There is a long history of attempts at replicating neural systems either in software or in conventional semiconductors, such as the FACETS project (not to mention the creation of conventional logic gates from lab-grown biological neurons!) According to a USC Viterbi news release, researchers at the BioRC project, whose goal is research on an artificial cortex, have succeeded in creating a functioning synapse from carbon nanotubes.

The new research was presented by Alice C. Parker in the paper "A biomimetic fabricated carbon nanotube synapse for prosthetic applications" at the Life Science Systems and Applications Workshop in April 2011. (unfortunately the actual paper is behind a paywall but the abstract is readable). An earlier paper, "A Biomimetic Carbon Nanotube Synapse Circuit", describes the proposed design of synapse including schematics and comparison with biological neural components.

The BioRC project has been working on this project for a while. To learn more about their goals and history, see "Biomimetic Cortical Nanocircuits: The BioRC Project (PDF format)"

Ok, that's the end of the actual news. :) Because it's been a while since we had any really interesting articles on consciousness, I couldn't help letting my mind wander as I wrote this. As a result, I'm throwing in some personal ramblings and observations on this one.

A common objection raised to most previous software and hardware attempts at using Biomimetic neural technologies to build intelligent robots is the "not made of meat" argument. The reasoning, as I understand it, usually boils down to one of two complaints: 1) there is something magical/religious/spooky about meat that grants machines built from it conscious or 2) consciousness is a side-effect of the particular structure that evolved to implement meat-based intelligent.

Argument 1 is more common in my experience but argument 2 is the more serious complaint. The reasoning is that consciousness comes from the structure, rather than the function, of the machine. So it doesn't matter how well an artificial neuron executes its function, at least with regard to consciousness. If any part of the structure is missing (or "simulated" vs "real") then the entire system will not attain consciousness. Your robot will end up as smart and empty-headed as the philosopher's zombie.

A cognitive system implemented using silicon neural hardware is unlikely to be conscious by this reasoning, because at least some of the neural components are (considered by someone) to be mere "simulations" of their biological counter parts. And, of course, a cognitive system built using neural network software is right out (these folks usually argue that everything done on a computer, even basic math such as adding 2 plus 2, is merely a simulation and not real in the sense they wish it to be). The only thing that will satisfy them is a cognitive system based on hardware that has no component they deem as "simulated".

I think most of this line of reasoning is nonsense based on semantics. But, on the other hand, none of us really know what we're talking about until someone defines intelligence and consciousness in a meaningful way. So the significance of this debate should not be underestimated. After all, there have been entire theories of consciousness built around single neurons.

What's different here is that BioRC's approach is to build a fully functional neural structure in hardware using whatever materials are necessary. Whether the "meat" crowd will consider the BioRC hardware "real" enough to meet their requirements or whether they'll still find some portion of it to point to and say, "ah-ha, just a simulation!" remains to be seen. But it will be entertaining if not instructive to watch the further progress of the BioRC project and any possible practical applications of the hardware being developed.

I should also point out that most of this debate is going on among us spectators and is not really the main thrust of BioRC's research. Their reason for choosing carbon nanotubes over, say conventional CMOS circuits, is that the size and density of connections required to build a human-level cortex in CMOS would require decades to build and be prohibitively large. They hope carbon nanotubes offer a faster, smaller way to achieve that goal.