Here are some arguments against current scientific ideas about Near Death Experiences:
First, Lack of Oxygen to the brain:
Hogan: Lack of oxygen causes stupor without memories of the experience. People experiencing NDEs report enhanced consciousness not stupor and they remember their NDE. "Dr. Fred Schoonmaker, a cardiologist from Denver, had by 1979 carried out investigations of over 2,000 patients who had suffered cardiac arrests, many of whom reported NDEs. His findings showed that NDEs occurred when there was no deprivation of oxygen." The primary features of acceleration-induced hypoxia, however, are myoclonic convulsions (rhythmic jerking of the limbs), impaired memory for events just prior to the onset of unconsciousness, tingling in the extremities and around the mouth, confusion and disorientation upon awakening, and paralysis, symptoms that do not occur in association with NDEs. Moreover, contrary to NDEs, the visual images Whinnery reported frequently included living people, but never deceased people; and no life review or accurate out-of-body perceptions have been reported in acceleration-induced loss of consciousness.

Parnia raises another problem: When oxygen levels decrease markedly, patients whose lungs or hearts do not work properly experience an “acute confusional state,” during which they are highly confused and agitated and have little or no memory recall. In stark contrast, during NDEs people experience lucid consciousness, well-structured thought processes, and clear reasoning.

Next: Brain activity

NDEs cannot be caused by brain activity during CPR because CPR patients report confusion and amnesia while NDErs report lucid experiences. NDEs often begin before CPR is administered and the quality of consciousness and the pattern of events in NDEs does not change once CPR is started. Also, if consciousness in NDEs is caused by CPR, the patients should remember the pain of compressions and cracked ribs that sometimes occur during CPR, but NDErs do not feel the pain from CPR.

Finally, according to a Neurosurgeon named Greenfield: ""It’s very unlikely that a hypoperfused brain (someone with no blood flow to the brain), with no evidence of electrical activity could generate NDEs. Human studies as well as animal studies have typically shown very little brain perfusion (blood flow) or glucose utilization when the EEG is flat. There are deep brain areas involved in generating memories that might still operate at some very reduced level during cardiac arrest, but of course any subcortically generated activity can’t be brought to consciousness without at least one functioning cerebral hemisphere. So even if there were some way that NDEs were generated during the hypoxic state (while the brain is shut off from oxygen), you would not experience them until reperfusion (blood flow) allowed you to dream them or wake up and talk about them."

What do atheists have to say about these arguments for an afterlife?