|Continuity of Consciousness After Brain Death||Memory|
The Wave of Death
Recent studies have provided strong evidence that consciousness arises from the synchronized neuronal firing in the resting state networks, which oscillate at very low frequency (0.02 - 0.1 Hz) in EEG.
Rat brains also have the resting state networks (Lu et al., 2012). Remarkably, the very slow oscillation unique to the networks emerged after rats were decapitated (beheaded) (van Rijn et al., 2011). Following decapitation, a fast and global loss of power of the EEG was observed; the power in the 13-100 Hz frequency band decreased exponentially to half the initial value within 4 seconds. Then, an oscillation characteristic for the resting state activity appeared. This oscillation is called the Wave of Death, which was present not only for rats decapitated while awake, but also for those decapitated under anesthesia. Since rats were not conscious under anesthesia and the resting state activity can produce consciousness, the result shows that rats could regain consciousness after being killed!
The Wave of Death may correspond to the end-of-life EEG surge observed in humans (see Chapter 13). Instead of converting EEG into the bispectral index (BIS), it should be interesting to see if humans also exhibit the Wave of Death in EEG.
Continuity of Consciousness
The surge in the end-of-life EEG lasts only 30 -180 seconds for humans. However, the conscious near-death experiences may persist for several hours while the EEG remains flat. Even blind persons can have the out-of-body experience. This phenomenon can be explained by the Geon Hypothesis which holds that consciousness arises from the formation of a geon. Once a geon is formed, it can exist on its own for a finite period of time.
Can Everyone Have Consciousness After Brain Death?
About 20% of people who survived cardiac arrest had NDEs (van Lommel et al., 2001; 2006 PDF file). Not only can these people have conscious perception in the near-death events, they can also remember the incidences. The hippocampus is essential for memory, but not required for conscious perception. Therefore, only those who had a functioning hippocampus could remember NDE.
In the 2009 paper, Chawla and colleagues reported that seven out of seven patients studied (100%) exhibited the end-of-life EEG surge. In 2011, more than 100 patients have been studied. About 80% of them showed the EEG surge [presented in the conference, Toward a science of consciousness: Brain, mind, reality (Stockholm, Sweden, May 3–7, 2011)]. The Wave of Death was observed in all 17 rats decapitated.
Author: Frank Lee