Altering Memories

March 21, 2014

By Medical Discovery News

In the film “Eternal Sunshine of the Spotless Mind,” people can request a medical procedure that targets memories pertaining to a specific subject or person and change or delete them. Several characters choose to have their memories of unrequited love and failed relationships erased. While the plot is purely fictional, new research does provide intriguing new details on how memories are stored, and how they might be manipulated.

Memories are stored in the temporal lobe and the hippocampus of the brain. Experiences produce physical and chemical changes in specific brain cells. Connections between brain cells that help with memory storage can also change. Scientists can identify the precise cells in a network involved with a specific experience. These are called memory traces or engrams.

Nobel Prize winner Susumu Tonegawa and his team wanted to explore how these memory traces are stored in cells. They used cells from the hippocampus that contained a light-sensitive protein called channelrhodopsin. When a memory pertaining to these cells is accessed within the brain, the light-sensitive protein activates. To discover which cells are associated with which memories, a memory is triggered and the cells respond with the light-sensitive protein. 

To do this experiment with mice, researchers assessed an easily observed behavior – the fear response. They first placed mice a chamber to allow memories of that environment to be formed. While this memory formed, channelrhodopsin was being produced in specific cells to record this memory. The next day the mice were placed in a completely different chamber and received a mild electric shock to their feet and a pulse of light simultaneously, prompting a fear response. But the pulse of light activated the memory of the chamber from the first day. And the following day when the mice were placed back in the first chamber, they displayed fear even though there was no electric shock associated with that chamber.

This means that activation of memory cells while receiving a shock in a different chamber produced fear associated with the first chamber. Now the mice connected the shock with the first chamber even though nothing bad happened there. This means scientist were able to implant a false memory by activating the trace of the original memory. This experiment identified the location of specific memories and showed that they could be manipulated. 

Not to sound too much like a sci-fi thriller, but this means in the future human memory may be able to be altered. There are positive, therapeutic applications, such as altering stress-inducing memories for war veterans with post-traumatic stress disorder. But in the wrong hands, this could be used for more sinister purposes, like mind control in “The Matrix.” Is it wise to alter any memories at all – does that change the person as a whole? Scientists and society will need to consider these questions if such experiments progress.  

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