In a recent study, scientists from Harvard University, the University of Pennsylvania, and the Georgia Institute of Technology discovered that by shining a laser on particular neurons, they were able to control worms, encouraging them to move in varying directions and lay eggs. The published article, which appeared in Nature Methods, shows how it can be used to study how neurons generate locomotion or sense touch.
Andrew Leifer, a PhD student at Harvard who worked on the experiment, explained the interest in studying how a handful of neurons can work together in a circuit to generate behaviour. With that goal in mind, the research team developed the Controlling Locomotion and Behavior in Real Time (CoLBeRT) system, a new tool that allows light to stimulate or inhibit neurons in a worm as it moves.
Leifer worked with Christopher Fang-Yen, an assistant professor of bioengineering at the University of Pennsylvania, Aravinthan D. T. Samuel, a professor of physics, and Hang Lu, an associate professor of bio-molecular and chemical engineering, both from Harvard University.
The coworkers studied the nematode C. elegans, an optically transparent worm that is easy to manipulate since it only has 302 neurons—compared to over 100 billion present in a human brain.
“The general principle is that we give a worm genes to make its neurons light-sensitive,” Leifer said. “Then we can stimulate or inhibit those neurons by shining laser light on the worm. By watching how the worm responds we can learn about how those neurons generate the worm’s behavior.”
According to Leifer, the real trick was to build an instrument that would be fast enough to track the worm and shine laser light on only the neurons that interested the scientists. The difficulty was shooting at a moving target, which the CoLBeRT system simplified by taking a new picture of the worm, figuring out where the worm’s neurons are and re-aiming the laser every 20 milliseconds.
With these findings, scientists can develop a basic understanding of neural circuits in simpler creatures like worms and flies which may, according to Fang-Yen, eventually help us understand the human brain.
Samuel further celebrated the study and the technical advances that went into it.
“This optical instrument allows us to commandeer the nervous system of swimming or crawling nematodes using pulses of blue and green light [without] wires [or] electrodes,” he said. “We can activate or deactivate individual neurons or muscle cells, essentially turning the worm into a virtual bio-robot.”
But Adam Cohen, a Harvard assistant professor of physics, explained that while the CoLBeRT system is a convenient tool that will provide fundamental insights into how neural circuits work in a simple worm, similar technologies are not likely to be used in human minds.
“We don’t have to worry about laser mind control in people for quite a while, for two reasons. One, the worms had to be genetically modified to render their neurons sensitive to light. We can’t genetically modify people,” said Cohen. “And two, these worms are small and transparent, so it is easy to target an individual neuron in the freely behaving animal. People have opaque skulls and strongly scattering brain tissue, which would make optical targeting of single neurons extremely difficult.”
In response to possible concerns about future applications for human mind control, Leifer said there is nothing for people to be worried about.
“At the moment, the CoLBeRT system can only manipulate the neurons of genetically altered animals that are microscopic and transparent,” he said. “There is no need to worry about the CoLBeRT system ever controlling humans. You can leave your tinfoil hat at home.”