Studying brain cells while controlling nerve cells with light is emerging as a new aid for brain scientists. The method, which is called optogenetics, is a biological technique that involves the use of light to control neurons that have been genetically modified to express light-sensitive ion channels.
In less than two decades, optogenetics has led to insights like how memories are stored, what creates perceptions, and what goes wrong in the brain during depression and addiction.
Last month, this technique was for the first time used to give a blind man some limited vision. The 58-year-old man has a genetic disease called retinitis pigmentosa, which causes light-gathering cells in the retina to die. Prior to the treatment, the man could detect some light, but couldn’t see motion or pick out objects. Now he can see and count objects and even reported being able to see the white stripes of the zebra crossing.
"So far, optogenetics research has taken place mostly in mice. But insights into more complex brains, including those of primates, may soon be found. We are definitely on the cusp of revealing some fascinating principles of the primate brain, such as how the brain transforms signals from the eyes into perceptions", Yasmine El-Shamayleh of Columbia University told the media.
Early signs of the potential of optogenetics reportedly emerged in 2004. Neuroscientist Ed Boyden was in a lab at Stanford checking on a dish of neurons that possessed a gene for an algal light sensor called channelrhodopsin-2. Boyden flashed blue light on the cells to see if they fired signals, and to his amazement, the very first cell he checked responded to the light with some spontaneous action.
Scientists have used optogenetics to make mice fight, mate, and eat, and even given blind mice sight.
This development has led to ongoing clinical trials in humans. Earlier this year, Sheila Nirenberg, a neuroscientist at Weill Cornell Medicine in New York City and founder of Bionic Sight, a company that is also using optogenetics to treat blindness, informed the media that blind people in her clinical trial could see light and motion after treatment.
"The results are preliminary. A full report from the clinical trial may be a year or more away", Nirenberg's company said in a press statement.