Thanks for the Memories

fMRI

 

 

How easy is it to falsify memories? New research at the Weizmann Institute shows that a bit of social pressure may be all that is needed. The study, which appeared recently in Science, reveals a unique pattern of brain activity when false memories are formed – one that hints at a surprising connection between our social selves and memory.

The experiment, conducted by Prof. Yadin Dudai and research student Micah Edelson of the Institute’s Neurobiology Department, together with Prof. Raymond Dolan and Dr. Tali Sharot of University College London, took place in four stages. In the first, volunteers watched a documentary film in small groups. Three days later, they returned to the lab individually to take a memory test, answering questions about the film. They were also asked how confident they were about their answers.

They were later invited back to the lab to retake the test while being scanned in a functional magnetic resonance imager (fMRI) that revealed their brain activity. This time, the subjects were also given a “lifeline”: the supposed answers of the others in their film-viewing group (along with social-media-style photos). Planted among these were false answers to questions the volunteers had previously answered correctly and confidently. After seeing these “planted” responses, the participants conformed to the group, giving incorrect answers nearly 70% of the time.  

But were they simply conforming to perceived social demands, or had their memory of the film actually undergone a change? To find out, the researchers invited the subjects back to the lab to take the memory test once again, telling them that the answers they had previously been fed were not those of their fellow film watchers but random computer generations. In some cases the responses reverted back to the original, correct ones; but close to half remained erroneous, implying that the subjects were relying on false memories implanted in the earlier session.

An analysis of the fMRI data showed differences in brain activity between the persistent false memories and the temporary errors of social compliance. The most outstanding feature of the false memories was a strong co-activation and connectivity between two brain areas: the hippocampus and the amygdala. The hippocampus is known to play a role in long-term memory formation, while the amygdala, sometimes known as the emotion center of the brain, plays a role in social interaction. The scientists think that the amygdala may act as a gateway connecting the social and the memory processing parts of the brain; its “stamp” may be needed for some types of memories, to give them approval before they get uploaded to the memory bank. Thus social reinforcement could act on the amygdala, persuading our brains to replace a strong memory with a false one.

 

Prof. Yadin Dudai’s research is supported by the Norman and Helen Asher Center for Human Brain Imaging, which he heads; the Nella and Leon Benoziyo Center for Neurological Diseases; the Carl and Micaela Einhorn-Dominic Institute of Brain Research, which he heads; the Marc Besen and the Pratt Foundation, Australia; Lisa Mierins Smith, Canada; the Abe and Kathryn Selsky Memorial Research Project; and Miel de Botton, UK. Prof. Dudai is the incumbent of the Sara and Michael Sela Professorial Chair of Neurobiology.