The nematode C. elegans shown here is expressing Channelrhodopsin in its HSN neurons (Pegl-6::ChR2::GFP). The worm has two HSN neurons that are located in the middle of the worm's body. As the worm swims, a narrow beam of blue light is scanned across the animal from its head to its tail. At frame 8828, the beam of light reaches HSN which induces the worm to lay eggs.
The transgenic worm was a gift from Niels Ringstad:
saturn.med.nyu.edu/research/mn/ringstadlab/See colbert.physics.harvard.edu for more.
This demonstrates the accuracy of the CoLBeRT system from the Samuel Lab at Harvard University from Leifer et al, "Optogenetic manipulation of neural circuits in freely moving Caenorhabditis elegans," Nature Methods, in press, 2011.