How to Use Light to Control the Brain
Can a few neurons trigger a full memory? In a new study, published in Nature, a group of researchers from MIT showed for the first time that it is possible to activate a memory on demand, by stimulating only a few neurons with light, using a technique known as optogenetics. Optogenetics is a powerful technology that enables researchers to control genetically modified neurons with a brief pulse of light.
To artificially turn on a memory, researchers first set out to identify the neurons that are activated when a mouse is making a new memory. To accomplish this, they focused on a part of the brain called the hippocampus, known for its role in learning and memory, especially for discriminating places. Then they inserted a gene that codes for a light-sensitive protein into hippocampal neurons, enabling them to use light to control the neurons. With the light-sensitive proteins in place, the researchers gave the mouse a new memory. They put the animal in an environment where it received a mild foot shock, eliciting the normal fear behavior in mice: freezing in place. The mouse learned to associate a particular environment with the shock.