Editing Memory (NBS Senior Seminar Final Paper

Editing Memory

It selects, eliminates, alters, exaggerates, minimizes, glorifies and vilifies also, but in the end it creates its own reality, its heterogeneous but usually coherent version of events; and no sane human being ever trusts someone else's version more than his own. 

Salman Rushdie in Midnight's Children

     Our concept of memory is flawed.  Many of us imagine memories as accurate videos we have recorded of an experience and placed into a compartment of our brain to be called up at will.  Although memory remains a mysterious phenomenon, a more precise way of thinking about memory is as a process.  Memories are constantly changing, although as Salman Rushdie stated, we can’t help but trust our own memories to be realistic portrayals of the reality we experienced. An examination of alterations of memory, both by human design and due to disease, could shed on light on misconceptions about memory and other metaphors to use when explaining memory.  Two disorders, PTSD and persistent “déjà vecu,” particularly reveal ways in which our standard classifications of memory are inaccurate.  Treatments for the former also demonstrate some future avenues of neuroscience research on the topic of memory. 

            Post-traumatic stress disorder (PTSD) has a number of somatic symptoms such as dizziness, headaches and palpitations and is technically classified as anxiety disorder, although I would say that it shares many elements with memory disorders.  PTSD victims experience repeated episodes of “reliving” an event, flashbacks and dreams of an event.  PTSD reveals our lack of conscious control over aspects of memory and flaws in our definition of the separation between procedural and declarative memory.  We don’t consciously remember to turn our legs while biking or how to move our hand when writing words; muscle memory is a type of procedural memory.  Conversely, episodic memory is often defined as memories that are explicitly stored and retrieved. A memory of a traumatic event is episodic, yet individuals with PTSD do not explicitly retrieve the memory and instead can experience unwanted flashbacks.  Therefore, this distinction between explicit and implicit retrieval is not a true difference between declarative and procedural memory.  This is demonstrated in PTSD but I think people without neurological disorders can see variations in how much explicit recall is necessary to bring to mind procedural and declarative memories. 

            Another condition that reveals flaws in our compartmentalized thinking of memory and the categorizations we make between different types of memory is known as persistent “déjà vecu.”  Déjà vu is itself hazily defined; the accepted definition put forth in 1983 by Vernon Neppe is “any subjectively inappropriate impression of familiarity of the present experience with an undefined past” (Ratliff 2006).  Yet when this feeling is constant, what aspect in the memory process has gone awry?  The most logical and simple explanation is that déjà vu and persistent “déjà vecu” are different degrees of the same phenomenon.  Alan Brown describes 30 theories in his book “The Déjà Vu Experience” but they can be classified into four broader categories: “dual processing,” “neurological,” “memory” and “double perception.” 

            “Dual processing” likens memory to two video players.  The three processes are encoding, storage and retrieval.  One video player controls encoding and the other controls retrieval.  This type of error explains feelings of déjà vu as a switch of the active video player.  During encoding, the brain plays back sensations while they occur so reality feels like a memory.  “Neurological” errors are due to delays in electrical impulses so when there’s a pause between two sensations, the second sensation would feel like a memory.  The “memory” explanation most clearly demonstrates how little we know about déjà vu.  According to this theory, some element in the surroundings is familiar therefore an entire new place can seem familiar.  The example given is walking into a room with a chair similar to a chair in your grandmother’s living room, thus the entire situation has memory-like feelings.  The final theory is “double perception” and postulates that a lapse in attention occurs partway through taking in one’s surrounding so when attention is returned to the scene, it feels like a memory. 

            Unlike PTSD which has serious and drastic negative effects on a person’s life, persistent “déjà vecu” patients are anosagnosic- unaware of their condition.  That, along with our lack of deep understanding of the condition, contributes to the lack of treatments, even though the effects of those diagnosed with persistent “déjà vecu” are varied and can potentially affect large aspect of their lives.  A few case studied were mentioned in the article.  For example, M.A. no longer enjoyed newspapers and television because she found them overwhelmingly familiar and she stopped playing tennis because she claimed to know the outcome of every rally.  When shopping at the market, A.K.P. wouldn’t buy many items because he felt as though he had already bought the item the day before.  Still, these symptoms can be overlooked and do not impair daily life to the extent PTSD does. 

