How long can brain function when heart has stopped beating?

The article below says:
"...We know the brain can’t function when the heart has stopped beating. ... the brain typically shuts down within 20-30 seconds after the heart has stopped..."

http://ift.tt/1UR1ia8

In the fifth paragraph:

Quote:

...The results revealed that 40% of those who survived a cardiac arrest were aware during the time that they were clinically dead and before their hearts were restarted. Dr. Parnia, in the interview stated: “The evidence thus far suggests that in the first few minutes after death, consciousness is not annihilated. Whether it fades away afterwards, we do not know, but right after death, consciousness is not lost. We know the brain can’t function when the heart has stopped beating. But in this case conscious awareness appears to have continued for up to three minutes into the period when the heart wasn’t beating, even though the brain typically shuts down within 20-30 seconds after the heart has stopped. This is significant, since it has often been assumed that experiences in relation to death are likely hallucinations or illusions, occurring either before the heart stops or after the heart has been successfully restarted. but not an experience corresponding with ‘real’ events when the heart isn’t beating. Furthermore, the detailed recollections of visual awareness in this case were consistent with verified events”.

For how long can the brain function after the heart has stopped beating?
Maybe a better question:
What would constitute proof that some kind of consciousness really does continue after death?

via International Skeptics Forum http://ift.tt/1UR1gix