REVIEW OF “EEG SIGNATURE OF NEAR-DEATH-LIKE EXPERIENCES DURING SYNCOPE-INDUCED PERIODS OF UNRESPONSIVENESS” BY MARTIAL ET AL”.
As previously mentioned, em 2009, A equipe de Lakhmir Chawla detectou sobretensões elétricas em fim de vida (ELES) in seven patients, occurring between 3 to 5 minutes after cardiopulmonary arrest. Oito anos depois, eles conseguiram replicar parte desses resultados: 13 fora de 18 patients exhibited ELES. No 2009 artigo, these ELES were proposed as a potential neurophysiological cause for Near-Death Experiences (EQMs).
Chawla destaca que os estudos de Auyong (2010), Vá em frente (2013), e van Rijn (2011) support his findings. No entanto, no primeiro estudo, o momento exato da parada cardíaca não está incluído, no segundo, the EEG activity occurs in mice within 30 seconds of cardiopulmonary arrest as expected, e Dr.. Borjigin herself criticized that Chawla’s results differed from those collected by her team. In the third study, it is ruled out that the experiences found in decapitated rodents could be associated with any type of consciousness, dado que o fenômeno ocorre em camundongos anestesiados e não anestesiados.
Os resultados do Norton (2017), Dormindo (2021), Reagan (2018), DeVries (1998), com um total de 197 casos, e a meta-análise de Pana (2016), involving seven human studies and ten animal studies, did not validate Chawla’s findings and found generalized brain activity decline or none at all after cardiopulmonary arrest.
When we consider that some NDEs occur within three minutes of cardiac arrest due to their in-hospital genesis and proper resuscitation protocols, it is difficult for ELES to be the cause of NDEs. Na verdade, ELES seem to result from the depolarization of neurons in a severely impaired brain.
The latest of these studies is by Martial et al. (Julho 2024), which shows that during induced syncope (fainting), individuals who experience something akin to an NDE present EEGs (electroencephalograms) consistent with a lack of consciousness: an increase in theta and delta waves. The study notes the presence of beta waves but not an increase compared to pre-syncope levels. Interestingly, the study interprets these patterns as indicators of conscious brain activity, referring to studies that show this pattern only in patients who are ill or under the effects of psychedelics, where brain activity decreases.
From what we know from EEGs, theta and delta waves appear when a subject is not experiencing consciousness, and they are used as measures of unconsciousness during surgeries under anesthesia. Therefore, Martial’s study supports the viewpoint of the absence of brain activity during simple syncope, corroborating that the brain is highly sensitive to vascular issues such as a lack of arteriovenous pressure.
Meanwhile, Nigel Shaw, da Universidade de Auckland, Nova Zelândia, has developed a series of arguments highlighting the inadequacy of the naturalistic approach—i.e., that brain activity is what produces NDEs—to explain such experiences.
First, Shaw explica como os movimentos musculares podem ser confundidos com ondas cerebrais, creating a false impression of brain activity. No entanto, this seems unlikely since EEGs have been recorded in some cases in patients with no movement.
Second, Shaw refers to the poor timing of death determination in some of the studies that found gamma activity in perimortem EEGs. Em alguns estudos, EEGs are clearly recorded before cardiac arrest, in others when no pulse is detected, and in others during an effective cardiopulmonary arrest.
Shaw’s strongest argument comes from dog studies that found gamma activity in EEGs originates from the amygdala, not the cortex, meaning that this activity cannot be proposed as the cause of NDEs.
Adicionalmente, Shaw argues that the relationship between gamma waves and consciousness has never been fully established. For example, someone can produce gamma waves in an EEG while being under anesthesia.
Finalmente, Shaw emphasizes that in states induced by psychedelics, where some NDE characteristics are reproduced, todo o espectro de ondas cerebrais registradas por EEG, incluindo ondas gama, decreases, adding more difficulty to the possibility that such perimortem waves could be responsible for NDEs.
For more information, we share the link:
Reseña elaborada por Òscar Llorens i Garcia
BIBLIOGRAPHY
Caracterização de surtos eletroencefalográficos em fim de vida em pacientes críticos. https://pubmed.ncbi.nlm.nih.gov/28145850/
O modelo de atividade de banda gama da experiência de quase morte: uma crítica e uma reinterpretação. https://f1000research.com/articles/13-674