Neurobiological basis of happiness and absence of fear in the near-death experience: evidence from dying rats

Mariana Santos

Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of

Tuesday, October 13 · Poster Session 1 · Mission Bay Room

Poster

Mariana Santos, Danbi Ahn, Eun Ah Jo, Juping Xing, Guanghai Nan, Nari Kang, Yonhee Ryu, Bae Hwan Lee, Hee Young Kim

Mariana Santos — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of
Danbi Ahn — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of
Eun Ah Jo — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of
Juping Xing — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of
Guanghai Nan — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of
Nari Kang — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of
Yonhee Ryu — Korean Medicine Fundamental Research Division, Korea Institute of Oriental Medicine, Daejeon, Daejeon, Korea, Republic of
Bae Hwan Lee — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of
Hee Young Kim — Department of Physiology, College of Medicine, Yonsei University, Seoul, Seoul, Korea, Republic of

Near-death experiences (NDEs) have been reported in various critical conditions such as asphyxia, cardiac arrest, prolonged intensive care unit stays, and traumatic brain injury. NDE prototypical features include seeing a bright light while entering a tunnel, enhanced happiness, absence of fear, feeling deep peace, and vivid autobiographical memories. In this study, we particularly focused on the neurobiological processes driving enhanced happiness and absence of fear. Death was induced in Sprague-Dawley rats through asphyxiation by discontinuing the administration of 0.5% oxygen and 1.5% isoflurane used for anesthesia. Brain laser doppler and electrocardiography showed that asphyxia induced a rapid decline in cerebral oxygen levels, followed by cardiac arrest within five minutes of oxygen cessation. Electroencephalographic recordings from the parietal cortex revealed a clear transient surge of synchronous gamma- and beta-band oscillations within the first 3 minutes following asphyxia, a pattern associated with waking consciousness. Additionally, fiber photometry revealed an increase in dopamine levels in the nucleus accumbens (NAc) after asphyxia, with in vivo extracellular recordings showing a rapid decrease in single-unit firing rates of central amygdala neurons, which are implicated in fear processing. Collectively, these findings indicate that cerebral oxygen deficiency augments dopamine release in the NAc while concomitantly reducing neuronal activity in the amygdala. These neurochemical and electrophysiological alterations may contribute to the enhanced happiness and absence of fear experienced during NDEs. Further research is needed to delineate the specific neural pathways mediating these changes.