Consequently, for several years now, the focus has been on designing tools that are sensitive, inexpensive and easy to use. A great deal of work has been done in this area, in particular, based on electroencephalography (EEG) and cognitive event-related potentials. The Coma Science Group has taken part in various projects of this type, with a focus on brain-computer interfaces (BCIs). One of the most successful of these is the subject of Damien Lesenfants’ recent doctoral thesis.

As he points out, the goal was to “use the technology of brain-computer interfaces in order to develop a diagnostic tool independent from the motor test, leading to an objective assessment of the response to a command in patients suffering from locked-in syndrome and disorders of consciousness”. An additional objective was to establish communication with conscious patients through the interface.

In 2006, as you may well remember, researchers from the University of Liège and Cambridge were the first to successfully communicate with a severely brain-injured person who was supposedly unconscious according to behavioural tests. They managed to decipher the (positive or negative) responses to basic questions, based on the recording of brain activity in a patient wrongly diagnosed as being in a vegetative state. The interface used was real time fMRI. The patient’s brain activity was recorded while they were supposed to be imagining themselves playing tennis if they wanted to answer “yes” to a question, or wandering through their house if they wanted to answer “no”.  The researchers then successfully repeated this experiment on other patients.

Overt or covert

Being able to determine residual consciousness in every severely brain-injured patient is essential both on a medical and ethical level. Subsequently, the prognosis (chances of recovery) and the various rehabilitation techniques will differ depending on whether a patient is in a vegetative / unresponsive state, a minimally conscious state or has locked-in syndrome. The medical treatment is also different, insofar as patients in a minimally conscious state feel physical pain – and have to be given painkillers in some cases -, contrary to their counterparts in a vegetative / unresponsive state. And, finally, there is the painful issue of the end-of-life decision. “When there are signs of consciousness, it is vital to try and establish a dialogue with the patient concerned in order to allow them to express their feelings, needs (are they suffering?) and desires, especially regarding end-of-life decisions”, Steven Laureys adds.

Several methods were suggested as a medium for the brain-computer interfaces. For instance, motor evoked potentials. Damien Lesenfants opted for the Steady-State Visually Evoked Potentials (SSVEP). What are their advantages? The low influence of muscular and ocular artefacts and movements; the reduction in the duration of the examination, since it doesn’t require the user to have any training; a high signal/noise ratio and information transfer rate.

“In SSVEP-BCIs, one or more stimuli oscillating at constant and different frequencies are presented to the user”, explains Damien Lesenfants in his thesis. “When the latter focuses their attention on a stimulus, an increase in EEG activity at the frequency of the stimulus is detected in the posterior regions of the brain, particularly in the occipital areas”.