Death is one of the most profound and inevitable events we experience as human beings. Despite its universality, much about death remains shrouded in mystery.
However, recent scientific advances are giving us a clearer picture of what happens to our bodies and brains when we die, including the release of specific chemicals that shape our final moments.
The Process of Dying: The Physical Breakdown
Death occurs when the body can no longer sustain its vital functions. This process often begins with organ failure, a gradual shutdown that may be prolonged in some cases, such as through terminal illness. The heart stops beating, which halts blood flow to the brain, lungs, and other organs.1
Without oxygen, the brain begins to die, and after a few minutes, brain cells become damaged beyond repair. Once the brain is deprived of oxygen, other organs and systems quickly follow.
Once the body is clinically dead and resuscitation is no longer possible, the next phase is biological death. This marks the beginning of decomposition, a natural process that breaks down the body’s tissues.2
In the first stage of decomposition, known as autolysis, cells begin to break down due to the accumulation of carbon dioxide, which leads to an acidic environment within the cells. Enzymes that were once responsible for maintaining cell function now begin to digest the cells from the inside out. This process usually begins within minutes to hours after death.
Following autolysis, putrefaction sets in. This is when bacteria that were previously kept in check by the immune system start to break down tissues, producing gases that cause the body to bloat and emit strong odors. The body turns greenish as the bacteria break down hemoglobin in the blood, releasing sulfur compounds.
Rigor mortis, or the stiffening of muscles, typically begins within two to six hours after death and peaks around 12 hours. This occurs because the body’s energy stores, which are required to keep muscles relaxed, are depleted.
After about 48 hours, the body’s muscles begin to relax again as the tissues break down further.
In the days and weeks following death, the body continues to decompose, eventually leading to skeletonization. This process is influenced by various factors, including temperature, humidity, and the presence of insects or scavengers.
While clinical death, defined as the cessation of heartbeat and respiration, is instantaneous, the end of the brain and body’s functioning is not.
Brain Activity After Death
Some processes continue for minutes or even hours after clinical death. In fact, during the early stages following clinical death, the body enters a series of steps that scientists call “active dying,” where certain chemicals are released and neuron activity spikes as the brain and body gradually shut down.
A groundbreaking 2013 study conducted on rats revealed that within 30 seconds after cardiac arrest, there was a significant increase in neural activity across various brain regions.3
This hyperactivity was characterized by synchronized brain oscillations similar to those observed during heightened states of consciousness.
Further research in human subjects supports the idea of heightened brain activity after death. In a 2022 study, researchers observed similar spikes in brain activity in a human patient after his heart had stopped, suggesting that the brain might still be processing information after clinical death.4
The Death Cocktail
In addition to heightened brain activity, a key feature of the dying process is the release of various neurochemicals and hormones that shape our final experiences.
Endorphins, the body’s natural opioids, are released in large quantities during extreme stress or trauma, including during death.5
They act to diminish pain and induce feelings of euphoria and calm, potentially easing the physical and emotional distress associated with dying.
The surge of endorphins may contribute to the peaceful and pain-free experiences often reported by people who have died and been revived, even if they had incurred serious physical injuries before dying.6
Serotonin, a neurotransmitter associated with mood regulation and perception, is also believed to be released in increased amounts during the dying process.7
Elevated serotonin levels can lead to altered states of consciousness, including visual and auditory hallucinations. This is the mechanism underlying hallucinogens like psilocybin or “magic mushrooms.”8
The surge of serotonin may explain the vivid imagery and profound spiritual experiences reported by some individuals during near-death situations.9
Massive releases of DMT are also thought to occur during death. DMT is a powerful psychedelic compound naturally produced in small amounts in the human brain, particularly in the pineal gland.10
The effects of DMT include profound alterations in perception, feelings of transcendence, and encounters with mystical entities, closely mirroring descriptions of NDEs.
Finally, because the body undergoes extreme stress during dying, there is a significant release of adrenaline and noradrenaline.11
These hormones are responsible for the fight-or-flight response, increasing heart rate and blood pressure in an attempt to preserve life.
The surge may lead to heightened awareness and rapid processing of information, potentially contributing to the phenomenon of life review reported by some individuals, where they experience a rapid playback of life events.12
The Mind After Death: Near-Death Experiences and Consciousness
One of the most intriguing aspects of death is the near-death experience (NDE). NDEs are reported by individuals who have been declared clinically dead or close to death and subsequently revived. Commonly reported elements of NDEs include feelings of peace, out-of-body experiences, seeing a bright light, or encountering deceased loved ones.
One notable study conducted by Dr. Sam Parnia and his team investigated NDEs in cardiac arrest patients.13 Published in the journal Resuscitation in 2014, the study found that 40% of patients who were revived after cardiac arrest reported some form of awareness during the period when they were clinically dead. Some even recalled specific details about their surroundings, which raises intriguing questions about the nature of consciousness.
While NDEs were once considered purely anecdotal or spiritual, there is growing scientific interest in understanding the neurological and biochemical underpinnings of these experiences.
Some researchers suggest that NDEs are linked to the brain’s final attempts to make sense of what is happening as it shuts down, aided by the release of neurochemicals such as serotonin and DMT.14
A leading hypothesis is that NDEs are caused by a lack of oxygen (hypoxia) or blood flow (ischemia) to the brain, which can trigger hallucinations and out-of-body experiences. The spike in brain activity, seen in the aforementioned studies, may also play a role in these vivid experiences.15
While there is no definitive scientific evidence to support the existence of an afterlife, NDEs suggest that the brain may retain some level of consciousness even after the heart has stopped.
However, these experiences are highly subjective and can vary widely from person to person, making it difficult to draw firm conclusions.
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