Scientists Make Rats Forget and Remember With Light

No, they haven't invented the "Neuralyzer" from Men in Black, but it's pretty close. Scientists have successfully made genetically engineered lab rats forget and remember memories using a flash of light, revealing how memories are formed, according to a recent study.

The study, published in the journal Nature, details how a flash of light could be used to weaken or strengthen connections between neurons, effectively turning a memory on and off in the process.

This, researchers argue, is significant evidence supporting the theory that memories consist of specifically strengthened neural connections.

Thomas R. Insel, M.D., director of the National Institute of Mental Health (NIMH), said in a statement that this research could help scientists understand how symptomatic loss of memory, as seen in Alzheimer's disease, occurs.

"This improved understanding of how memory works may [also] hold clues to taking control of runaway emotional memories in mental illnesses, such as post-traumatic stress disorder," he added.

According to the study, researchers reached their findings after applying an optogenetic probing technique to the brains of lab mice. Optogentics uses the same cellular reactions that allow simple organisms like algae to react strongly to light.

In this study, the brains of lab rats were made light sensitive - controlling specific brain circuit components with a well-targeted and harmless laser.

These rats were then subjected to minor shocks accompanied with specifically aimed flashes of the laser into portions of their brain suspected to contain fear-memory related circuits.

Some of the rats received long-term potentiating (LTP) flashes, which encouraged stronger neural connections, while other rats received long-term depression (LTD) flashes, which countered the formation of strong connections theorized to be associated with memory formation.

Interestingly, the rats who received the LTP flashes appeared to become freighted and pained, being forced to remember the shock. While mice who received the LTD flashes were relaxed, not remembering the shock at all, even right after it occurred. Observed chemical changes in the rats' brains helped support these observations.

"In addition to eliminating any doubt about a link between LTP/LTD with memories, this work highlights the staggering potential of precision targeting and circuit manipulation for alleviating maladaptive memories," project officer Chiiko Asanuma said.

The researchers also suggest that weakening synapses in the brain, resulting in weakened neural connections, may explain a loss of memory experienced by Alzheimer's patients.

The study was published in Nature on June 1.