Giving the Ghost a Machine

Instead of using parts of natural brains to control robots, very few researchers are taking the opposite approach: using computer parts to control animals. This form of "remote control" mostly relies on basic conditioning paradigms, such as pairing certain responses of a rat to sensations with electrical stimulation, or relying on unconditioned stimuli like a cockroach's fear of light. Most explorations of neuron-to-silicon technology focus on brain-to-machine communication. The reverse - machine-to-brain communication - has garnered interest from DARPA and academia alike, though neuroengineering work with this focus is still rare.

In the May 2, 2002 issue of Nature, Talwar and colleagues from SUNY reported they could successfully train and wirelessly control rat behavior using brain microstimulation from up to 500m away. Rats were trained via positive reinforcement, in which rewards were delivered via electrical stimulation to the medial forebrain bundle, and cues were delivered via stimulation of the somatosensory cortical areas that normally receive input from the whiskers (a natural navigational guide in rats). After as little as ten training sessions, the rats were able to successfully navigate a variety of terrain, and remember the stimulus-response contingencies up to several months later. As they write, "the ability to receive brain activity remotely and interpret it accurately could allow a guided rat to function as both a mobile robot and a biological sensor." The researchers were not reluctant to point out the possible military applications for their work ("pest control, military surveillance, and mapping of underground areas," said Talwar), and therefore it is perhaps not surprising that little has since been published on the wireless control of small animals.

This and similar research had a long history of funding through DARPA's multidisciplinary "computational neuromechanics" grant (1998-2004). Some groundbreaking experiments by Miguel Nicolelis probably precipitated this funding. At Duke in the mid-90's, Miguel Nicolelis's team implanted electrodes in a rat whichi then underwent operant conditioning, where a lever press was paired with a drink of water. The electrodes recorded the activitiy of 46 motor cortex neurons, and the researchers then unpaired the lever with water, while a new contingency was put in place: the same 46 neurons had to be activated in order for the drink of water to be delivered. The rat soon learned to receive water through thought alone.

Despite the somewhat frightening implications this work, most of it has possible medical applications as well, such as the development of artificial prostheses. Several challenges remain for any attempt to implant electrode arrays for prolonged periods, however: the brain usually views these electrode arrays as foreign objects, and will attempt to expel them.