The New Scientist (www.newscientist.com) announced in 2003 that:
The world's first brain prosthesis - an artificial hippocampus - is about to be tested in California. Unlike devices like cochlear implants, which merely stimulate brain activity, this silicon chip implant will perform the same processes as the damaged part of the brain it is replacing.
The same magazine reported in October of this year (2005):
Researchers have developed several ways to convert simple, single-celled creatures into components that may prove useful in electronic circuits
So, we will shortly be able to implant a self-replicating and developing chip which replaces the functions of the hippocampus.
The job of the hippocampus appears to be to "encode" experiences so they can be stored as long-term memories elsewhere in the brain. If you lose your hippocampus you only lose the ability to store new memories.. That offers a relatively simple and safe way to test the device: if someone with the prosthesis regains the ability to store new memories, then it's safe to assume it works.
What has not yet happened is for science to find a way of downloading the contents of the “old” storage device – the left and right biological hippocampus (humans have one on each side of the brain – imagine 2x 2000gb storage devices with the ability to play video, audio and recover text through Google like searching and you have part of the functioning here). The intent is to add in the new device, minimizing damage to the old one.
Work is in progress on downloading the brain, at least according to Ray Kurzweil.
So, where will this all lead, I wonder…