How optogenetics is revolutionizing brain research

How is it possible to control neurons in a living brain with light?

At the center of this year's prize is a light-sensitive protein called channelrhodopsin-2, which was discovered by Peter Hegemann in the early 1990s in a type of algae (Chlamydomonas) that can sense light with its eyespot. When the light is strong enough, the algae swims towards the light. It turned out that the light-sensitive protein acts as an ion channel. It sits in the cell membrane and when it is hit by light, the protein opens up and lets ions into the cells. Georg Nagel identified the gene for the light-sensitive protein and when the psychiatrist Karl Deisseroth inserted it into nerve cells that he grew in a dish and exposed them to blue light, they reacted immediately. The light evoked a nerve signal that was transmitted to other nerve cells. In 2007, Karl Deisseroth succeeded in activating the nerve cells of living mice. In this way, they could control the movements of the mice's whiskers.

How does it help us understand the brain?

The ingenious thing is that the gene for the protein (the light-sensitive ion channel) can be transferred to individual nerve cells in a living brain with the help of a virus. The virus introduces the gene into the cells, which then start making the protein, which opens up the possibility of studying the brain in a whole new way. For example, you can stimulate certain nerve cells in the brain and see if it creates a certain behavior. Like sleep and wakefulness. There was previously a hypothesis that neurons in a certain part of the brain, the hypothalamus, control wakefulness. That they are what make us wake up. So what they did was they inserted ion channels into these cells and illuminated them, and then the animals woke up.

In what way can the discoveries alleviate disease and suffering?

The method is primarily a tool that increases our understanding of how the brain works. Both about the brain's normal functions and about the mechanisms behind diseases. Admittedly only in models, such as mice, but the mouse brain is very similar to our own brain. According to Professor Sten Linnarsson, vice chairman of the Nobel Committee, which appoints the prize winners, optogenetics has taught us a lot about how memories are formed in the brain, which is relevant for diseases where you have problems with memory, such as dementia. Examples of other diseases where optogenetics may be of great importance to our understanding of them are Parkinson's disease, addiction, depression, schizophrenia, autism and anxiety.