Using optogenetics methods that control gene expression in the brains of living animals through a light source, researchers have controlled behavior in rodents and invertebrates. And now, scientists have extended the technique to primates as well, a critical step forward for greater optogenetic research that could one day lead to a better understanding of neurological processes and diseases in humans.
“That’s what you want to see…not just one or even a couple hundred neurons that have to change their activity to have a behavioral effect. You want to have a network of interconnected regions that change activity in a very dynamic way. That is what we saw,” said Vanduffel.
To begin, Vanduffel’s team mapped the brain circuitry of two rhesus monkeys activated during a series of simple peripheral eye-movement tasks using functional magnetic resonance imaging (fMRI). After establishing the activated brain areas during those saccadic tasks, the researchers injected light-activated proteins derived from algae using a viral vector into specific neurons within the mapped brain circuits. Using fMRI to implant optical fiber in targeted brain areas, the researchers could stimulate the neurons containing the light-activated protein code using pulses of blue light.
When Vanduffel and colleagues activated these neurons, they observed increased brain cell activity and improved eye-movement behavior in the monkeys during their saccadic tasks.
In time, the research may answer questions about neurological diseases related to the malfunctioning of specific cell types or circuits in the brain. "The more precisely you can manipulate these circuits, the better you may be able to alleviate the symptoms of the disease,” said Vanduffel.
But for right now, the researchers are planning to test more complex behaviors in primates as well as continue to improve the optogenetics technology. Also, Vanduffel’s lab is looking to target more specific cells instead of cell regions in order to better understand their individual significance.
“In the near future, it’s a fantastic new tool at the disposal of people that are investigating and trying to understand how the brain works,” he said. “With this technique you can really start manipulating activity of one very specific cell type amongst a sea of dozens and dozens of different cell types. There is no other technique that is able to do that.”
- Gerits, A., R. Farivar, B. R. Rosen, L. L. Wald, E. S. Boyden, and W. Vanduffel. 2012. Optogenetically induced behavioral and functional network changes in primates. Curr Biol (July).