Creating a False Memory in the Brain of a Mouse

The Guardian (25^th July 2013) reports: 

“Scientists have implanted a false memory in the brains of mice in an experiment that they hope will shed light on the well-documented phenomenon whereby people “remember” events or experiences that have never happened.”

While this may seem like a claim out of science fiction, the article itself is a good example of science reporting.  The Guardian’s science correspondent, Alok Jha, provides a clear statement of the findings, and also sought out critical viewpoints from experts in the fields of memory and neuroscience.  In actual fact the technique used is somewhat similar to classical conditioning, such as the famous experiment of “Pavlov’s Dog”.  In this, an animal learned to associate a stimulus, such as the ringing of a bell, with the delivery of food.  In the end they would eventually salivate when the bell was rung even when no food was forthcoming.

Steve Ramirez, Xu Liu, Pei-Ann Lin, Junghyup Suh, Michele Pignatelli, Roger L. Redondo, Tomás J. Ryan, Susumu Tonegawa (2013). Creating a False Memory in the Hippocampus. Science, 341(6144), 387-391. doi: 10.1126/science.1239073

What was done:

This research was reported in Science.  The researchers used a technique known as optogenetics, where selected nerve cells in the brain can be genetically modified to become sensitive to light.  Specific cells in the hippocampus, an area of the brain associated with memory, were modified to express the light-sensitive protein channelrhodopsin-2 (ChR2).  The theory was that neurons associated with memories laid down while the mice explored a new environment would express this protein, and so these same memories could be reactivated by exposure to light.  In the next step of the experiment, the mice were subjected to tiny electric shocks to their feet, while these same memory-encoding cells were stimulated by shining light into the animal’s brain using implanted optical fibres.  As a result when these mice were placed back into the first chamber they showed a clear fear response suggesting a false association had been created between the electric shocks and the memory of this environment.  The implication is that memories can be created or developed through both internal and external processes.  As psychology research has long suggested, the act of remembering an event can be affected by external stimuli, leading to an alteration in the memory itself.  While this is a long way from actually creating what most of us would think of as a memory, it does demonstrate a new tool for investigating how our memories are formed.

Other uses of this technology:

Optogenetics is one of the most exciting areas of research in neuroscience and is leading to many advances in the study of the brain and nervous system.  In a recent article for Wired, Olivia Solon explored the exciting new area of “Electroceuticals” where, rather than using drugs to cure diseases, we would interact directly with the nervous system to control our body’s automatic systems.  This already happens to some extent with techniques like “deep brain stimulation” (DBS) for the treatment of neurological disorders such as Parkinson’s disease.  DBS uses electrodes implanted directly into the brain, which can cause unwanted side effects because the electrical signals can interfere with other parts of the nervous system.  The advantage of optogenetic technology is that specific cells can be targeted, reducing the possibility of negative side effects.