Echoes of a dying brain

Peering into the abyss through the lens of neuroscience

“Three days he had been dead. Thrice had the sun risen and set—and he had lain dead. The children had played, the water had murmured as it streamed over the rocks, the hot dust had clouded the highway—and he had been dead. And now he was among men again—touched them—looked at them—looked at them! And through the black rings of his pupils, as through dark glasses, the unfathomable There gazed upon humanity.”

~ Leonid Andreyev (Lazarus)

In the Gospel of John, there is a relatively short passage that deals with how Jesus resurrected a man from Bethany. Lazarus—for this was his name—had already been dead for days before Jesus commanded him to come forth, effectively reviving him on the spot. Other than attending a supper six days before the passover, not much else is mentioned about Lazarus in the Gospels. In 1906, the Russian playwright Leonid Andreyev wrote a macabre account that explored the morbid implications of Lazarus’ story—a man does not simply return from the afterlife without bringing a part of it back with him. Initially, the whole town celebrated the renewal of Lazarus’ life, with family and friends overjoyed at the miracle of his being risen from the dead. But before too long, those close to him began to witness unworldly occurrences wherever he went. Word of the man who had been resurrected after being dead for several days eventually spread through all of Judea, ultimately reaching the Roman emperor himself, Augustus, who summoned Lazarus so that he may stare into the eternal void of his eyes. Gazing at the strange man’s dark pupils, the emperor was first met with the softness and warmth of the gentle embrace of the Infinite, but “when you look long into an abyss,” as Nietzsche wrote in Beyond Good and Evil, “the abyss also looks into you.” So what exactly does happen when we look into this proverbial abyss using the tools of neuroscience—and more to the point, what insights about the brain can we derive from this exercise? In this issue of ZAGROSCIENCE, I will try and shed some light on this subject by unpacking some of the most relevant neuroscientific findings from animal and human experiments.

Borjigin et al. (2013) investigated the neurophysiological state of the brain immediately following cardiac arrest. Conducted in nine Wistar rats, the study tested the hypothesis that neural signatures of consciousness could be detected in the mammalian brain after the cessation of cerebral blood flow, thereby providing a scientific framework for understanding near-death experiences (NDEs). EEG (electroencephalogram) recordings monitored electric signals in the frontal, parietal, and occipital cortices of the rats at baseline, during ketamine/xylazine-induced general anesthesia, and following cardiac arrest elicited by potassium chloride injection. The researchers then analyzed the data for variations in power density, global coherence, directed connectivity, and cross-frequency coupling of brainwaves. Results showed that within the first 30 seconds of cardiac arrest, a transient surge of synchronized high-frequency gamma oscillations (>25 Hz) enveloped the entire brain right before it flatlined. These gamma fluctuations displayed anterior-posterior-directed connectivity, meaning that the brain appeared to be preferentially transferring information from the front to the back. Additionally, these gamma oscillations demonstrated tight phase-coupling to both theta and alpha waves. Taken together, these findings suggested that the mammalian brain possesses the potential for heightened information processing, possibly sustaining subjective events such as NDEs.

Xu et al. (2023) - increase in gamma (>25Hz) power in the brain post-hypoxia

More recently, Xu et al. (2023) investigated whether the sudden increase in power and functional connectivity for the gamma frequency band observed in animal models of cardiac and respiratory arrest translates to humans. To do so, the authors retrospectively examined EEG data in four comatose patients who died while being monitored in the neurointensive care unit, analyzing changes in scalp recordings before and after ventilatory support was withdrawn. The primary objective here was to identify telltale neural signs of the dying process. Far from going quiet as a consequence of global hypoxia, results demonstrated that the dying human brain may actually become activated as evidenced by the presence of increased gamma activities throughout the cortex, validating previous findings in animals. Specifically, the researchers observed a surge in absolute power, local and long-range phase-amplitude coupling, as well as functional and directed connectivity in the gamma range. Findings were especially manifest in regions of the brain considered critical for conscious processing, namely, the so-called “hot zone” of the temporo-parieto-occiptal (TPO) junction. Two important caveats must be acknowledged here: first, the very small number of subjects studied—which is unsurprising given the ethical nature of the experiment—and the fact that heightened gamma wave dynamics were found in only two of them, both of whom presented with a history of seizures. The paper noted the following:

Patients with epilepsy exhibit symptoms of spontaneous visual hallucinations and out-of-body experience (OBE) (43–46); stimulation of the right TP junction (TPj) in epilepsy patients reliably induced OBE (47, 48). Furthermore, OBE from seizure patients show similar features with that of NDE (49, 50). In this study, both patients with a seizure history showed persistently high levels of intrahemispheric gamma functional (Fig. 4B and SI Appendix, Fig. S4B) and directed (Fig. 5B and SI Appendix, Fig. S5B) connectivity at both left and right TPj. Our data provide a potential EEG signature of OBE, a commonly reported component of NDE (3, 51).

