Using genetic tools, researchers engineered worms whose neurons gave off fluorescent light, allowing them to be tracked during experiments.
Researchers also altered genes in the worms that made neurons sensitive to light, meaning they could be activated with pulses of laser light (using optogenetics).
They discovered that controlling the dynamics of activity in just one interneuron pair (AIY) was sufficient to force the animal to locate, turn towards, and track virtual light gradients.
The largest challenges, though, came in developing the hardware necessary to track the worms and target the correct neuron in a fraction of a second.
“The goal is to activate only one neuron,” he explained. “That’s challenging because the animal is moving, and the neurons are densely packed near its head, so the challenge is to acquire an image of the animal, process that image, identify the neuron, track the animal, position your laser and shoot the particularly neuron — and do it all in 20 milliseconds, or about 50 times a second.
…The end result, he said, was a system capable of not only controlling the worms’ behavior, but their senses as well. In one test described in the paper, researchers were able to use the system to trick a worm’s brain into believing food was nearby, causing it to make a beeline toward the imaginary meal.