My best argument is that there are some studies with induced cardic arrest in people and in animals. When you induce cardiac arrest, then within one second the blood flow to the brain is zero. Within one second people are unconscious. The body reflexes are gone, wich is a function of the cortex of the brain. The brainstemreflexes are gone. People don't breath anymore. When you measure the EEG of the brain, after an average of 15 seconds: a total flatline. So, in the studies of induced cardiac arrest in people or animals, the brain doesn't function anymore after an average of 15 seconds.
Ergo, in the studies of NDE's, most people must have a flat EEG after an average of 15 seconds and yet they have an enhanced consciousness, a coherent experience and all the logic thinking faculties seem to function well.