Dr. Christine Jurasinski
LabLearner Staff Scientist
How can you control brain activity? It’s a question that has fascinated us for centuries. Now, new research suggests that one way may lie with a strategy called optogenetics- the combination of optical and genetics techniques.
Neuroengineer Edward Boyden and his colleagues at MIT have recently discovered a way to use optogenetics to turn neurons within the brain on and off by simply exposing them to a certain wavelength of light. Their research has far reaching implications for the treatment of conditions such as epilepsy, chronic pain and post-traumatic stress disorder as well as providing a new way for understanding and studying cognition, emotion and other functions of the brain.
Boyden and his collaborators discovered a protein found in a special type of bacteria called archeabacteria that inhabits the Dead Sea. Archeabacteria are a type of bacteria that tend to inhabit extreme environments like hot springs, arctic environment, sulfurous springs or the high salt concentration of the Dead Sea.
The protein they discovered acts as a pump in cells, moving protons out of the cells when active. They also discovered that this protein, called the Arch protein, can be activated or turned on by light of yellow/green wavelength. Because protons carry a single positive charge, the movement of protons out of a cell changes the voltage within the cell. The inside of the cell becomes more negative as compared to the outside of the cell. As neurons work in part through electrical signals, changes in voltage are key to controlling their activity and their ability to fire and signal other neurons.
But, it’s what came next that illustrates that controlling the brain through light may not be as far off in the future as it seems. These researchers engineered the neurons of mice to produce the Arch protein. They then implanted a light source in the brain of the mice and found that when the Arch protein was activated in the neurons by the yellow/green light, it pumped protons outside the cells. As a result the voltage inside the neurons dropped and stopped them from firing! In essence the researchers were able to use light to stop neurons within the brain from firing, silencing an area of the brain.
Once the light was turned off, the Arch protein turned off and “reset” itself. Within seconds it was able to be activated by light again. Thus, a combination of yellow/green light and the Arch protein, acted as an “electrical switch” for neurons controlling their active and inactive state.
In addition to the Arch protein, Boyden and his colleagues have found several other proton pumps that respond to other wavelengths of light including those in the red and blue ends of the spectrum. What they hope is that by combining the different proteins and wavelengths of light different neurons and different areas of the brain could be controlled simultaneously.
How does this related to LabLearner students? Students in the LabLearner Program spend time in 4th and 6th grade studying the properties of light including how absorption and transmission of different wavelengths of light affect our perception of color and control biological processes such as photosynthesis. This new research shows that understanding light and its properties may be just as important in uncovering the processes of cognition, emotion and in treating brain disorders and diseases.
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