has been evidence of people in a vegetative state who showed the same type of brain activity associated with specific tasks as a healthy person. fMRI is the most successful of the three brain-computer technologies.
2. fNIRS-uses near-infrared light to measure brain activity. It is a safer and more accessible tool than fMRI, but also not as accurate. Early studies have shown evidence of communication in people presumed to be in a vegetative state.
3. EEG-measures electrical activity captured in time that corresponds to imagined activities. Although safe and accessible, EEG is limited in the amount of brain activity it can capture.
If a brain-computer interface captures evidence of communication in a person presumed to be in a vegetative state, that person is no longer considered to be in a vegetative state. This can affect not only diagnosis, but also treatment and ethical decisions made by both doctor and family.
Naci L, Monti MM, Cruse D, et al. Brain-computer interfaces for communication with nonresponsive patients. Annals of Neurology. (June 2012).