Two-photon optogenetic tool promising for brain mapping

A researcher at the University of Texas at Arlington (UT Arlington) has developed a fiber-optic, two-photon optogenetic stimulator that could help scientists map and track the interactions between neurons inside different areas of the brain. The researcher who developed the tool—Samarendra Mohanty, an assistant professor of physics—previously discovered that near-infrared (NIR) light can be used to stimulate a light-sensitive protein introduced into living cells and neurons in the brain. The new method could show how different parts of the brain react when a linked area is stimulated.

The technology would be useful in the Brain Research Through Advancing Innovative Neurotechnologies (BRAIN) Initiative recently championed by President Barack Obama, Mohanty says. The initiative, if approved by Congress, would include $100 million in government investments in research.

Related: President Obama's BRAIN initiative could look to biophotonics techniques

“Scientists have spent a lot of time looking at the physical connections between different regions of the brain. But that information is not sufficient unless we examine how those connections function,” Mohanty says. “That’s where two-photon optogenetics comes into play. This is a tool not only to control the neuronal activity but to understand how the brain works.”

The two-photon optogenetic stimulation involves introducing the gene for channelrhodopsin-2 (ChR2), a protein that responds to light, into a sample of excitable cells. A fiber-optic IR beam of light can then be used to precisely excite the neurons in a tissue circuit.

In the brain, researchers would then observe responses in the excited area as well as other parts of the neural circuit. In living subjects, scientists would also observe the behavioral outcome, Mohanty says.

Optogenetic stimulation avoids damage to living tissue by using light to stimulate neurons instead of electric pulses used in past research. Mohanty’s method of using low-energy NIR light also enables more precision and a deeper focus than the blue or green light beams often used in optogenetic stimulation, according to their paper.

Using fiber-optics to deliver the two-photon optogenetic beam is another advance. Previous methods required bulky microscopes or complex scanning beams. Mohanty’s group is collaborating with UT Arlington Department of Psychology assistant professor Linda Perrotti to apply this technology in living animals.

Mohanty and his team's work appears in the journal Optics Letters; for more information, please visit http://www.opticsinfobase.org/ol/upcoming.cfm?page=2.

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