How does the brain actually create a memory? Can we call up an absolutely pure memory like we do on the computer? Or is the act of remembering always to some degree recreating a new memory? What is the value of a good memory? If memory is the core of our self-identity, what will happen when scientists erase bad memories?
These were some of the questions that moderator Steve Paulson, executive producer of “To The Best of Our Knowledge” posed at the start of the second of the four-part lecture series entitled “The Merging Science of Consciousness: Mind, Brain and the Human Experience.” Presented by the Nour Foundation, Wisconsin Public Radio’s nationally syndicated program “To The Best of Our Knowledge,” and The New York Academy of Sciences, “The Mystery of Memory: In Search of the Past” featured psychologist Daniel Schacter (Harvard University), neuroscientist Joseph LeDoux (New York University), historian of science and medicine Alison Winter (University of Chicago), and novelist and comparative literature professor André Aciman (City University of New York Graduate Center) who contributed to a lively discussion of how memory impacts our perception of ourselves, the development of personality, and the ability to construct and reconstruct our past experience.
LeDoux provided the neuroscientific explanation: Memories are created through the process of learning utilizing the brain’s plasticity. Information travels through neural pathways reaching termination points. When something significant comes in and meets something else, it fires a connection. At these endpoints, the strength of connection will change. A memory is not a thing; it is a representation across many synapses that can be reactivated by a stimulus. “It’s amazing that it all works,” admitted LeDoux.
Schacter went on to describe the two types of memory — short-term memory that lasts for seconds, minutes and long-term memory. He mentioned that certain patient populations with brain damage lose one part and not the other. He alluded to H.M., the famous patient named Henry Molaison whose hippocampus and other parts of his brain were removed to alleviate his suffering from epilepsy, disrupting his short-term memory but not his long-term memories identifying himself.
In citing the two parts to memory — storage and recalling, Paulson intimated that there’s no such thing as calling back up a pure memory. He wondered if the problem was in the storage or the recall or both? Schacter answered that it can be in either, or both, depending on the circumstances. What’s coming in is interacting with what’s already there. Many times we record inferences so we could have a distorted memory from the beginning. Sometimes the distortions occur at the time of retrieval. Recalling a memory is not simply a read-out; it is actually a retelling, or reconsolidation.
Historian Alice Winters spoke of the changes in our notions of how we “record” memory. As long as we’ve had records, there has been great interest in how we record our memories. The ancients used a waxed tablet with the information blurring over time as the wax softened. Then came cameras and photographs which became the metaphor for how we record memory. The metaphor between external and internal storage of our life experience really took off when recording devices with playback came into play. In the cinema, these offer flashbacks which allow for the re-experiencing of the past in present time. With personal computers the storage of memory is much more dynamic.
Time to focus on the writer of the group. André Aciman, a memoirist and writer on memory, feels that the language of the computer is very dominent, particularly the feature, “Do you want to save this document? If you do, you will overwrite what you’ve written before.” In his memoir, he wrote about his childhood growing up in Alexandria, Egypt. When he went back, he remembered everything down to the smell of urine in the train stations. Except for a scene where he wrote about a walk he took with his brother. His editor at the time felt there were one too many children in the book and asked him to remove his brother. In the rewritten version he collapsed his brother’s voice into an internal voice. On his trip back to Egypt, when he walked down the particular street, he did not remember what had really happened. The only document he has of that memory is what he wrote the first time. In rewriting, he created a new memory. He doesn’t know which one is the true one. “I have forgotten what really happened there.”
Do neuroscientists have any tools for distinguishing between true and false memories? Schacter referred to scanners and the functional MRIs that measure blood flow in the brain when you perform do a certain task. These measure when participants recall a true or false memory. But how do you induce a false memory? We, the audience, were treated to the experience of taking a memory test.
Schacter read out a list of words. Hmmmmm, let me see if I can remember them. (Ha! I wrote quickly). Candy, sour, sugar, bitter, good, taste, tooth, nice, honey, soda, chocolate, art, cake, eat, high. In the experience, he explained, he would then put us in a scanner and give us the following memory test. He asked, “Was this word on the list? Taste.” We answered, “Yes.” Compliments to our memories. “How about ‘point’?” We answered “No.” Oh, we are very good. “How about ‘sweet’? How many people are sure ‘sweet’ is on the list?” We confidently answered, “Yes.” It turned out that “sweet” was not on the list. Much laughter. More than half of us thought that “sweet” was on the list. It seems that many of the words were related to “sweet”; this is one way a false memory is created, through association. In experiments, reliable similarities and differences in the activation maps of the brain scans point to which part of the brain is activated in the true and false memories.
What is the function of memory? It allows us to prepare for the future. Memory is not to reminisce. It evolved as a mechanism to store information to help adapt to the environment. Which begs the question: will we ever be able to erase bad memories, as in post-traumatic stress? According to LeDoux the research will lead to dampening the implicit unconscious responses of the brain when making impact to the memory. We will be able to dampen the emotions of the amygdala, but we will not be able to remove the memory.
What is the future of memory? These days when given a difficult question, we go to google. Will we value memory less and value forgetting more? Winter offered a humorous metaphor, “Is memory like leftovers from dinner? That you can make something with them the next day?” Schacter suggested that reconsolidation be considered as updating memory.
The final question in the question and answer period that followed the panel discussion came from a precocious 10-year old by the name of Lizzie. She wanted to know if the emotions you experience while you have a memory affect how you recall it? The example she gave was remembering something really sad while you’re in a good mood. Would it seem better to you or the same?
LeDoux answered that the context is going to change the experience you have and the way you’re going to interpret the memory. That might allow you to reconsolidate it or restore it so that the next time you remember it may change it as well. Clearly you’re as good as your last memory.