Can a head still be alive after decapitation?
Even worse to imagine: Could the decapitated head still be conscious for a bit? Perhaps yes.
After the heart stops beating, we consider that someone has died. But, after the heartbeat stops, we also know that sometimes, the heartbeat can come back by itself. This is called
autoresuscitation. In this case, someone that appeared dead for a few minutes may not have actually died.
But the situation is different for the brain than for the heart. When there is a lack of blood flow in the absence of a heart that pumps it, or when there is intrinsic brain injury and blood cannot get in, the situation is tricky. Brains are very sensitive to being deprived of oxygen and energy supply, and
various degrees of brain injury occur. Depending on how long the energy fuel to the brain is absent, brain function can remain alive to various degrees and be rekindled to a degree we neuroscientists do not yet fully know. We know that brain function is seriously disturbed, with variable permanence of function loss depending on how long the brain has not had energy.
The end result of how functional such a damaged brain will come out is one of the biggest challenges we have to learn more about.
After an injury, a whole sequence of consecutive processes occurs that is called
secondary brain injury and is triggered by the insult to the brain in the first place. And these processes often cause tremendous damage, and sometimes more than the actual first injury.
For example, a hard blow to the head can result in a bruise or bleeding in the brain, which can be removed by surgery in certain cases. Despite the bleeding being stopped or removed, however, the surrounding brain will sometimes start swelling and bruising even more over the subsequent days, like a big bruise on the thigh goes through stages and color changes. There is not yet a preventive therapy for this, but we know that some factors can make this process worse, such as blood pressure that is too low or lack of oxygen to the brain during the healing phase.
Imagine a broken bone: The cast is just the first step, and there is swelling, pain and weakness for weeks to come. In the brain, the process is more granular. And in neuroscience, we are just now beginning to understand this cascade of events.