A recent paper described the accidental recording of EEG brainwave information right at the time of death, from a patient who had the unfortunate outcome of dying during a brain scan procedure. The patient was an 87-year-old man who had been hospitalized after a fall in which he hit his head; surgeons relieved pressure on his brain with surgery, but 2 days into hospitalization the patient showed a rapid decline in neurological status that led to the EEG. Some seizure activity in the brain was identified. Then, while he was still in the scanner, the patient experienced a cardiac arrest and died (he had a "do not resuscitate" order on file). The study's authors held off on publishing for 6 years because they weren't sure how much could be generalized from a single case study, but eventually they decided to share these accidental results with the scientific community.
The most interesting thing about this case report was an increase in the relative percentage of gamma-band EEG readings in the seconds immediately before and after cardiac death. Gamma waves are the highest-frequency type of brain activity and are often associated with active problem-solving or a high level of mental focus. Some of that percentage increase occurred because of a relative decrease in other types of brain waves, alpha and beta, that are associated with wakeful alertness. Furthermore, there was increased synchronization or coherence between different regions of the brain, particularly in the gamma-wave frequencies. Coherence between brain regions is often seen in alert, introspective states such as meditation. The study's authors note that reduced alpha waves may be associated with less intentional (Narrative-level) thought and greater openness to potentially irrelevant stimuli; at the same time, increased gamma activity might suggest increases in Intuitive-level progresses that are more intensely experienced but less goal-directed. Overall, the researchers note that this modulation of brainwaves from the alpha to the gamma frequency is typical of brain states when people are engrossed in memories and in conscious processing of their experiences.
Like many studies that are hyped as "explaining near-death experiences," this study raises more questions than it answers. First, it's important to note that these brainwave readings weren't necessarily associated with any of the classic near-death experience phenomena like a tunnel of light or a life review. We actually don't know whether they were or not, because the patient wasn't able to describe his experience afterwards. It's also possible that actual death might not be associated with the same phenomena as near-death, although the circumstances involving cardiac arrest in this case are very similar to those in which near-death phenomena are most often reported. Additionally, I would note that some of the best-documented near-death cases occurred in people who by most reasonable measures were actually having "death experiences" due to the prolonged cessation of both brain activity and spontaneous heartbeats -- in past centuries, no one could have survived them.
Because the patient in the recently published case had experienced a brain injury with swelling, followed by seizure activity, it's impossible to rule out the possibility that rhythmic EEG patterns were the effect of head trauma. He had also been given "significant doses of antiseizure medication" while he was in the hospital. Nevertheless, the study showed a clear difference between the patient's brain activity at the time of death and his brain activity while he was having a seizure, which had also happened once during the EEG monitoring period. This figure from the original article shows the difference: In the middle panels ("B" section), notice the much more yellow color (indicating predominant gamma-wave activity) between the two red lines on the far right side of the square, which is when the patient died; that gamma shift is not seen between the two red lines on the left side of the square, when the patient was having a seizure. The shift into the gamma spectrum of EEG activity, therefore, might be particularly linked to the patient going into cardiac arrest.
The authors note that although their findings are unique in human research, they are almost identical to what was seen in an experimental study of dying rats. In that study from 2013, researchers found that cardiac arrest (caused by lethal injection) "induces an organized sequence of neurophysiologic events that was consistent across all rats studied." It was also very consistent with the single human case. Right at the time of death, the rats showed a strong decrease in all EEG frequencies except for gamma waves, and gamma EEG readings that increased dramatically in the seconds immediately before and after their hearts stopped. In the rat study, researchers noted that the level of coherence and connectivity seen in a dying brain "far exceeds that observed during the waking state."
The current whole-brain EEG results are unique in the literature, but there are other EEG data obtained from humans at the time of death. In a different brain-monitoring study of humans, there was no evidence of an electrical surge in any brainwave frequency, which might be seen as a contradictory result. But the authors of the new study note that the routine brain-monitoring results presented in the other paper were obtained from readings of the frontal lobe only, and that their data are the first presentation of EEG readings from multiple areas of the brain at the time of death. A lack of increased activity in the frontal lobe is perfectly consistent with a hypothesis of decreased Narrative processing, while increased Intuitive-level activity could manifest mainly in other regions of the brain. This is in fact the central hypothesis of a current study that I'm working on, using EEGs to monitor the brains of people participating in psychotherapy. Our hypothesis is that moments of insight will be associated with spikes in higher-frequency EEG activity (delta, theta, or gamma waves) in parts of the brain other than the frontal lobes.
Perhaps the most striking finding from this study is that a dying brain showed signs not just of increased activity, which could be a kind of final electrical discharge, but also signs of increased pattern or coherent behavior. This exactly the opposite of what one might expect if mental functioning was breaking down at the moment of death. Bernardo Kastrup notes that ...
... there might indeed always be a neuron firing somewhere [in near-death experiences]. But this isn't a relevant point, is it? The point is whether the kind of brain function that ordinarily correlates with complex dreams can be plausibly expected to have been present ... . If chaotic, impaired, residual cortical function could explain the confabulation of a complex and coherent 'trip to heaven,' then such residual cortical function should suffice for our nightly dreams too, shouldn't it? But we know it doesn't. The [materialist] argument is analogous to claiming that a car should drive better and faster when everything in it is broken, except for the spark plugs.
The facts are that, in some cases, people report rich sensory near-death experiences in the absence of brain function; that highly coherent brain states are associated with memory and dreaming; and that in the latest EEG study, a patient showed strong and coherent brain activity just before his body shut down altogether. We can't know what his experience was in those final moments, but many people have reported a burst of "terminal lucidity" when sitting with a dying loved one. Somehow the brain appears to become more coherent just before it stops working, which not what our common brain-as-machine metaphors would suggest. Perhaps it is only the Narrative mind that shuts down in these cases, leaving behind or even restoring an ability to function at the Intuitive level of thinking. In the new EEG study, the shutdown of the Narrative mind could be seen in the drop in alpha waves; in the former frontal-lobe EEG studies, it could be seen in the decrease of electrical activity across the board in that one highly Narrative region of the brain.
There's also some consistency between the new brainwave findings and the idea that mindfulness or attention taps into the Intuitive mind, producing a conscious experience that is often experienced as meaningful or true even though it largely bypasses the rational, language-using Narrative mind. One could even go so far as to speculate about the similarity of dying brainwaves to the brain states involved in dreaming (one tradition of yoga views all of waking life as a dream from which we wake at the point of death), to those involved in religious experiences, or to those that occur in the presence of psychedelic drugs. All of these are altered states of consciousness in which alpha and beta waves tend to be suppressed, while theta or gamma waves increase. (For instance, a slightly older study showed that a dramatic increase in gamma-wave coherence together with decreased overall EEG activity was also characteristic of the brain's behavior under the influence of ayahuasca, a South American psychedelic used for religious purposes). None of this is to say that death is exactly like dreaming, drugs, or a religious epiphany. But the current study does seem to indicate that death involves an altered state of consciousness that might involve insight and awareness -- an awakening rather than a case of the mind's programming breaking down.
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