Near-Death High-Frequency Hyper-Synchronization in the Rat Hippocampus
Yujiao Zhang, Zhenyi Li, J. Zhang, Zongya Zhao, Hongxing Zhang, M. Vreugdenhil, Chengbiao Lu
Frontiers in Neuroscience July 31, 2019 DOI: 10.3389/fnins.2019.00800 via Semantic Scholar
Summary
Near-death experiences (NDE) involve enhanced perception and memory, and have been linked to a surge in high-frequency brain oscillations. In anesthetized rats dying from an overdose of chloral hydrate, a surge in beta and gamma band power occurred in the hippocampus, with gamma power specifically tied to impending death. Theta band power was suppressed. Cardiac arrest only developed after breathing stopped and all oscillatory activity collapsed, showing that the high-frequency surge is not exclusive to cardiac arrest. The gamma synchronization in the CA1 region may contribute to NDEs that occur both with and without cardiac arrest.
Study at a glance
| Characteristics | Experimental animal study Peer reviewed |
|---|---|
| Population | Anesthetized rats |
| Keywords | Medicine Biology |
| Citations | 13 |
| Key finding | The high-frequency oscillation surge before death is not limited to cardiac arrest, and the increase in gamma synchronization in CA1 may contribute to near-death experiences. |
Abstract
Near-death experiences (NDE) are episodes of enhanced perception with impending death, which have been associated with increased high-frequency (13–100 Hz) synchronization of neuronal activity, which is implicated in cognitive processes like perception, attention and memory. To test whether the NDE-associated high-frequency oscillations surge is related to cardiac arrest, recordings were made from the hippocampus of anesthetized rats dying from an overdose of the sedative chloral hydrate (CH). At a lethal dose, CH caused a surge in beta band power in CA3 and CA1 and a surge in gamma band power in CA1. CH increased the inter-regional coherence of high-frequency oscillations within and between hippocampi. Whereas the surge in beta power developed at non-lethal chloral hydrate doses, the surge in gamma power was specific for impending death. In contrast, CH strongly suppressed theta band power in both CA1 and CA3 and reduced inter-regional coherence in the theta band. The simultaneously recorded electrocardiogram showed a small decrease in heart rate but no change in waveform during the high-frequency oscillation surge, with cardiac arrest only developing after the cessation of breathing and collapse of all oscillatory activity. These results demonstrate that the high-frequency oscillation surge just before death is not limited to cardiac arrest and that especially the increase in gamma synchronization in CA1 may contribute to NDE observed both with and without cardiac arrest.