Molecular “light switches” can reveal exactly which neurons are involved in creating a memory, allowing scientists to trigger that memory using only light.

This an example of how a novel technology called optogenetics being used by hundreds of labs is allowing scientists to tackle major unanswered questions about the brain, including the role of specific brain regions in the formation of memory, the process of addiction, and the transition from sleep to wakefulness.

To make neurons sensitive to light, scientists genetically engineer them to carry a protein adapted from green algae. When the modified neuron is exposed to light, via the fiber-optic implant, the protein triggers electrical activity within the cell that spreads to the next neuron in the circuit. The technology allows scientists to control neural activity much more precisely than previous methods.

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