Researchers from the Georgia Institute of Technology are
controlling the muscles and brain of tiny organisms through the use of liquid
crystal display (LCD) projector components.
Hang Lu, study leader and associate professor in the School of
Chemical and Biomolecular Engineering at the Georgia Institute of Technology,
along with graduate students Jeffrey Stirman and Matthew Crane, have used red,
green and blue lights from a LCD projector to switch neurons on and off inside freely
moving worms through light-sensitive microbial proteins that were genetically
engineered within these worms.
This new system consists of a modified LCD projector, a microscope, and video tracking.
The LCD projector sends a pattern of light onto the worm while the red, green,
and blue channels activate cells that react to each specific color.
This illumination system is then connected to a microscope and coupled with video
tracking in order to record the organism's movements and keep the light in
position. By doing this, the light's location, color and intensity changes as
the organism moves. These changes can be updated in 40 milliseconds or
"Because the central component of the illumination system is a
commercially available projector, the system's cost and complexity are
dramatically reduced, which we hope will enable wider adoption of this tool by
the research community," said Lu.
Lu and the research team began experimenting with the "touch
circuit" of the worm Caenorhabditis elegans to see if the illumination
system worked. The head of the worm was illuminated as it moved forward, which
resulted in a coiling effect where the worm moved in a triangular pattern. Then
the light was moved along the body from the head to the tail. When the neurons
in the head were "excited" by the light, the worm would move
backwards. When the light activated neurons in the tail, the worm moved
forward. Other variables changed the worm’s behavior as well, such as the
light's intensity and optogenetic reagents excited at different
"Experiments with this illumination system yield quantitative
behavior data that cannot be obtained by manual touch assays, laser cell ablation, or genetic
manipulation of neurotransmitters," said Lu.
In addition, the illumination system can heighten responses to
thermal, visual and chemical stimuli. The system is an important advancement in
optogenetics, allowing smaller animals to be controlled by light as well. Up
until now, systems like this only worked on larger animals.
"This illumination instrument significantly enhances our ability
to control, alter, observe and investigate how neurons, muscles and circuits
ultimately produce behavior in animals," said Lu.
This study was published in Nature Methods.