Let's assume tissue rejection is not an issue. What would happen if you were able to connect neurons from another person's brain to neurons in your own so that they could send and receive signals? What if it was one neuron? 100? 10,000? 1 million? What would that feel like? At what point would you cease being two conscious beings and become one (or would you become three - you, other and the collective)? I think the results would be highly dependent on which neurons and how many were connected. But what if you connected 10 million neurons from one visual area to neurons in the other visual area? Would you get each person being able to see what the other sees? What other odd effects might occur?