Not one, but two studies in this month’s Nature Methods describe ways to control the brain and muscles of tiny organisms, including freely moving worms, using simple LCD projectors. This is part of the upcoming field of optogenetics, in which optical and genetic techniques are used together to directly influence brain circuits. They use this to study the brain’s pathways in live animals under controlled conditions.
Here’s from a Georgia Tech press release about worms controlled by an LCD projector:
The illumination system includes a modified off-the-shelf LCD projector, which is used to cast a multi-color pattern of light onto an animal. The independent red, green and blue channels allow researchers to activate excitable cells sensitive to specific colors, while simultaneously silencing others.
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.
Once Lu and her team built the prototype system, they used it to explore the “touch” circuit of the worm Caenorhabditis elegans by exciting and inhibiting its mechano-sensory and locomotion neurons. Alexander Gottschalk, a professor in the Johann Wolfgang Goethe-University Frankfurt Institute of Biochemistry in Frankfurt, Germany, and his team provided the light-sensitive optogenetic reagents for the Georgia Tech experiments.
For their first experiment, the researchers 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.
Additional experiments showed that the intensity of the light affected a worm’s behavior and that several optogenetic reagents excited at different wavelengths could be combined in one experiment to understand circuit functions. The researchers were able to examine a large number of animals under a variety of conditions, demonstrating that the technique’s results were both robust and repeatable.
The movies show coiling of the worm’s head in response to light leading to specific movement patters. Some pretty creepy stuff if you ask us.
Video of a head of a worm expressing light-sensitive optogenetic reagents:
Light from an LCD projector controlling the muscles of an immobilized worm:
Press release: Worm Remote Control: Researchers Use LCD Projector to Control Brain and Muscles of Tiny Organisms Such as Worms…
Study abstracts: Optogenetic manipulation of neural activity in freely moving Caenorhabditis elegans…, Real-time multimodal optical control of neurons and muscles in freely behaving Caenorhabditis elegans…
