Some of Those Memories You’re Certain of May Be False: Study

A recent discovery offers valuable understanding about memory retrieval mechanisms and potential therapies for disorders such as PTSD.

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We all know the feeling: remembering an event so vividly, only to eventually realize it never actually happened. These illusory memories are more common than we may think.

A new study has uncovered distinct electrical patterns in the brain that set apart genuine memories from tricky false ones.

The discovery not only provides a rare glimpse into the mechanics of memory retrieval but also explores the possibilities for treating disorders such as post-traumatic stress disorder, which can cause intrusive flashbacks that seem real.

How the Hippocampus Shapes Our Recollections

The hippocampus is the brain’s memory hub and functions as an episodic memory system. Serving our long-term memory, it stores and retrieves personal experiences, along with associated details and emotions and ties them to context. False memories can occur if we recall an event without the original context.

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In the new study, published in Proceedings of the National Academy of Sciences, scientists from the University of Pennsylvania monitored hippocampal signals in patients before asking them to recall events.

They found that the neural patterns that emerged just before participants retrieved true memories were different from those that preceded the retrieval of false memories. The level of hippocampal activity also indicated the degree of similarity between factual and fabricated recollections.

Brain Signals That Reveal the Truth in Memories

Researchers recorded neural activity in epilepsy patients to precisely measure deep brain signals during memory formation and recall, according to the research paper’s lead author, Noa Herz, a postdoctoral fellow at the Department of Psychology at the University of Pennsylvania at the time of the study.

Participants memorized grouped or uncategorized items and later remembered them.

Direct intracranial recordings revealed that activity in the moments just before a memory is recalled predict its accuracy. Successful memory encoding and retrieval, indicated by increased high-frequency hippocampal activity and reduced low-frequency activity, differentiate true memories from false ones.

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This distinction occurs less than a second before recollection and fades quickly afterward.

Hippocampal Signals Shed Light on True and False Memory Resemblance

The study shows that reduced low-frequency activity in the hippocampus indicates a strong connection between remembered items and their context. A bigger reduction means a closer match between the recalled and actual contexts.

The extent of low-frequency reduction correlated to context similarity between true and false memories.

In controlled settings, researchers made people remember things that didn’t happen. They showed a list of related words but left out a crucial one. For example, words such as “dream,” “bed,” and “nap” were shown but not “sleep.” People might wrongly remember “sleep” because the other words make them think of it.

Using decoding techniques, the researchers also forecasted which context was linked to the remembered item. This sheds light on our ability to separate memories from distinct events.

Study Findings May Pave the Way for Novel Treatments

The findings enhance our understanding of memory retrieval mechanisms, Ms. Herz said in a statement. The study emphasizes the importance of predicting individual-level false memories, especially when they cause distress.

“Individuals suffering from stress-related psychopathology, such as post-traumatic stress disorder, often experience memory intrusions of their traumatic experiences under contexts that are safe and dissimilar to the traumatic incident,” the study authors wrote. “Targeted interventions that disrupt retrieval of intrusive memories could spawn novel therapies for such clinical conditions.”