I doubt this question's been asked...

In actuality, the human head does remain conscious fifteen to twenty seconds after decapitation.

LOLOWNED.

Sometimes, if shock hasn't killed you prior.

There have been tests done, and evidence to show that it DOES infact remain concious.
For example, this scientist was getting decapitated, and asked a friend to see how many times he could blink after the head was severed.
He done it for 17 secs.

  That is a complete myth!  It never happened!  Sorry you fell for it!   Knocking a person unconscious is very easy to do without cutting their head off, imagine how easy it is to do while cutting the head off!  I have heard of the myth you are quoting, it has been proven a myth many times over!!  Sorry, but it simply is not possible.