Optogenetics is a technique that allows聽cells to be switched on and off with light.
The technique borrows cell proteins from algae, which respond to light and transport ions into and out of cells. When the genes for these proteins are inserted into neurons, they allow these cells to respond to light in the same way. A laser directed at neurons can activate them, or switch off their activity.
Karl Deisseroth at Stanford University and his colleagues were the first to trial this approach in 2004. Since then, Diesseroth, along with聽Ed Boyden, Feng Zhang and others, have honed the technique. They and others have used optogenetics to study how the brain works, how neurons might be controlled to treat disease, and even control an animal鈥檚 behaviour. Directing light at a particular set of brain cells can make mice run in circles, or monkeys look at a specific target, for example.
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The bulk of research so far has helped to elucidate how the brain, its networks and even individual neurons work. Optogenetics has helped researchers watch聽the birth of new neurons in a living brain for the first time, and see how聽memories in mice can be linked and uncoupled.
Deisseroth鈥檚 team has also used optogenetics to understand how anxiety and depression work in the brain. In experiments with mice, the team has identified brain circuits that seem to play a key role in these disorders. The same group has also located brain cells that might be best-targeted by deep-brain stimulation to treat Parkinson鈥檚 disease.
There鈥檚 hope that targeting neurons in this way could provide new treatments for epilepsy and chronic pain, too. Others are working on optogenetic applications to treat blindness in humans. Some degenerative eye diseases result from the loss of receptors in the retina that respond to light. Inserting the light-sensitive algae proteins into surviving cells could potentially restore sight. The approach聽 补苍诲听was first tested in a woman in 2016. A聽trial in 12 people in the UK聽was launched in 2018.
Optogenetics is also being explored as a technique to聽improve the effectiveness of cochlear implants聽for deafness. It聽appears to work in rats, and human trials are being planned.