The many experiences described by survivors of cardiac arrest — people revived even after their hearts stopped beating, sometimes for many minutes — include moving through a tunnel toward a white light, greeting relatives no longer alive, and overhearing conversations between family members in another room. A new study from the University of Michigan Medical School shows how the brain sends signals to the heart in the moments before death. It is this flurry of mental activity that is key to cardiac demise, the researchers say, and quite probably the foundation of near-death experiences as well.
“Reduction of oxygen or both oxygen and glucose during cardiac arrest can stimulate brain activity that is characteristic of conscious processing,” Dr. Jimo Borjigin, lead author of the study, stated in a press release. These current results combined with previous research provide a scientific framework for the near-death experiences reported by many cardiac arrest survivors.
It’s a common assumption that if your heart stops, blood will stop flowing to the organs in your body and once the brain becomes starved of oxygen, death occurs. In this description, the heart is the lynchpin in the process. However, University of Michigan scientists say the brain may be performing the lead role in the process of death.
To better understand the neurobiology of death, the researchers induced asphyxiation in nine rats. Meanwhile, they monitored and examined the heart and brain simultaneously using an electrocardiomatrix, a technology developed in the Borjigin laboratory. These techniques uncovered mysteries.
Remarkably, the brain is much more active during the dying process than in the waking state, the researcers say. In the 30-second period after the animal's hearts stopped beating, the researchers observed an immediate release of more than a dozen neurochemicals while high-frequency brainwaves called gamma oscillations increased. This activity seemed to trigger a connection between the brain and the heart. Following a steep fall in the heart rate, the researchers watched (via the electrocardiomatrix) as brain signals synchronized with the heart rhythm, beat for beat.
Borjigin believes a similar, elevated level of brain activity may also happen during the human experience of "near death" and it is this that gives rise to a heightened state of consciousness, including the visions experienced by survivors of cardiac arrest.
Importantly, when Borjigin and her colleagues blocked the signals flowing from the brain to the heart, they were able to delay, significantly, ventricular fibrillation — a quivering of the lower chambers of the heart that prevents it from pumping. If with drugs you could create a “blockade of the brain’s electrical connections to the heart during cardiac arrest,” Borjigin noted, it might be possible to “improve the chances of survival in cardiac arrest patients.”
Source: Li D, Mabrouk OS, Liu T, et al. Asphyxia-activated corticocardiac signaling accelerates onset of cardiac arrest. Proc Natl Acad Sci. 2015.