An [“astonishing story”:http://www.newscientisttech.com/article.ns?id=dn9038&feedId=online-news_rss20] from the _New Scientist:_ an engineer at the University of Illinois has built a prototype retinal cell out of silicon. The idea is to replace damaged cells in human retinae with something that is a lot better than nothing. People have played around for years with the idea of implanted surrogate sensory organs which would transmit signals to the nerves behind.
What’s enchanting about this one is that it doesn’t supply electrical signals directly. It is of course electrical but the way it works is that light deforms a piezo-electric crystal which is turn squeezes out a drop of neurotransmitter onto the nerve cells behind, and this _chemical_ stimulation causes the other end to send an electrical impulse. So it turns out that all the science ficiton had things the wrong way round.
All this puts me in mind of Dennett’s essay, referenced by HEB some time back, about the man who is slowly turned into a cyborg: at what point does he stop being himself?