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  • Squirming Under the Glare of Directed Light

Feb 2011
Lynn Savage,

There you are, a simple worm simply slithering along, when a light from above strikes part of your body. Suddenly, you start wriggling in a new direction – not one of your choosing. What has happened to your free will?

This sequence of images shows that, when researchers shine light onto the head of a worm expressing photosensitive proteins in its cells, the worm crawls in a triangular pattern. Courtesy of Hang Lu, Georgia Institute of Technology.

In the lab of Hang Lu, an associate professor in the Georgia Institute of Technology School of Chemical & Biomolecular Engineering in Atlanta, members of the worm species Caenorhabditis elegans are wondering just that – or would be if their brains were much, much larger. Their movement is being controlled by light originating from a common LCD projector.

Using light to control motion in lab animals is not new. The burgeoning field of optogenetics has several success stories of rats and other creatures having their neurons and muscle cells switched on and off by light. In every case, however, the light has been delivered via a fiber optic placed in the brain or by illuminating the animal’s entire body at once.

Lu and her colleagues, on the other hand, use an externally mounted LCD projector to deliver small swaths of light to precise areas on the body of the very tiny worm. As with animals in other optogenetic experiments, Lu’s worms have been genetically engineered to have photosensitive proteins as part of their sensory system. When blue, red or green light from the projector shines upon them, some neurons and muscles are activated while others are switched off, propelling the worms in any direction the researchers desire.

Lu’s team reported in the Jan. 9, 2011, online edition of Nature Methods that scanning the light along the worms’ bodies from head to tail caused backward movement when neurons near the head were activated and forward when neurons at the opposite end were stimulated. The investigators also found that the intensity of the light could affect the worms’ behavior.

Perhaps the next blockbuster science-fiction film could be about aliens who change our DNA so that we can be manipulated by lights emitted from their spacecraft. Or has that already been done?

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