Looks like a flash of light can indeed be used to delete memories, according to scientists from the University of California, Davis.
By using light to erase certain memories in mice, researchers from the UC Davis Center for Neuroscience and department of psychology were able to prove the basic theory that different parts of the brain have to work together in order to retrieve episodic memories. They used optogenetics, a technique for studying and manipulating nerve cells with light, developed by Stanford University's Karl Deisseroth. The technique is fast becoming a standard for investigating the functions of the brain.
For around 40 years, neuroscientists have subscribed to the idea that episodic memories are retrieved through coordinated effort from the hippocampus and cerebral cortex. As the hippocampus is responsible for reproducing what is first learned through the cerebral cortex, losing function in the hippocampus can lead to the loss of years' worth of memories.
It wasn't until optogenetics was developed that scientists were able to test the idea directly.
Brian Wiltgen, Kazumasa Tanaka, and colleagues used genetically modified mice that had nerve cells that would fluoresce green when activated and would release a protein that would allow the cells to be turned off using light. Because of this, researchers were able to follow exactly which nerve cells in the hippocampus and cerebral cortex were being used and turn these off with light beamed via a fiber optic cable.
The mice had been trained, too, by getting mild electric shocks whenever they were placed in a cage. It's typical for mice to explore when placed in a new environment, but whenever they were placed in a cage where they have been shocked, they would freeze as a fear response.
When researchers turned off certain nerve cells in the hippocampus, the mice lost their memories of shock training, exploring as if they were seeing the cage for the first time.
"The cortex can't do it alone; it needs input from the hippocampus," Wiltgen said. "This has been a fundamental assumption in our field for a long time and Kazu's data provides the first direct evidence that it is true," said Wiltgen.
Other co-authors of the study include Jalina Graham, Yuki Nakazawa, Anahita B. Hamidi and Aleksandr Pevzner. Research for the study was made possible by grants from the National Science Foundation, Nakajima Foundation, McKnight Foundation and Whitehall Foundation.
