Then last year, Borjigin turned to Mashour, a colleague with expertise in EEG and consciousness, for help conducting the first experiment to systematically investigate the brain after cardiac arrest. EEG uses electrodes to measure voltage fluctuations in the brain caused by many neurons firing at once. A normal, awake brain should show spikes depending on what types of processing are going on; in a completely dead brain, it flat-lines.

When the heart suddenly stops, blood flow to the brain stops and causes death in a human within minutes. A likely assumption would be that, without a fresh supply of oxygen, any sort of brain activity would go flat. But after the rats went into cardiac arrest, Mashour and his colleagues observed the opposite happening.

“We saw a window of activity with certain signatures typically associated with conscious processing,” he said.

Those signatures include heightened communication among the different parts of the brain, actively seen in an awake state. Mashour speculates this could be a marker of consciousness — in which the brain integrates disparate aspects of the world, like visual in one area and auditory in another.