Scientists find signs of brain activity in previously unresponsive patients

Scientists have found that looking at EEG brain scans in a new way shows signs of consciousness in some patients assumed to be in a vegetative state.

As Wired reports, a new study from the University of Cambridge used EEG electrodes to measure resting brain activity in 32 severely brain-injured patients, which they compared to a control group of 26 healthy adults. Using graph theory, they analysed the strength and location of the signals they picked up.

Patients in a vegetative state show no outward signs of consciousness, and most of the patients in the study had brain activity that confirmed they had no awareness of their surroundings. However, to the researchers’ surprise, three of the patients’ EEG readings were very similar to those of the healthy adults. (The middle scan above is one of these, compared to a healthy adult on the right, and an unresponsive patient on the left.) These patients all also passed the ‘tennis test’.

This method of analysing brain activity involves taking fMRI scans of patients (using an MRI scanner to measure blood flow in the brain) while asking them to imagine playing tennis. This stimulates the part of the brain that controls movement in healthy patients. A 2006 study found that it also provoked similar activity in the brain of a 23 year-old woman who was otherwise unresponsive, suggesting that some patients in a vegetative state are still aware of language and at least some of the world around them, even when they’re unable to move or communicate.

EEG scans are easier to administer than MRIs, but Srivas Chennu, who led the study, said that both tests could be useful in determining the level of activity in patients with brain injuries in future. The scientists, who presented their findings in PLOS Computational Biology, hope that their research will help medical staff and families to understand which patients are unlikely to get better and, more optimistically, to identify those with the best chances of recovery.

Image credit: Srivas Chennu.

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