There have been several programs in recent months that have tried to explain the scientific and medical reasons for these experiences. Of course, these scientists feel that it is the mind that is using its last defense. There are certain common threads: a person floating overhead observing the event, a long dark tunnel and a bright white light at the end of it.
I think that people are desparate to have an answer as to what lies ahead after death. Most people that have had them usually accept the thought of death and are reassured that life continues on in another form.