Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain
Gang Xu, Temenuzhka Mihaylova, Duan Li, Fangyun Tian, Peter Tran Nguyen, Rosemary Berens Netzband, Mohamad Ziyad Al-Fahhad, Tayyab Tariq, Jimo Borjigin
Proceedings of the National Academy of Sciences, Vol. 120, No. 19
Summary
EEG analysis of four comatose dying patients following withdrawal of ventilatory support found that two exhibited a marked surge in gamma oscillation power and interhemispheric connectivity at the moment of cardiac death. The surge was concentrated in the posterior cortical 'hot zone' - the region most associated with conscious processing - and in temporo-parieto-occipital junctions. The findings parallel animal studies of cardiac arrest and suggest the dying brain may generate conditions associated with heightened consciousness, offering a neural correlate candidate for near-death experiences.
Abstract
The brain is assumed to be hypoactive during cardiac arrest. However, animal models of cardiac and respiratory arrest demonstrate a surge of gamma oscillations and functional connectivity. To investigate whether these preclinical findings translate to humans, we analyzed electroencephalogram and electrocardiogram signals in four comatose dying patients before and after the withdrawal of ventilatory support. Two of the four patients exhibited a rapid and marked surge in gamma power, cross-frequency coupling of gamma waves with slower oscillations, and increased interhemispheric functional directed connectivity in gamma bands. High-frequency oscillations paralleled the activation of beta/gamma cross-frequency coupling within the somatosensory cortices. Importantly, both patients displayed surges of directed connectivity at multiple frequency bands within the posterior cortical 'hot zone,' a region postulated to be critical for conscious processing. This gamma activity was stimulated by global hypoxia and surged further as cardiac conditions deteriorated in dying patients. These data demonstrate that the surge in power and connectivity of gamma oscillations observed can select and process information in dying patients.
Citation
Gang Xu, Temenuzhka Mihaylova, Duan Li, Fangyun Tian, Peter Tran Nguyen, Rosemary Berens Netzband, Mohamad Ziyad Al-Fahhad, Tayyab Tariq, Jimo Borjigin. (2023). Proceedings of the National Academy of Sciences. Vol. 120. No. 19. DOI: 10.1073/pnas.2216268120
https://doi.org/10.1073/pnas.2216268120