Researchers say they've been able to control the brains and muscles of small organisms such as worms, controlling them like tiny robots.
Using red, green and blue lights cannibalized from an ordinary LCD projector, the team was able to activate light-sensitive microbial proteins which were genetically engineered into the worms, allowing them to switch neurons and muscles on and off at will.
The independent red, green and blue channels allow researchers to activate excitable cells sensitive to specific colors, while simultaneously silencing others.
"This illumination instrument significantly enhances our ability to control, alter, observe and investigate how neurons, muscles and circuits ultimately produce behavior in animals," said professor Hang Lu of the Georgia Institute of Technology.
"Because the central component of the illumination system is a commercially available projector, the system's cost and complexity are dramatically reduced, which we hope will enable wider adoption of this tool by the research community."
By connecting the illumination system to a microscope and combining it with video tracking, the researchers are able to track and record the behavior of freely moving animals, while maintaining the lighting in the intended anatomical position. When the animal moves, changes to the light's location, intensity and color can be updated in less than 40 milliseconds.
Lu and her team have successfully used the system to explore the 'touch' circuit of the worm Caenorhabditis elegans by exciting and inhibiting its mechano-sensory and locomotion neurons.
For their first experiment, they illuminated the head of a worm at regular intervals while the animal moved forward. This produced a coiling effect in the head and caused the worm to crawl in a triangular pattern.
In another experiment, the team scanned light along the bodies of worms from head to tail, which resulted in backward movement when neurons near the head were stimulated and forward movement when neurons near the tail were stimulated.
They found that the intensity of the light affected a worm's behavior, and were able to reproduce the technique on a large number of animals under a variety of conditions.
"This instrument allowed us to control defined events in defined locations at defined times in an intact biological system, allowing us to dissect animal functional circuits with greater precision and nuance," says Lu.