What is consciousness? While philosophers, poets, scientists, and the occasional accountant have grappled with this question, for the families of patients in a vegetative or minimally conscious state, “this is far more than just an academic question — it takes on a very real significance,” said Dr. Srivas Chennu, Department of Clinical Neurosciences at the University of Cambridge.
In a recent study, he and his co-researchers investigated the brains of people in a vegetative state and compared them to those of healthy volunteers. They discovered in a minority of the patients, the distinctive brain networks that support cognitive function and consciousness appeared to be undamaged — even though the patient was unmoving and unresponsive. “Our research could … help identify patients who might be covertly aware despite being uncommunicative,” Chennu said.
Are patients in a vegetative state aware of their surroundings? Past scientific research provides some intriguing, if inconclusive, evidence. For instance, although unable to move or respond, some coma patients have shown they are capable of imagining themselves playing a game of tennis. Most surprising of all, using an fMRI scanner researchers have recorded activity in their pre-motor cortex, the part of the brain which deals with movement. These results have intrigued and inspired many scientists, who have devised different experiments and tests to further explore the capabilities of coma patients.
In his current study, Chennu and collaborating scientists used high-density electroencephalographs (EEG) in addition to a branch of mathematics known as graph theory to study networks of activity in the brains of 32 patients diagnosed as vegetative and minimally conscious and then compare them to healthy adults. They observed rich and diversely connected networks to support awareness in the healthy brain, while for most patients in a vegetative state, these same networks were impaired. However, some vegetative patients had well-preserved brain networks that look similar to those of healthy adults.
According to the team, their findings could help researchers develop simple ways of identifying which vegetative state patients might be aware, though they caution it would take more, a whole combination of tests, in fact, to improve the accuracy of a patient’s prognosis. Still, the results of the current study provide an important key: If patients’ awareness networks are intact, then in all likelihood they may be aware of most or even all of what is going on around them.
Source: Chennu S, Finoia P, Kamau E, et al. Spectral Signatures of Reorganised Brain Networks in Disorders of Consciousness. PLOS Computational Biology. 2014.