How conscious are people in a vegetative state? Although the answer may seem obvious, in actuality it isn’t. A recent study found that some patients who appear unconscious still have hidden brain network patterns that support a level of cognition. This indicates that even though the patients seem outwardly unresponsive, they may be aware of their surroundings and be capable of thought processing.
Studying the level of consciousness among patients in vegetative states is not a revolutionary effort. Up until this study, scientists had been using functional magnetic resonance imaging (fMRI) scanners to measure brain activity in different segments of the brain. Neural activity in the pre-motor cortex is of special concern to scientists since it is the part of the brain involved with movement. In order to determine neural activity in the patients’ pre-motor cortex, the brain capability of patients is measured after being asked to imagine playing tennis. Although this method of testing is more accurate and indicates if a patient can mentally follow commands, the technique used recently by University of Cambridge researchers can be easily administered to an admitted patient.
The combined efforts of Srivas Chennu of Cambridge’s Department of Clinical Neurosciences and his team led to this discovery. Chennu and his team used high-density electroencephalographs (EEGs) to analyze the brain signatures of 32 patients with differing levels of consciousness. The data collected was then compared with the brain network of healthy controls to identify neural activity indicative of behavioral awareness. This novel way of measuring the network mechanisms of the brain through topographical metrics makes it possible to map out specific neural signatures of consciousness. The connectivity between different bands gives specific information on the interactions between certain network modules. Now that these key patterns are identified, the researchers can detect their presence in these patients even if they do not display any external responses.
In the article, published in PLOS Computational Biology, the researchers note that complicated and diverse networks present in our brain are usually impaired in patients in vegetative states. The quality of the network connection between the different parts of the brain also directly correlates with the level of responsiveness. The presence of brain signatures in some of these patients thus indicates the possibility that some of the neural circuitry have been preserved. This means that they may possess some degree of consciousness after all.
This new take on neural circuitry through EEG and graph theory has many positive implications on future research in the state of consciousness of those in a vegetative state. It is now possible to assess the level of awareness they have of their surroundings with more accuracy – even though the patients seem unresponsive externally. The researchers think that their test could be combined with others to clinically assess the state of patients. Diagnosis of the patients could improve if doctors can more precisely determine the state of cognition in unconscious patients.
