Lasers Control Nematode Worms Like Robots

Laura Sanders - scientists are using a dot of laser light. With it they can make a worm turn left, freeze or lay an egg. The researchers report their work online Jan. 16 in Nature Methods.

The new system, named CoLBeRT for “Controlling Locomotion and Behavior in Real Time,” doesn’t just create a mindless zombie-worm, though. It gives scientists the ability to pick apart complicated behaviors on a cell-by-cell basis.

“This system is really remarkable,” says biological physicist William Ryu of the University of Toronto, who was not involved in the research. “It’s a very important advance in pursuit of the goal of understanding behavior.”’

Transparent and small, the nematode Caenorhabditis elegans is particularly amenable to light-based mind control. Another benefit of the worm is that researchers know the precise location of all 302 of its nerve cells. But until now, there wasn’t a good way to study each cell by itself, especially in a wriggling animal.

“This tool allows us to go in and poke and prod at those neurons in an animal as it’s moving, and see exactly what each neuron does,” says study co-author Andrew Leifer of Harvard University.

The system is based on the emerging field of optogenetics, in which light is used to turn cells on or off. Leifer and his colleagues genetically engineered light-responsive molecules into particular groups of cells in the worm.

Then, a computer program that the team developed figures out where in the microscope’s field of view a target cell is. Once the cell is pinpointed, the program directs lasers so that a tiny beam of light hits the cell.

“When we’re shining light on a neuron, we’re hitting that neuron and nothing else,” Leifer says.

The whole process, from finding the cell to light hitting its target, takes about 20 milliseconds. As the worm’s position changes, that information is fed back into the computer program, and the laser is adjusted. If the worm crawls too far, a motorized microscope stage brings the animal back. ...

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