Brain networks in two behaviourally-similar vegetative patients (left and middle), but one of whom imagined playing tennis (middle panel), alongside a healthy adult (right panel). Credit: Srivas Chennu
People locked into a vegetative state due to disease or injury are a major mystery for medical science. Some may be fully unconscious, while others remain aware of what’s going on around them but can’t speak or move to show it. Now scientists at Cambridge have reported in journal PLOS Computational Biology on a new technique that can help identify locked-in people that can still hear and retain their consciousness.
Previously we’ve seen researchers use fMRI to recognize someone imagining playing tennis by detecting activity in the part of the brain responsible for controlling physical motion. The new research takes advantage of high-density EEG coupled with mathematical techniques from graph theory. They mapped out networks of activity within the brain and compared those with healthy individuals. Interestingly, those patients that were able to pass the imaginary tennis test also had networks that look similar to those produced by healthy brains.
Some details from the study abstract:
We devised a novel topographical metric, termed modular span, which showed that the alpha network modules in patients were also spatially circumscribed, lacking the structured long-distance interactions commonly observed in the healthy controls. Importantly however, these differences between graph-theoretic metrics were partially reversed in delta and theta band networks, which were also significantly more similar to each other in patients than controls. Going further, we found that metrics of alpha network efficiency also correlated with the degree of behavioural awareness. Intriguingly, some patients in behaviourally unresponsive vegetative states who demonstrated evidence of covert awareness with functional neuroimaging stood out from this trend: they had alpha networks that were remarkably well preserved and similar to those observed in the controls. Taken together, our findings inform current understanding of disorders of consciousness by highlighting the distinctive brain networks that characterise them. In the significant minority of vegetative patients who follow commands in neuroimaging tests, they point to putative network mechanisms that could support cognitive function and consciousness despite profound behavioural impairment.
Study in PLOS Computational Biology: Spectral Signatures of Reorganised Brain Networks in Disorders of Consciousness
Flashback: Coma Tennis…
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