No one can say what a 'thought' is, really. But we are figuring out what thoughts do, chemically and electrically. With that knowledge it is possible to develop thought-interactive computer chips. In fact, they've already been used with success. For bionics, this is the ultimate step in this technology. Beyond that lies the realm of the spiritual- something of which science really has nothing to say, pretend as it might. They haven't begun to spread yet, but bionics will. Science fiction is becoming fact.