Two independent studies just published (here and here, summarized here) have taken optogenetics to in vivo, free-moving C. elegans. One of the key technical advances is real-time registration of where the nematode is moving, which allows the microscopic stage’s motors to move, keeping the worm centered.
Liefer et al’s system has speed of ~50 frames per second and spatial resolution of ~30 μm, while Stirman et al’s system has a speed of ~25 frames per second and a spatial resolution of ~ 14 μm. Both papers demonstrate the precise control this offers researchers. For example, using different light sources to stimulate different types of neurons, or targeting spatially distinct regions of the body to target different cells.
When will we have a working model of the C. elegans nervous system? Not today, not tomorrow, but sometime sooner with this advance.
Brown and Schafer, 2011 Unrestrained worms bridled by the light, doi:10.1038/nmeth0211-129.
Leifer AM et al, 2011, Optogenetic manipulation of neural activity in freely moving Caenorhabditis elegans, doi:10.1038/nmeth.1554
Stirman JN et al, 2011, Real-time multimodal optical control of neurons and muscles in freely behaving Caenorhabditis elegans, doi:10.1038/nmeth.1555