US researchers have measured what happens when unconscious people are 'unplugged' from resuscitation machines after massive heart attacks. Two patients showed a surge in brainwaves.
What happens in those last moments when we pass from life to death? According to the accounts of many people who recovered after their heartbeat stopped (i.e. who have had a near-death experience), we relive certain moments of our lives, re-experience crucial situations, or we have a feeling of being in the dark, but see a light at the end of this darkness. Of course, we need to be very careful when we evaluate these kinds of statements.
In order to better understand what these experiences (which have common features and have been known for a very long time) mean, neuroscientists at the Michigan Center for Consciousness Science (USA) set up a unique experiment with the cooperation of the intensive care unit of the local hospital. As reported in the scientific journal PNAS, the team chose four patients who were completely unconscious after severe cardiac arrests. These people were only kept alive by resuscitation machines. After medical and technical tests that proved - at least according to current parameters – that there was no possibility of recovery, the four patients were taken off life support, with the consent of their families.
However, removing the pulmonary ventilation equipment and subsequent death caused two of the patients, who were being monitored by EEGs and other instruments, to experience an increase in heart rate associated with an increase in the amplitude of EEG gamma waves, i.e., the part of the circuit that is associated with consciousness. These surges occurred precisely in the area that neurologists call the hotspot of consciousness, the intersection between the temporal, parietal and occipital lobes at the back of the brain, which is already known to be activated during dreams, hallucinations, epileptic fits or various states of altered consciousness.
The two patients had a history of epileptic seizures but did not have one at the time. The other two patients died without showing any signs of cardiac or cerebral activity.
Of course, we will never know whether or not those spikes in brain activity, triggered by the sudden and complete absence of oxygen (and thus death), were coupled with an experience similar to those described of reliving a few moments of their lives, or a light at the end of the tunnel. And of course, two cases alone have no statistical value.
However, what was recorded calls into question the parameters that normally define a state of brain death and point to the possibility (at least in certain circumstances) of some activity in the nervous system and consciousness. This is also similar to what has been recorded over the last decade in animal testing. 'Our data,' the University of Michigan researchers write in PNAS, 'shows that a dying brain may still be active, and suggests that we need to reassess the brain’s role during cardiac arrest.
This study also relates to another story that caused surprise and debate among scientists: the sudden death of a patient while an electroencephalogram was in progress (The brain lives on for 30 seconds after death). Also in this case, unexpected brain activity was recorded at the moment of death, and up to 30 seconds afterwards.