One day, Amelie discovers her apartment in an old rusty tin box, filled with childhood memories, guarded by a boy years ago. After locating the owner of the box, delivery. Upon opening the box discovered marbles and at that moment a sudden flash of childhood images flooded his mind and transport it to a time when he was in the schoolyard trying to fill their pockets with hundreds of marbles, while a teacher was screaming at him to hurry.

We've all experienced this feeling at some point, an object, a smell, a song or an old photograph transports us to another time and place. Now a group of neuroscientists have investigated if a few neurons can trigger all those memories.

In a new study, published in the journal Nature, a group of MIT researchers demonstrated for the first time that a memory can be activated on demand by stimulating a few neurons with light, using a technique known as optogenetics. Optogenetics is a powerful technology that uses light and genetically sensitive proteins to control cell activity.

They inserted a gene in mice, which encodes a light-sensitive protein in hippocampal neurons, which allow them to use light to control these neurons.

Then put the animal in a given environment in which he received a mild foot shock, causing the normal behavior in mice when they are afraid: they stay still. The mice learned to associate a particular environment, with that slight bump.

Later, to see if they could activate the memory, light activated with some of the neurons involved in memory and the animals showed a clear answer: the immobilization. Stimulation of neurons appeared to have activated the memory.

In 2010, the scientific method optogenetics was named the Year by the journal Nature. The technology was introduced in 2004 by a research group at Stanford University led by Karl Deisseroth, a collaborator in this research.

In recent years, has provided information optogenetics powerful in the neural basis of brain disorders such as depression, Parkinson's disease, anxiety and schizophrenia.

Not to worry, friends of conspiracy theories, by implanting memories and mind control, this technology is still far from being used in humans. However, the first steps towards clinical application of optogenetics already begun. A group of Brown University, for example, is working on an optical wireless electrode can "light" neurons. Who knows, someday we will have a new technology that allows us to erase bad memories or improve memory with a few sessions of light.