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| CREDIT: Brain image via Shutterstock |
When, as an adult, he returned to Alexandria, Egypt, where he lived as a
child, writer André Aciman felt he remembered everything; he could walk and
never get lost; he recognized the smells. But something was gone: a memory.
Aciman knew he had forgotten because, previously, he had written about
this one, a walk he had taken with his brother and their conversation, in a
draft of a memoir. "The editors said that brother of yours, he is one too
many children in this book," Aciman told the audience at a discussion about memory at the New
York Academy of Sciences on Wednesday (Nov. 14). "We changed that, and
some of the dialogue I had with him, I reconstructed so I was having an
internal dialogue with myself."
But upon returning to that street, he realized he had lost the memory of
the original conversation; the only record of it was now contained in his
draft, one overwritten by a desire for a better story. Aciman's memory no
longer told him which version was true.
Vulnerable memories
While most people do not write memoirs, and do not have editors
requesting revisions to their memories, the experience of the ephemeral and
sometimes illusory nature of memory is a familiar one. And Aciman's story came
as no surprise to the memory researchers on the panel. Flaws in memory
can arise at different points in the process, explained Daniel Schacter of
Harvard University. When someone first records a memory, the viewer incorporates
his or her own reactions and inferences about the event. As a result, the
viewer can color or distort the memory from the very beginning.
Other distortions can occur when a memory is retrieved. "When you
recall a memory, it is not just simply read out, you have to store and
consolidate [stabilize] it again," Schacter said. During this process, the
recalled memory becomes vulnerable to outside influences and can be distorted
by them. The physical basis for memory in the brain is not well understood.
Neuroscientists know the creation of memories does not require rewiring of the nerve cells, or
neurons, in the brain. Instead, memories are encoded by changes at synapses,
the junctions between neurons.
The reason for memory
While the fallibility of memory is impossible to escape, part of the
problem may be our perception of its purpose. "Even though we tend to
think about memory being all about the past, it is really all about helping us
prepare for the future," Schacter said. Some researchers think these
lapses are byproducts of memory functioning in ways evolution intended. For
instance, the vulnerability of retrieved memory may be a result of the brain’s
need to update memory and get rid of irrelevant information, he said.
Some false memories may have a similar explanation. Schacter, who has studied brain
activity related to true and false memories, demonstrated how easily memory
could be faked. He listed a string of words, beginning "candy, sour,
sugar, bitter, good…" Then he asked the audience to remember if a certain
word was part of the list. When asked if the word "sweet" was on the
list, the majority of the audience members raised their hands. "Sweet was
not on the list," Schacter said, explaining, "Most of the words are
related to sweet." In cases like this, the false memory may be a result of
the brain distilling the most relevant aspect of a memory, he said.
How technology defines memory
The idea of memory being continually constructed is not new, though it
has gained popular acceptance only in recent decades, said panelist Alison
Winter, a historian of science and medicine at the University of Chicago. Throughout
the ages, there has been a relationship between the recording technology
available and the perception of how the brain stores past experiences, Winter
said. For instance, wax tablets, once used as writing surfaces, provided a
metaphor for memories that soften and eventually blur over time.
Devices that record not only information but also the passage of time,
such as audio-recordings and film, made the idea of flashbacks, when someone re-experiences the past in real-time, a common one. "I am
curious if new digital technology has helped people think about memories in a
more constructive way," Winter said. Altering photographs and other
records, even before they are seen by anyone else, is now quick and easy. This
experience may give people a much more dynamic sense of how memories themselves
are stored, she said.
Erasing the bad
While some hope to improve their recall, others seek to erase. After work in his lab appeared to rewrite
rats' fearful memories, panelist Joseph LeDoux, a neuroscientist at New York
University, said researchers heard from people desperate for relief from
painful memories. Previous research had shown that injecting a drug that blocks
the formation of proteins could prevent the formation of new long-term memories
in the amygdala, a part of the brain associated with fear. But what about existing
memories?
To find out, LeDoux and his colleagues taught rats to associate a tone
with an electrical shock, as a result the rats became afraid of the tone. After
the fear memories were established, the researchers prompted the rats to recall
them by exposing the rats to the tone again, then they gave the animals the
drug. When the rats were tested the next day, they were no longer afraid of the
tone. "The idea is each time you take memory out, it becomes
vulnerable," LeDoux said. "There is a lot of debate about the
conditions under which this applies," he added.
Unfortunately for those seeking to erase bad memories, this work is not directly applicable to humans, he
cautioned. "When we do these kinds of experiments in animals we are
focusing on brain systems that work implicitly or unconsciously. … We are not
really looking at fear, we are looking at fear responses." In this case,
the researchers looked to see if the rats froze in response to the tone. Painful
human memories, such as those of combat veterans, cannot be erased, but rather,
research shows their emotional impact may be dampened, LeDoux said. This
panel discussion was part of a four-part series on consciousness, moderated by
Steve Paulson, of the public radio program "To the Best of Our
Knowledge" and presented by the Nour Foundation.
Source: Live Science
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