Memories

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Memories

 

Does your memory play tricks on you? New research may explain why this happens.

 

Memories-1Cited at: Miller G, "Making Memories," The Smithsonian, May, 2010.

 

Most people have so-called "flashbulb memories" of where they were and what they were doing when something momentous happened: their marriage, the death of a famous person, the 9/11 catastrophe, etc. But as clear and detailed as these memories feel, psychologists are finding that they are surprisingly inaccurate.

Dr. Karim Nader was interviewed heavily for this article. He is now a neuroscientist at McGill University in Monrtreal but he was a post-doctoral student in New York City on September 11, 2001. At the time of the attack, he was a researcher at New York University. He had flipped on the radio and heard of what was happening only two miles from where he was doing his research. Nader ran to the roof of his building where he had a clear view of the World Trade Towers. He stood there and watched them collapse.

Nader now says that his memory of the World Trade Center attack has played a few tricks on him. He disctinctly recalled seeing television footage on September 11 of the first plane striking the norther tower of the WTC.

Memories-2But, he was surprised to learn that such footage aired for the first time ever, the following day, September 12. It seems he was not alone: a 2003 study of 569 college students found that 73% of the respondants shared the exact same misperception.

(Dr. Nader seen at left)

Nader now believes he now has an answer for these odd quirks of memory. His ideas are unconventional within the neuroscience world but they have caused researchers to reconsider some of their most basic assumptions about how memory works. In short, Nader believes that the very act of remembering can change our memories. *Sounds like Quantum Theory- JH

Much of Nader's research is on rats, but he says the same basic principles apply to human memory as well. In fact, he says, it may be impossible for humans or any other animal to bring a memory to mind without altering it is some way.  For most people, the very idea that our memories are essentially malleable is a disturbing thought.

  

Memories-3Science has long known that recording a memory requires adjusting to commections between neurons. The memory storage part of the brain is an area called the hippocampus, seen at right in this graphic rendering. Each memory tweaks some tiny subset of the neurons in the brain (the brain has 100 billion neurons in all), changing the way they communicate. Neurons send messages to one another across the narraow gaps called synapses. A synapse is like a bustling port, complete with machinery for sending and receiving cargo - neurotransmitters, specialized chemicals that convey signals between neurons. All of the shipping machinery is built from proteins.

Eric Kandel is a neuroscientist at Columbia University and a fellow neurologist that has been hugely influencial in Nader's life. Kandel has shown how short-term memories - those lasting just a few minutes - involve relatively quick and simple chemical changes to the synapse that make it work more efficiently. Kandel, who shared the 2000 Nobel Prize in Physiology or Medicine, discovered that to build a memory that lasts hours, days or years, neurons must manufacture NEW proteins and expand the docks we spoke of earlier, to make the neurotransmitter traffic run more efficiently. Long term memories must, therefore, be built directly into the brain's synapses. Kandel and most other neuroscientists have generally assumed that once a memory is constructed, it is stable and can't be easily undone. The memory is thus "consolidated." According to this traditional view, the brain's memory system works something like a pen and a notebook. For a brief time, before the "ink" dries, it is possible to "smudge" what was written down. But, after consolidation, the memory changes very little. Barring Alzheimer's Disease and must plain old fashioned aging, the memory should stay the same - again, the traditional view of memories. Not so fast, says Nader.

Dr. Nader did a life-changing experiment some years ago. In the winter of 1999, he taught four rats that a high pitched beep preceeded a mild electric shock. That was the easy part - rodents learn such pairings after being exposed just once. Afterward, the rat freezes in place when it hears the tone. Nader then waited 24 hours, played the tone to reactivate the memory and injected into the rat's brain a drug that prevents neurons from making new proteins. Thus, if the consolidation theory was correct, and long term memories were more or less implanted to stay, the drug would have no effect on the rat's memory of the tone or the way it would respond to the tone. But, if memories have to at least partially "rebuilt" every time they are recalled, right down to synthesizing fresh proteins - rats given the drug might later respond as if they had never learned in the first place. It worked.

Memories-4 

(extreme close up of nerve synapses)

Further experiments continued. His collegues poo-poohed him but Nader continued with his firm belief that memories need to be at least partially "rebuilt" every time they are accessed. Interestingly, Nader's experiments struck a chord with psychologists who have long known that memories can be grossly distorted without people even realizing it.

As for dealing with Post Traumatic Stress Disorder patients, their memories must be housed the same way and if they need to be partially rebuilt on each recall, then those memories can be manipulated.

Among the questions facing Dr. Nader now is whether or not all memories become vulnerable when recalled or only certain memories under certain circumstances. The bigger question is, "Why are memories so unreliable?" This has been born out since time immemorial with testimony in court and depostions; people who truly believe what they are saying is true, are often rendering distorted versions of what they knew of saw.

Dr. Nader suggests that reconsolidation may be the brain's built in mechanism for recasting old memories in the light of everything that has happened since. In other words, it might be nature's way of keeping us from living in the past.

 

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