A community science group in Chile called Thinker Thing has used an EEG headset to move the leg of a cockroach. Among the mood-reading headbands and brain-controlled helicopters we’ve encountered in this blog, EEG-controlled roach legs are up there among the wilder uses we’ve seen for this emerging brain-to-world technology. 

Reuters visited Thinker Thing and interviewed Bryan Salt, the founder of the group, who described the setup. He used an EEG reader made by Emotiv to capture electrical signals from his brain. A software converted them into waveforms, certain frequencies of which were turned into electrical signals that got the roach leg kicking.

This makes sense when you consider that muscles—yours, mine, and those of the cockroach—are controlled by tiny bursts of current supplied by nerves, guided by electrical directions from our brains.

An amputated lone leg of a roach can be enervated by any electrical ping, if it’s at the right frequency, which is why the leg does a jig on a corkboard, separate from the anesthetized roach to which it belonged.

Thinker Thing is also building software that observes and “learns” which kinds of electrical signals are related to what kinds of motion in the leg, to be able to better control the induced movement. Thinker Thing tried out the moving roach setup at Hack Day in late October.

Backyard Brains, an educational group from California, has one of the more memorable demonstrations of the relationship between waveforms, electrical signals and disembodied roach legs. In a TedEd video (below) they pin electrodes onto a amputated roach leg to first listen in on electrical chitchat between neurons.

Then, reversing the direction of electrical signal sending, they cause the leg to twitch to the beat of song played on an iPhone.

For folks inspired to recreate the roach disco at home, Thinker Thing and Backyard Brains have created a device called SaltShaker which pipes in impulses derived from musical waveforms into the roach legs, while a camera records the twitches that result.