At this stage, a lot more research is required to ascertain whether findings pertaining to oscillatory neural dynamics in this context is how the brain actually behaves, a mere statistical fluke, or the symptom of a hypoxic epileptic cortex.

---

If you are interested in learning more about epilepsy, see my article:

---

In addition to being an excellent subject matter for armchair philosophy, NDEs are the closest real-life phenomena to an actual Lazarus event that can be studied empirically. Mashour et al. (2024), a recent narrative review of the scientific literature, offers interesting insights into potential neurobiological mechanisms of end-of-life conscious experiences. At the outset, the authors stated that a complete understanding of consciousness must necessarily account for these unique subjective episodes within the framework of neuroscience. One proposed neurochemical process entails the rapid release of a wide range of neurotransmitters and neuromodulators in frontal and occipital regions, including glutamate, GABA (γ-aminobutyric acid), adenosine, dopamine, norepinephrine, and serotonin. The surge in serotonin is particularly interesting. With a reported 20-fold increase 2 minutes following asphyxia and a whopping 250-fold rise after 20 minutes, the activation of serotonergic receptors in the brain is believed to give rise to powerful hallucinations. Dimethyltryptamine (DMT), the fastest acting serotonergic psychedelic that is also secreted in the brain, has been shown to spike in the visual cortex of rats following cardiac arrest. What is noteworthy is that subjective reports of DMT-induced psychedelic experiences oftentimes describe them as feeling more real than reality, which is qualitatively consistent with accounts of NDE.

---

If you are interested in learning more about psychedelics, see my article:

---

Another suggested network-level mechanism with the very sexy name of “explosive synchronization” postulates that the dying brain may find itself in a tug of war between chaos and order. As brain networks begin to break down due to hypoxia, homeostatic fail-safes may be triggered to prevent the disintegration of the functional architecture of the cortex. In this critical moment, an abrupt shift in the dynamic organization of the brain may occur, bursting it into a state of global connectivity right before flatlining, which is supported by the previously discussed EEG results pertaining to high-frequency gamma oscillations. Mashour et al. (2024) proposed a final theoretical model that may help explain EEG findings and their association with NDEs. Known as percolation, this mechanism is predicated on random probabilistic events, where cortical networks are stochastically disrupted one at a time due to oxygen deficiency. Percolating, as it were, the brain eventually reaches an inflection point marked by a bare-bones functional scaffolding consisting of a few interlinked hubs of local connections. An extensive information discharge may then arbitrarily ignite within surviving cortical nodes, momentarily coupling the integral parts of this stripped down network. The aforementioned TPO junction, which is believed to play a crucial role in sustaining consciousness, is a prime candidate for the integration of information during this highly volatile period. Ultimately, when the last remaining inter-hub connection goes offline, the entire network collapses, effectively shutting down the brain.

In this discussion of the neural biomarkers of the brain in the process of dying, it is important to provide some broader context to have a better grasp of the subject matter, beginning with the fact that NDEs are not the norm, but a deviation thereof. A systematic assessment of in-hospital cases of cardiac arrest shows that only 10%-20% of patients in recovery actually report having experienced such phenomena. Evidently, in individuals who do not live to tell their stories, it is inconceivable to cross-reference physical findings pertaining to the brain with personal testimonies. Absent subjective accounts, integrating mind and brain into a cohesive framework, which is the ultimate goal in cognitive neuroscience, becomes simply impossible. Another important consideration relates to the use of EEG. While offering great temporal resolution, it affords nowhere near the same degree of spatial accuracy as other neuroimaging modalities, such as MRI, which, alas, is much more costly and a lot less compliant with the setting of the neurointensive care unit, where end-of-life neurological patients are typically monitored. Regarding animal models of the dying brain, they do provide highly controlled experimental conditions conducive to targeted investigations of cortical dynamics, but they nonetheless—and for obvious reasons—exclude verbal responses that sample stream of consciousness—to the extent that animals even possess a level of subjectivity that can inform that of humans. A final point of interest appertains to the induction of NDE-like phenomenology in healthy controls, specifically via the measured use of psychedelics, namely DMT. Indeed, this potent serotonergic hallucinogen has been shown to instantiate phenomenological features shared with the NDE, such as transcendence of one’s own physical body, entry into alternate realms of reality, and communion with sentient entities, as per Timmermann et al. (2018). Even so, additional validation is needed to establish a bona fide DMT-model of end-of-life consciousness, given that DMT experiences may encompass an even wider umbrella of subjective attributes than NDEs, as proposed in Michael et al. (2025).

