Who Do You Think You Are?
The young woman lies in a hospital bed, her head wrapped in bandages, a handsome man asleep at her bedside. She opens her eyes and we can immediately see her eyes move wildly around the room, taking in the surroundings with a panicked look on her face. The man jerks awake and tries to calm the frantic woman down, but she struggles against him. Nurses and doctors rush in as she starts yelling. “Who are you?” she screams over the chaos. “Who am I?”
Amnesia is one of the most popular tropes used in popular culture, and has become particularly synonymous with the melodrama of soap operas and romance novels (a personal favorite: Pregnesia by Carla Cassidy). But it should be no surprise that the amnesia that people come down with on TV is not exactly realistic. So when a psychologist or neuroscientist talks about someone with amnesia, what exactly are they referring to?
There are two main kinds of amnesia: organic amnesia and psychogenic (or dissociative) amnesia. Organic amnesia occurs when some damage to the brain itself results in memory loss, most often to an area called the medial temporal lobe that contains many structures critical for creating and storing memories. This memory loss includes being unable to recall past memories, called retrograde amnesia, and the inability to remember and learn new information, called anterograde amnesia (Squire and Alvarez 1995). Organic amnesia is very different from the kind usually portrayed on television. In the vast majority of cases, it takes more than a bump on the head to cause the extensive brain damage required for organic amnesia. It is also a permanent condition- patients with organic amnesia rarely regain the memories lost or the ability to form new memories. Even when they are able to learn new facts, they are unable to recall how or when they learned them (Bayley and Squire 2002).
In any neuroscience textbook, you are likely to come across a section devoted to one man- Henry Molaison. Molaison, who was known solely by the initials H.M. until his death in 2008, experienced severe seizures from the age of 10, possibly a consequence of a bicycle accident when he was 9 years old (Scoville and Milner 1957). His seizures grew worse as he got older and could not be controlled by medication. On September 1, 1953 he underwent surgery to remove a piece of brain tissue from his medial temporal lobes. The surgery reduced his seizure activity, but also left him with a severe case of organic amnesia (Scoville and Milner 1957). H.M.provided our first insight into the role that the medial temporal lobe plays in memory formation. While H.M. retained his intelligence, his emotional variability and his knowledge of his condition, he lost many of his memories from the years immediately prior to the surgery and never regained the ability to make new memories (Corkin et. al. 1997). Movies like “Memento” and “50 First Dates” have based their memory-impaired characters on H.M. After his death, H.M.’s brain was given to The Brain Observatory here at UCSD where it was sectioned and stained for further study.
Psychogenic amnesia more closely mimics the kind of amnesia usually portrayed on screen. The most common form is called transient global amnesia (or TGA) and occurs suddenly, with no immediately obvious cause (Bartsch and Deuschl 2010). TGA is most common in the 50-70 year age range, and has been known to occur following sudden emotional or psychological stressors. The exact cause of TGA is still unknown, although migraines, mild seizure activity and stroke-like conditions have been suggested (Romero et. al. 2013). Unlike those with organic amnesia, patients suffering from psychogenic amnesia exhibit exclusively retrograde amnesia, sometimes to the extent that they leave their homes and form a new identity (Markowitsch 2003). Also unlike organic amnesia, the vast majority of patients presenting with psychogenic amnesia eventually recover their identity and memories and return to their former lives, although they may be more prone to further psychological disturbances later in life (Bartsch and Deuschl 2010).
You may enjoy watching or reading about characters with amnesia, but can you imagine living with it? Benjaman Kyle is one of the most interesting cases of psychogenic amnesia in recent times. In 2004, Kyle was found beaten outside a Burger King in Richmond Hill, Georgia. It became quickly obvious that Kyle had little memory of who he was or how he came to be in Georgia. He recalls being born ten years before Michael Jackson (pinpointing his birthdate to be August 29, 1948), has memories of locations in Indianapolis and Denver, and insists that Benjaman is his first name. Since then local and state police as well as the FBI have contributed to the search for Kyle’s identity. He cannot recall his Social Security number, making it difficult for him to find a job, and efforts to search Social Security records to match him to known births has not turned up anything useful. This has led to him being listed as “missing” by the FBI, despite the fact that it is well-known that he is currently living in Georgia. Despite multiple TV and radio appearances, no one has stepped forward with any knowledge of Kyle’s former identity. You can learn more about Kyle and his story at Finding Benjaman.
Memory and Identity
On TV and in movies, a character with amnesia usually ends up searching for their identity. In the world of neuroscience, the term “amnesia” is associated with a loss of memory. But in fact, memory is crucially linked to our own concept of identity. Our memories are a history of who we were and what we did in the past, and they allow us to learn and grow as we create new memories in the future. In the end, maybe pop culture hasn’t gotten amnesia so wrong after all.
To find out more about amnesia in popular culture and media, go to TV Tropes’ list of Memory Tropes, but don’t blame us for the hours you lose reading up on all of them!
To read more about H.M. check out Dr. Suzanne Corkin’s book Permanent Present Tense.
Wondering what happened to H.M.’s brain? Check out this video to find out!
Larry R Squire and Pablo Alvarez; Retrograde amnesia and memory consolidation: a neurobiological perspective. Current Opinion in Neurobiology April 1995, 5(2):169–177
Peter J. Bayley and Larry R. Squire; Medial Temporal Lobe Amnesia: Gradual Acquisition of Factual Information by Nondeclarative Memory. The Journal of Neuroscience, 1 July 2002, 22(13): 5741-5748
William Beecher Scoville and Brenda Milner; Loss of Recent Memory After Bilateral Hippocampal Lesions. J Neurol Neurosurg Psychiatry 1957 20: 11-21
Suzanne Corkin, David G. Amaral, R. Gilberto González, Keith A. Johnson and Bradley T. Hyman; H. M.’s Medial Temporal Lobe Lesion: Findings from Magnetic Resonance Imaging. The Journal of Neuroscience, 15 May 1997, 17(10): 3964-3979
Thorsten Bartsch and Günther Deusch; Transient global amnesia: functional anatomy and clinical implications. The Lancet Neurology February 2010, 9(2):205–214
José Rafael Romero, Melissa Mercado, Alexa S. Beiser, Aleksandra Pikula, Sudha Seshadri, Margaret Kelly-Hayes, Philip A.Wolf and Carlos S. Kase; Transient global amnesia and neurological events: the Framingham Heart Study, Front Neurol. 2013, 4: 47
Hans J. Markowitsch; Psychogenic amnesia, NeuroImage, November 2003 20(S1):S132–S138
Such an interesting topic!
Dissociation is most obvious when it happens on a large, dramatic scale like Kyle’s, but what about specific or more restricted dissociation that seems to happen around particular life events such as a trauma? PTSD often seems to involve memory loss that’s described as dissociative, as do other forms of trauma. Is this considered to be a form of psychogenic amnesia? Are there theories related to amnesia that deal with why dissociative memory loss might happen after emotional or psychological trauma?
Hmmmm, good question! I mostly study organic amnesia but here’s my intuition- PTSD induced amnesia would, I imagine, be classified somewhat differently than transient global amnesia, which is the most common form of psychogenic amnesia. There’s a known cause when PTSD is involved, which is not the case in the vast majority of TGA cases.
I didn’t find many theories on why dissociative memory loss happens from a psychological point of view, mostly because I was looking in the neuroscience literature- and there aren’t many answers to why it happens from a neuro perspective. But I’ll definitely look into it!
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