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Study by Cambridge researchers finds ‘hidden brain signatures’ of consciousness in patients said to be in a persistent vegetative state

by | Oct 21, 2014


By Dave Andrusko

BrainnetworksLast week the UK Independent newspaper published an article written by Science Editor Steve Connor, exploring a fascinating study by scientists at Cambridge University which found “Severely brain-damaged patients in a persistent vegetative state may be capable of being consciously aware of the outside world.” It is the latest in many experiments that strongly suggest we don’t know nearly as much as we think we do about the interior life of many patients said to be in a PVS.

According to Connor,

“The study, published in the online journal Plos Computational Biology, found that four of the 13 patients with persistent vegetative state had a ‘robust’ network of brain activity that would allow conscious thoughts, which was confirmed when they were asked to imagine playing tennis when their brains were scanned using a magnetic resonance imagining (MRI) machine.”

{The study, “Spectral Signatures of Reorganised Brain Networks in Disorders of Consciousness,” is online}

Dr. Srivas Chennu, a clinical neuroscientist at Cambridge University, told Connor that the relatively simple test could be developed into a diagnostic tool for doctors.

“Understanding how consciousness arises from the interactions between networks of brain regions is an elusive but fascinating scientific question,” he said. “But for patients diagnosed as vegetative and minimally conscious and their families, this is far more than just an academic question; it takes on a very real significance.”

Typically, in the brains of healthy people, there are “rich and diversely connected networks” of brain activity that is lacking in the brains of patients with severe brain damage.

Using EEG, researchers analyzed the brainwaves of 32 patients, 13 of whom were classed as being in a persistent vegetative state. The remaining 19 were classified as being “minimally conscious.” All were compared with 26 healthy subjects.

What did they find? According to Connor, of the 13, four had what Chennu et al. described as a “robust” network of brain activity that would allow conscious thoughts. But what does that mean?

I went to an article in Science Codex for further detail.

“The researchers showed that the rich and diversely connected networks that support awareness in the healthy brain [what Science Codex called ‘hidden signatures’] are typically – but importantly, not always – impaired in patients in a vegetative state.”

This technique can serve as a complementary way of finding out which patients who cannot communicate are nonetheless aware. The other most prominent technique is one we’ve written about before at NRL News Today.

Patients are asked to imagine playing tennis while their brains are scanned using a functional magnetic resonance imagining (fMRI) machine. If certain parts of the brain (the pre-motor cortex) fire up the way they did in healthy control subjects, they could deduce that they were conscious.

According to Science Codex

“The findings could help researchers develop a relatively simple way of identifying which patients might be aware whilst in a vegetative state. Unlike the ‘tennis test’, which can be a difficult task for patients and requires expensive and often unavailable fMRI scanners, this new technique uses EEG and could therefore be administered at a patient’s bedside. However, the tennis test is stronger evidence that the patient is indeed conscious, to the extent that they can follow commands using their thoughts. The researchers believe that a combination of such tests could help improve accuracy in the prognosis for a patient.”

According to Dr. Chennu,

“Our research could improve clinical assessment and help identify patients who might be covertly aware despite being uncommunicative.”

Categories: PVS