In a unique semi-autobiographical case report, Woollacott & Peyton (2021) chronicled the NDE of the second author, Bettina Peyton. In 1988, when she was 32, Peyton developed a high-risk complication during her second pregnancy in which the placenta was revealed to be obstructing the birth canal, requiring surgical intervention. She recounted her experience while under general anaesthesia—the following is an excerpt:

“Her blood pressure is too low!” My anesthesiologist’s alarmed voice has snapped me awake as if from a deep sleep. Suddenly, right in the middle of the operation, I am wide-awake. As if with a flick of a switch, I have awakened to a heightened awareness, the likes of which I have never before experienced, as if the majority of my brain, dormant all my life, has suddenly switched on. How wondrous that this super-alert state is beyond the reach of the drugs bathing my brain! I am truly awake for the first time—while under general anesthesia! It is starkly evident that this awakened self is the real me!

Just as amazing is how calm I am - given the circumstances. There is absolutely no fear. I can feel the painless tugging sensations in my abdomen of the surgery in progress. I can hear the anesthesiologist anxiously asking the surgeon about blood loss. The surgeon’s tense answer is shocking: “The baby is gone,” he says.

From over my right shoulder there bursts forth a loud expletive. “Shit! Now she has no blood pressure at all!”

In the next instant, I feel a profound stillness in the center of my chest. Something’s missing. It’s the beat of my heart. My heart has stopped. At the same time, I can suddenly see into the room. How amazing! The eyelids on my physical eyes have been taped shut to protect the corneas, yet by some other mechanism I can see perfectly clearly. There are the bags of blood hanging on the IV pole, already being transfused. My anesthesiologist is crouched on his stool next to me, oblivious to the fact that I have no heartbeat.

Thankfully for Peyton, both she and her baby girl survived the affair. Curiously, the report also claimed that parts of her recalled narrative of the incident were actually confirmed by hospital staff. Still, as far as I can tell, this validation came mostly from Peyton’s own responses to an interview that took place approximately 26 years after the fact, which, in my opinion, lacks objectivity. What is clear, however, is that her NDE had consequential effects on her identity and priorities. For example, she went from being a “strident materialist” to someone who perceived consciousness as being “fundamental and independent of brain activity […]”

As we have seen, there are considerable hurdles to overcome for gaining a deeper understanding of brain function moments before death and its phenomenological corollaries. But prior to invoking the supernatural, as was the case in Peyton’s story, Occam's razor demands that we first exhaust all possible natural explanations. One question still remains though: whatever did happen to Augustus, the Roman emperor who peered into the eyes of Lazarus? What initially struck him as the welcoming embrace of eternal space rapidly devolved into an uncanny Lovecraftian hellscape. Augustus had caught a glimpse of the Infinite, which had driven lesser men before him into madness and self-annihilation—and while he came back from the brink of it all, he was never the same again. As for Lazarus, whom Christ resurrected, he lived the rest of his life in solitude after his eyes were burned out with hot irons by emperor’s decree.

---

---

References

Borjigin, J., Lee, U., Liu, T., Pal, D., Huff, S., Klarr, D., ... & Mashour, G. A. (2013). Surge of neurophysiological coherence and connectivity in the dying brain. Proceedings of the National Academy of Sciences, 110(35), 14432-14437.

Mashour, G. A., Lee, U., Pal, D., & Li, D. (2024). Consciousness and the dying brain. Anesthesiology, 140(6), 1221.

Michael, P., Luke, D., & Robinson, O. (2025). An encounter with death: a comparative thematic and content analysis of naturalistic DMT experiences and the near-death experience. Frontiers in Psychology, 16, 1532937.

Negri, P. (Ed.). (2003). Great Russian Short Stories. Dover Publications, Inc.

Nietzsche, F. W., & Kaufmann, W. (1989). Beyond good and evil: prelude to a philosophy of the future. Vintage Books.

Timmermann, C., Roseman, L., Williams, L., Erritzoe, D., Martial, C., Cassol, H., ... & Carhart-Harris, R. (2018). DMT models the near-death experience. Frontiers in psychology, 9, 395026.

Woollacott, M., & Peyton, B. (2021). Verified account of near-death experience in a physician who survived cardiac arrest. Explore, 17(3), 213-219.

Xu, G., Mihaylova, T., Li, D., Tian, F., Farrehi, P. M., Parent, J. M., ... & Borjigin, J. (2023). Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain. Proceedings of the National Academy of Sciences, 120(19), e2216268120.