World Science Festival: The Unbearable Lightness of Memory

Think about where you were on 9-11. Can you remember what you were doing before the attacks? Can you remember the room you were in when you found out what was happening, or who told you the news?

You are probably highly confident in these memories. But your recollections (and mine) are not nearly as accurate as we think they are, explained Elizabeth Phelps, a member of the Dana Alliance for Brain Initiatives and a lab director at New York University. Phelps was one of four neuroscientists who took part in a panel on the ways memory works (and doesn’t) at the World Science Festival this past weekend. 

Memories of events like 9-11, called flashbulb memories, are stored in the amygdala, an emotion-processing center of the brain particularly involved in fear. As Phelps explained, the amygdala focuses so heavily on emotions that it doesn’t store all the details about an event. But because our emotions are so involved in recalling flashbulb memories, we remain confident about them—this confidence spills over to poorly remembered details. Imaging studies have shown that when people think about 9-11, there is a great amount of activation in the amygdala, while activation of the parahippocampus, which is important to recalling detail, is low.

Why would our memories work this way? We need to be able to use our pasts to adapt in the future, explained Phelps. When there’s uncertainty, we may not be able to act until we get more information. But when we are confident we can act immediately, allowing ourselves to get out of potentially dangerous situations.

But our faulty recollections can have troubling consequences. As Dana Alliance member Daniel Schachter, the William R. Kenan, Jr. Professor of Psychology at Harvard and author of The Seven Sins of Memory, said, we sometimes combine the details of our experiences incorrectly. Schachter gave the example of Donald Thompson, a psychologist and memory expert, who was accused of a brutal rape. Fortunately for Thompson, he had an airtight alibi: He was giving a live television interview on unreliable memory when the crime occurred. The woman was watching the interview when she was raped, and had confused Thompson’s face with the rapist’s. This type of confident misattribution, said Schachter, is among the most frequent causes of wrongful convictions.

Our memories change every time we think about a past event. When our brains first lay down memories, they go through a consolidation process—before the process is completed, memories remain fragile (for more on this process, see “Long-term Memories: The Good, the Bad, and the Ugly,” a 2010 Cerebrum article). Every time we remember something, we have further opportunities to disrupt or update what we recall. Dana Alliance Member and University of Arizona Professor Lynn Nadel said that this process allows us to make memories more accurate as we add new information to them. Memory reactivation could strengthen, disrupt, or update our recollections, and could be used in treating people suffering from post-traumatic stress disorder.

When we retrieve memories and do nothing to lessen their impact, the fear becomes stronger, said Phelps. But when new information is added to the memory, a fear response can decline. Phelps’ lab taught study subjects to fear a blue square by administering a mild shock to the wrist each time the subjects saw the square. Later, when the subjects returned to the lab, researchers showed them the blue square a number of times without exposing them to a shock—the subjects no longer showed a fear reaction.

Chemical therapies could also someday lessen the negative emotional impact of memories. In 2006, Todd Sacktor, a professor at SUNY Downstate Medical Center, found that PKM zeta, a protein that catalyzes chemical reactions, is the molecule responsible for storing long-term memories. When researchers administer a zeta inhibitory peptide, or ZIP, to rats previously trained to avoid receiving a shock, the rats behave as they did prior to training; there is no evidence to the memory having been there. Alternatively, administering more PKM zeta can strengthen a memory.

It would be unethical to use ZIP on people—for one thing, researchers cannot target a specific memory, and so it would wipe out all long-term memories from a subject. As Phelps said, we are at least a decade away from translating these findings and others like them to treatments, but it will probably happen in our lifetime.

–Johanna Goldberg

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