Mouse
The technique used on the mice cannot be used on humans, at least for the time being. Photo by AP
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Israeli researchers have succeeded in erasing traumatic memories from the brains of mice, using a recently developed technique called optogenetics, which allows certain brain cells to be activated or deactivated through exposure to light.

The research team, headed by Dr. Inbal Goshen from the Edmond and Lily Safra Center for Brain Sciences in the Hebrew University of Jerusalem, examined mice that had been exposed to a process called “fear conditioning.” Placed in a certain environment, the mice were given electric shocks to their feet, eventually causing the specific environment to trigger a fear response whenever they were placed in it.

The researchers produced a light-sensitive protein that was genetically programmed to only affect brain cells with certain genetic traits. The protein was inserted into a harmless virus that was then injected into the hippocampus of the brain. The hippocampus plays an important role in controlling memory, and past studies have proved that new memories are also formed there – traumatic ones included. The mice’s brains were then penetrated and illuminated with an optical fiber. When the light-sensitive cells are exposed to light, the proteins can react by activating or deactivating the cells. In this case, the cells were deactivated.

If the mice’s brains were illuminated before they were placed in a fear-inducing environment – and remained lit throughout – the light deactivated the cells in the hippocampus that had been treated with protein, erasing the traumatic memory. As a result, there was no fear response.

The researchers also found that illuminating the cells in real time made the fear response disappear in mice that had been placed in the environment before the cells were deactivated.

The study used the new method to examine post-traumatic treatment. “The accepted working assumption is that memories cannot be controlled, as they are spread across different regions of the brain,” explains Goshen. “The method that was presented in the study allows the traumatic memory to be erased as it appears in real time. The findings have far-reaching implications, as today’s medications that affect regions of the brain – including regions that control memory – don’t work in real time like [the method] we demonstrated.”

However, the technique used on the mice cannot be used on humans at the moment, as long-term use of the viruses is not safe enough.

The study was conducted in cooperation with Prof. Karl Deisseroth from Stanford University, who developed the technique – called optogenetics – that allows certain brain cells to be activated or deactivated. His findings were recently published in the Cell scientific journal and will be presented this week at the Presidential Conference in Jerusalem.

Goshen’s team is continuing to develop treatments based on optogenetics, including the activation and deactivation of damaged star-shaped brain cells that have been diagnosed in sufferers of psychiatric and mental illnesses such as schizophrenia and depression.