So how many of your specks are required, of your whole being, to function correctly and in relative harmony with the other specks, in order to cause you to function?
The latest estimate is ~one hundred billion. The technical word for "speck" is neuronWiki
What makes those specks do the right or wrong thing?
Because they are wired properly. It is the same reason your computer works instead of bursting into flames or just sitting there doing nothing.
Do you suppose they each have a conscience, as we do?
No, that is really very, very silly. Where would the "conscience" be? What part of a neuron. What happens if one neuron doesn't like another neuron... WAIT! Why am I writing this garbage? The whole idea is as ridiculous as thinking a fingernail
could have a conscience.
Do you think it is connected with ours?
I had better be, hadn't it! What would happen if
(i) your spleen disagreed with you on a matter of the Death Penalty, or
(ii) if your kidney thought that going to Las Vegas was a good idea, whilst your left ear did not?
(iii) What happens if just a few cells of your big toe wanted to vote Republican, but the rest of the cells wanted to vote Democrat?
The sum total of neurons plus a few other bits is
our brain - part of the brain, memory, creates a conscience. We all have a different one.
Why has this anything to do with Near Death Experiences?