Planting Memories

Memory is fallible. Extensive research by Elizabeth Loftus illustrates how ineffectual people can be when it comes to recalling past events. Details of events can be obscured, omitted or altered. Additionally, this fragility ensures that memory is also very impressionable. People can be lead to recall scenarios in a certain way, and even entirely false memories can be assumed through suggestion alone. 

A potent example of the extent of the suggestibility of memory is the epidemic of false memories that occurred in the 1990s, whereby a large number of psychiatric patients reported memories of abuse, abduction and other traumatic childhood events that, for the most part, never actually took place. The recollection of these events was considered to be spurred on by intimations made by professional caregivers who interpreted dreams and patient statements to be representative of repressed childhood events. In some cases these recovered memories were quite literally unbelievable and featured events of satanic ritual or alien abduction - an extreme example of just how prone to manipulation memory can be.

A recent study illustrates that it is possible to implant false memories, not through the conventional means of suggestion, but biologically. Memories are represented in the brain as a distributed set of physical and chemical changes among a group of neurons. Optogenetics – a technique involving a combination of optics and genetics – allows for the real-time manipulation of this neural tissue. Previous work by this research group has demonstrated that optogenetics can successfully activate hippocampal cells by genetically encoding a protein that is responsive to light, channelrhodopsin. When cells with this protein are exposed to light they become activated.

The experiment placed mice in a test chamber and allowed them to freely explore. Exploring this new environment caused an increase in the production of the channelrhodopsin protein in the dentate gyrus of the hippocampus. The mice were then placed in a second environment and given a brief electric shock to serve as a conditioning fear-stimulus. As this was happening, their hippocampal cells were light-activated so as to surface memories associated with the first chamber. In the final stage of the experiment, the mice were returned to their initial environment. Here, they demonstrated typical fear response as if they had underwent the fear-stimulus in that environment although it never occurred.

This demonstration of false memory suggests its reliance on the same mechanisms that underpin the memory of real events. The fear-stimulus used in this experiment might be rather simplistic in comparison to an elaborate memory of satanic ritual, and indeed these results may only reveal the animal’s association of fear with a chamber similar to the fear-conditioned environment. However, it is still an interesting example of the potential to distort memory: to implant ideas and connotations that were never there to begin with and to have difficulty distinguishing them from reality.