File photo: The condition results in the disintegration of brain tissue due to an enzyme deficiency, which eventually leads to the build-up of toxic levels of sulphite in the body.

London - Scientists have successfully implanted false memories of an event that never happened into the brain, as part of a study showing how easy it is to create inaccurate recollections of what happened in the past.

The study is based on research into the memories of laboratory mice - but the scientists believe it could also explain false-memory syndrome in humans, such as cases where people honestly believe that something has happened even when they are told it did not.

False-memory syndrome is important in court cases that rely on the veracity of eyewitness accounts, which can be notoriously unreliable. Almost three-quarters of the first 250 convicted criminals in the US who were exonerated as a result of new DNA evidence, for instance, were originally convicted on the basis of eyewitness testimony.

“False memory in human often results from mixing different sources of information or confusing something thought or imagined with reality,” said Xu Liu of the Massachusetts Institute of Technology in Cambridge, Massachusetts, who was part of the research team.

“In our study we brought back an old memory in the mouse brain and artificially associated it with a real stimulus. Thus we generated a new memory for an event that never happened in reality. This illustrated one possible way false memory can form in humans.”

He added: “The technology we developed for this study allows us to dissect and even potentially to tinker with the memory process by directly controlling the brain cells.”

The study, published in the journal Science, used specially bred mice with a photosensitive pigment in their brains that stimulates the recovery of a genuine memory when the animals are exposed to a certain kind of light stimulus. This allowed the researchers to study nerve connections in the “memory cells” of a part of the mouse brain called the hippocampus. Pulses of light could be used to bring back genuine memories, as well as a false memory created by associating a true memory with the memory of a small but unpleasant electric shock. Using this approach, the scientists were able to implant the false memory of being in a box where the mice were given electric shocks even when this did not actually happen.

They also found that the neural connections made during the formation of a genuine memory were practically identical to those made during the formation of a false memory - suggesting a physical basis for false-memory syndrome. “We found that a false memory interacts with a true memory just like a regular memory. Also, the false memories activated the same region as true memories,” Dr Liu said. “Interestingly, sometimes people are more confident about false memories than true ones. Without outside references, a false memory is as real as a true memory to us.”

Although a pain stimulus was used in the experiment to stimulate the formation of a false memory in the mice about a fearful situation, the scientists believe other stimuli, such as a particular smell or taste, could be used to implant and recover a false memory in the human brain. - The Independent