I (He-Ping Cheng) proposed "the four-stage of dying" theory：
The first stage is the orderless brainwaves period. If the dying survived from this stage, there may be life review and unpleasant near-death experience. The second stage is the weak brainwaves period. If the dying survived from this stage, there may not have any memory. This is the stage when most people survived from dying. The third stage is the surges of brainwaves period(γ neural oscillation). Brain starts its all "defense mechanism", and secretes neurotransmitters. These neurotransmitters will release countless images and sensory information, resulting in pleasant near-death experience. The fourth stage is the termination of brainwaves period. This is the determination of death. The theory will be confirmed or corrected in the future.
1. In 2009,Lakhmir S. Chawla found the surges of brainwaves(γ neural oscillation) in dying patients(60-100Hz)：
2. The γ neural oscillation was already found in Long-term meditators in 2004(80-130Hz)：
3. In 2013,Jimo Borjigin found four states of brainwaves including γ neural oscillation in dying rats. ：
4. Near-death experiences have two types：pleasant cases are more than unpleasant cases：