            PTSD, on the other hand, has many diverse treatment options.  One from the field of psychotherapy is called eye movement desensitization and reprocessing (EMDR) and has gained popularity in the past 15 years.  The treatment is similar to the tricks of hypnotists of old- a client watches the therapist’s back-and-forth finger movements.  Patients also learn to replace negative thoughts with positive ones.  This treatment was originally for dispelling the anxiety associated with PTSD but it has since been extended to a host of other conditions such as depression, sexual dysfunction, schizophrenia and eating disorders.  A critical essay in the Scientific American determined that while EMDR is better than no treatment or simply supportive listening, it is no better than standard behavior and cognitive-behavior therapies. 

            Another therapy that is currently still being researched is pharmaceutical and involves protein kinase MZeta (PKMzeta).  PKMzeta is necessary for long-term potentiation and zeta inhibitory peptide (ZIP) inhibits its effects.  Researchers found that if they inject mice with ZIP directly into their brain, mice forget learned behaviors such as the location of areas of the floor that give mild electric shocks.  One dose of ZIP was also found to be sufficient to make rats forget a disgust taste from three months earlier.  The type of memory “erased” in both experiments is an adversely conditioned association.  The effects of ZIP are also long-term as the researchers found that neophobia, an aversion to new stimuli or taste, was displayed to tastes a mouse had tasted months before if they were given ZIP in the interim.  Researcher also found that ZIP disrupts multiple associations therefore the lack of selectivity could be an issue in its use in humans.  Types of memory not affected by ZIP are global spatial information but precise spatial information is affected.  These distinctions and the fact that our understanding of memory doesn’t account for the mechanism by which PKMzeta can affect one type of spatial memory but not the other may indicate how far away we are from being able to use ZIP pharmaceutically. 

            Taking a creative leap into the non-immediate future, the use of ZIP to block PKMzeta in humans can have diverse and unexpected uses.  Obviously, dispelling negative associations would have benefits to individuals with PTSD.  These associations are often the source of the high unemployment rate in veterans, as they can’t function in environments that remind them of their combat experience.  For example, an exaggerated startle response from a car backfiring that sounds like a gunshot can be embarrassing in places of work.  ZIP could help people adjust to civilian life after traumatizing events, even without PTSD.  After a car accident, perhaps an immediate shot of ZIP to the brain may result in no increased anxiety from being in a car or driving the next day.  The experiment with novel tastes seemed to indicate most of the experience is “erased” but a critical clarification for the direction of the drug would be to what extent the entire memory is erased or if just the emotional association is lost.  Pain is necessary and has a purpose in preventing therefore the loss of these associations would be a problem our society would have to deal with. It could also make the drug popular with criminals.  A shot of ZIP and people may not remember being mugged or the negative association between a store and being held up there.  They may then repeatedly engage in behavior or habits that have been dangerous in the past.  ZIP in humans could erase fear and potentially help a number of anxiety or memory disorders but there are many negative repercussions to be considered for a drug with these capabilities. 

            Another issue with ZIP is the lack of selectivity but constraints in making this selective again reveal flaws in how we think about memory.  We can’t remove a memory the way we delete a file because blocking certain synapses will likely have effects on numerous memories.  A better way to think of memory is as a pattern of activation and each memory involves a different pattern but many of the same neurons are involved.  Until we can determine how to selective block synapses, targeting memories is far more difficult than culturally thought due to the pervasiveness of the “file folder” metaphor of memory. 

            Research on memory disorders and drugs like ZIP have a long road ahead as these studies and disorders continue to reveal flaws in how we think about memory.  Once we fully reject the idea of memories as accurate, static videos in our brain, we can attempt to help patients dissociate emotions from memories and retrieve memories they have lost to the years.

References

Carey, B. (2009, April 6).  Brain Researchers Open Door to Editing Memory.  The New York Times.  Retrieved from http://www.nytimes.com/2009/04/06/health/research/06brain.html

Ratliff, E. (2006, July 2).  Déjà Vu, Again and Again.  The New York Times.  Retrieved from             http://select.nytimes.com/preview/2006/07/02/magazine/1125013521013.html?scp=2&sq=ratliff%20deja%20vu&st=cse

Lilienfeld, S. and H. Arkowitz.  (2008, January 3).  EMDR: Taking a Closer Look.  Scientific American. Retrieved from http://www.scientificamerican.com/article.cfm?id=emdr-taking-a-closer-look