Is it possible that the human brain is activated by dying processes?

In a recent study published in PNASresearchers examined neuronal activity in dying human brains before and after clinical discontinuation of ventilators to investigate whether the dying process may involve the human brain. .

study: A surge in neurophysiological coupling and connectivity of gamma oscillations in the dying human brainImage Credit: Piyaphat_Detbun/Shutterstock.com

Background

Near-death experiences (NDEs) are biologically inconsistent with our basic understanding of the dying brain, which is supposed to fail in such situations. However, animal studies of respiratory and cardiac arrest have reported conflicting results.

The authors have previously demonstrated that abrupt termination of circulatory function and/or acute hypoxia enhances gamma (γ) activity in healthy animals, enhancing directional and functional coupling in oscillations. .

Elevated high-frequency type vibrations, which may be a measure of consciousness, have been observed in critically ill patients.

However, brain function during cardiac arrest is not fully understood. Apparent loss of consciousness is always associated with cardiac arrest, but it is unknown whether patients can retain subconscious consciousness upon death.

About research

In the current retrospective study, researchers investigated neural correlates in dying humans that may be involved in subjective perceptions reported by near-death experiences.

This study included four comatose, moribund patients admitted to the University of Michigan Neurological Intensive Care Unit (NICU) since 2014 with anoxia and extensive intracerebral hemorrhage associated with cardiovascular arrest. The region underwent electroencephalogram (EEG) evaluation.

The patient showed no overt signs of consciousness or spontaneous behavior in the last days of life, as indicated by the scores on the Glasgow Coma Scale.

To measure functional brain activity before and after cardiac arrest, we analyzed EEG signals obtained before and after discontinuation of ventilatory support. In particular for the following properties: (i) local and long-range phase-amplitude coupling (PAC) between low- and high-frequency oscillations; (ii) Temporal dynamics of EEG power. (iii) directional and functional cortical connectivity across a range of frequencies, including theta, alpha (α), and beta (β) oscillations;

In addition, electrocardiogram (ECG) signals of four patients were evaluated. Prior to EEG evaluation, moribund stages were classified based on EEG and ECG features.

Stage 1 (S1, baseline) represents the final hours of life while on mechanical ventilation. S2 represents the period from ventilator weaning to the acute suppression of the patient’s EEG findings. The S3 endo was described using his ECG characteristics of the Borjigin Institute’s electrocardiogram (ECM) method.

result

Global hypoxia resulting from withdrawal of ventilator support increased γ activity in two patients (Pt1 and Pt3) with a history of seizures, as indicated by elevated absolute EEG power in the γ frequency band. (>25Hz) significantly, rapidly and transiently.

Surges were local within the temporal-parietal-occipital (TPO) junction and global between the temporal, occipital, and zonal and contralateral prefrontal cortices. In addition, the team found a surge in inter-frequency-type coupling between gamma oscillations and slow oscillations (below 25.0 Hz) and enhanced directional and functional coupling in the gamma band between the right and left hemispheres of the brain. Observed. .

High-frequency oscillatory movements occurred in parallel with activated β/γ interregional crossovers (crPAC) in the posterior cortex with slower oscillations in the prefrontal cortex.

In particular, two patients showed surges of directional and functional connections in several frequency bands (between 25 and 150 Hz) in the posterior cortical ‘hot zone’, a key site for conscious processing. γ activity spiked further as the patient’s cardiac condition worsened.

Near death, we observed increased PAC, crPAC and γ synchrony of γ oscillations in the posteriorly located hot zone. Furthermore, long-range γ synchrony between the posterior hot zone and the frontal lobe was also increased.

Global, long-range, and interhemispheric communication in γ-oscillating movements between prefrontal and temporal-parietal-occipital regions after rapid local γ-activation in occipito-parietal-occipital regions in dying humans Observed brain.

The somatosensory cortex (SSC) responded most quickly to hypoxia, as indicated by a momentary surge of γ power in the somatosensory cortex during S2.

Interregional coupling between cortical γ-oscillating motion and β-oscillating motion in the prefrontal, dorsolateral prefrontal cortex (DLPFC), and ventrolateral prefrontal cortex (VLPFC) regions.

Decreased heart rate further enhanced β-γ PAC in the left SSC, and γ-oscillating motion in the right SSC showed increased interregional coupling with β-oscillation in prefrontal cortex regions.

Our findings link centralized homeostatic regulation of respiration to activation of the cerebral cortex near death, consistent with the possible involvement of homeostatic circuits in animal and human consciousness.

Elevated heart rate, possibly due to increased sympathetic activity during S2 after removal of the ventilator, was only observed in two individuals showing a surge in γ activity during the course of death.

Our findings indicated that enhanced cortical activation during the death process may be regulated by the autonomic nervous system (ANS). The predominantly observed activation of the right hemisphere following hypoxia during S2 indicated that the activated β/γ PAC function may be of sympathetic origin.

This finding provided a potential EEG signature for an out-of-body experience (OBE), a common component of NDE. The surge in γ power in her VLPFC region during early death was striking and likely due to electromyographic (EMG) contamination of the EEG data.

Conclusion

Research results showed that the dying human brain could be activated, as evidenced by increased neurophysiological coupling and functional and directed connectivity of γ-oscillations. rice field.

However, it was unclear whether hot zone activation was associated with subjective experience. Surges can be accidental or pathological.