Sim-play: neural nets writ large (Image: Openworm)

THE Lego robot trundles forward, encounters a wall, stops, reverses. You might think there is nothing clever about that, except that this one has not been programmed to tell it when to stop and when to turn. Instead, it has an artificial brain precisely modelled on that of a nematode worm. WormBot is part of an effort to build the world’s first digital animal.

The quest to create such a creature is more than just a technical challenge. It will also pose some uncomfortable questions: if a digital model is an exact replica of a living animal, is it then alive?

The bot’s artificial brain has the same number of cells as a real nematode brain, and they are connected up in exactly the same way. But instead of a fluid tubular body animated by 95 muscles, WormBot has a plastic body and two wheels. It does not eat, defecate, reproduce or die. That will be left to its future sibling, WormSim, which will be a cell-for-cell digital copy of the worm, living inside a computer.


Both projects began with the simplest, smallest brain that we know of – the one that is inside the nematode worm Caenorhabditis elegans. This lab workhorse was the first organism to have its genome sequenced, and the first to have its entire brain mapped. It is largely hermaphrodite, with 959 cells each of which has also been mapped. Its network of 302 neurons connect via 6393 synapses – its connectome – and link to the worm’s 95 muscles at 1410 junctions.

This level of detail makes the worm an ideal candidate for a 3D avatar accurate down to the last cell. Earlier this year, the OpenWorm project was launched on Kickstarter to do just that. Already, researchers behind OpenWorm have created WormSim’s virtual brain and musculature, have linked them up, and are busy dropping it into virtual water to start fine-tuning its first strokes – nematode worms swim by undulating their 1 millimetre-long body. Sensory organs will come next. The worm should be ready for testing by next year. For an investment of $49, Kickstarter backers will get their own WormSim to play with on their computers. All of this data will be on an open source database, which has already provided the blueprint for WormBot’s brain.

There’s a long list of reasons for creating a virtual animal. “The mere act of trying to put a working model together causes us to realise what we know and what we don’t know,” says John Long, a roboticist and neuroscientist at Vassar College in New York State. Digital animals could complement and in some cases dispense with animal experiments. C. elegans is such a boon because it is so simple, yet 80 per cent of its genes are the same as ours. WormSim opens up the possibility of messing with a lab animal in ways that are not possible in the real thing.

Independent researcher Tim Busbice used the OpenWorm data to build WormBot’s brain. He started by building a neural network in which the neurons were connected to each other according to the C. elegans connectome. In a live animal, neurons often latch onto each other through repeated connections: so neuron A might make five synapses to neuron B, and each time A fires, all five relay the signal to B. Busbice used weightings to represent this in his neural network. Just like real neurons, those in WormBot, receive inputs from a network of “upstream” neurons and have to reach a threshold in order to fire and pass the signal on to those downstream. If that threshold isn’t reached a set period of time the system resets to zero.

Instead of muscles, WormBot has two wheels controlled by a matrix of 95 cells, representing the 95 muscles of C. elegans. Busbice hooked up the worm’s chemosensory neurons, which a real worm uses to detect smells and tastes, to a microphone that is triggered beyond a certain decibel threshold. He also connected the worm’s “nose-touch” neurons to a sonar that would send a message upstream to the brain if WormBot gets within 20 centimetres of an obstacle.

When all this was assembled, Busbice flipped the switch and began whistling, softly at first then louder and louder. Once his whistles got loud enough, the wheels were set in motion and WormBot moved towards the sound much as a real worm would be lured by the smells wafting from food.

WormBot moved towards the sound much as a real worm would be lured by the smells from food

When the bot came across a chair leg, its sonar picked up the obstacle, and without being programmed to do so, it stopped and reversed. “It’s only the connectome that makes it happen,” says Busbice.

“It’s very cool. I would not have guessed that this would have worked with minimal tuning,” says Murray Shanahan, a cognitive roboticist at Imperial College London.

Busbice has run rudimentary tests with his model. Previously, several teams of biologists have tweaked the brain of a real C. elegans by cutting specific neurons to see how this would change its behaviour. Busbice says he has done identical tests in his neural network, and watched his robot’s behaviour change in the same way as the live ones did.

This does not mean WormBot’s behaviour is intelligent, says Jürgen Schmidhuber of the Dalle Molle Institute for Artificial Intelligence Research in Manno, Switzerland. Its neural network is completely fixed. Intelligent living things learn from their experiences and these memories and new bits of information are encoded in their brains by strengthening or weakening existing connections, or forming new ones. This is way out of reach for Busbice’s creation.

It’s not, however, out of bounds for advanced editions of WormSim or future digital animals. And that raises all sorts of difficult philosophical questions.

“It’s an emotional and disturbing question,” says Shanahan. “Suppose you did this for the mouse, and it behaved in all the same ways as a real mouse does. Insofar as you know the real mouse can suffer, you have to ask yourself whether the virtual mouse does too.”

Assuming a neural network can learn and evolve just like a real organism, Schmidhuber says he doesn’t see a big difference between the two. “To me they are life,” he says. “And as they become more and more complex you start to have ethical questions, such as should you really turn off the computer.”

For many working in artificial intelligence the ethical questions are profound but they do not apply to WormBot – it’s too basic. Nor will they apply to the more sophisticated WormSims. Embodiment is essential – connecting up a virtual animal’s brain to all of its organs and sensors, says Shanahan. He adds that we are a long way from having an embodied mouse connectome, say, let alone anything else. Not only is computing power an issue (a mouse has 22 million neurons), we also don’t yet know enough about a mouse’s physiology to accurately model each cell.

Nevertheless, says Shanahan, WormSim throws the deep existential questions of embodied connectomes into the light. “I don’t think C. elegans is conscious, but if we really did build this for a mouse I can’t see any reason to deny suffering and consciousness to a synthetic copy,” he says. “It’s a deep philosophical question. I can’t think of a more important question.”

I can’t see any reason to deny suffering and consciousness to a synthetic copy of a mouse

Correction, 27 November 2014:Details of the WormSim project have been clarified since this article was first published.

This article appeared in print under the headline “Animal, digital, alive?”